WO2008054045A1

WO2008054045A1 - Apparatus for combining and splitting wavelength band having three input and output ports

Info

Publication number: WO2008054045A1
Application number: PCT/KR2007/000255
Authority: WO
Inventors: Chang-Hee Lee; Ki-Man Choi; Sil-Gu Mun; Jung-Hyung Moon; Hoon-Keun Lee
Original assignee: Korea Advanced Institute Of Science And Technology
Priority date: 2006-10-31
Filing date: 2007-01-16
Publication date: 2008-05-08

Abstract

The present invention relates to an apparatus for combining and splitting wavelength bands having three input and output ports for bi-directional transmission. An apparatus for combining and splitting wavelength bands having three input and output ports for bi-directional transmission according to the present invention comprises two wavelength division multiplexing (WDM) filters, each of which splits X-band having a range of a first wavelength or less and Y-band having a range of a second wavelength or more from a wavelength band of light being transmitted though the three input and output ports; and one WDM filter for splitting one or more Z-bands having a range of a third wavelength within either X-band having the range of the first wavelength or less or Y-band having the range of the second wavelength or more. Alternatively, an apparatus for combining and splitting wavelength bands having three input and output ports for bi-directional transmission according to the present invention comprises one WDM filter for splitting X-band having a range of a first wavelength or less and Y-band having a range of a second wavelength or more from the wavelength band of light being transmitted; and two WDM filters, each of which splits one or more Z-bands having a range of a third wavelength within either X-band having the range of the first wavelength or less or Y-band having the range of the second wavelength or more.

Description

APPARATUS FOR COMBINING AND SPLITTING WAVELENGTH BAND HAVING THREE INPUT AND OUTPUT

PORTS

Technical Field

[1] The present invention relates to an apparatus for combining and splitting wavelength bands having three input and output ports for bi-directional transmission. More specifically, the present invention relates to an apparatus for combining and splitting wavelength bands having three input and output ports, which is capable of adding a new wavelength band for new bi-directional transmission and is necessary for combining with an existing wavelength band being transmitted bi-directionally through a one-line transmission path or for splitting from the existing wavelength band, while accommodating the existing wavelength band as it is. Background Art

[2] A need for broadband services is increased rapidly since the use of Internet has been increased and image and video oriented services have been generally used, and thus an interest has been focused on a metro/access network which connects a remote node to subscribers. In order for the metro/access network to meet the need of the subscribers for high-speed services, a method of accomplishing a high-speed must be done easily and at low costs to accommodate many subscribers. Thus, it is possible to make effectively a network to have a high-speed and to provide broadband services if a technology using a wavelength division multiplexing method is applied to the metro/ access network, because such technology is possible to transmit wavelength division multiplexed optical signals using a plurality of wavelengths, with the transparency of transmission methods and bit rate. As a one method of expanding the existing metro/ access network, a new wavelength band may be added as a transmission wavelength band, in addition to an existing wavelength band which has already been used. For doing so, a new wavelength band should be combined with or split from the existing wavelength band so that an apparatus for combining and splitting wavelength bands is required.

[3] An element such as add/drop multiplexers having a function of combining a signal with or splitting the signal from a predetermined wavelength in a transmission band has been used in the existing metro/access network. However, each add/drop multiplexer is required to be equipped with per each wavelength to be used for combining a signal having a new wavelength or splitting an existing signal in a prior art. Thus, such a requirement relating to add/drop multiplexers has a problem that it is cumbersome in terms of installation and costs should be necessarily increased due to the use of a plurality of add/drop multiplexers.

[4] In addition, the add/drop multiplexers of the prior art may combine and split only a signal having a predetermined specific wavelength. Thus, there is a problem that usability of the add/drop multiplexers has a certain limitation. Disclosure of Invention Technical Problem

[5] The object of the present invention is to solve the prior art problems and provide an optical passive element, which is capable of adding a new wavelength band for new bidirectional transmission and is necessary for combining with an existing wavelength band being transmitted bi-directionally through a one-line transmission path or for splitting from the existing wavelength band, while accommodating the existing wavelength band as it is. Technical Solution

[6] More specifically, according to a first aspect of the present invention, the present invention provides an apparatus for combining and splitting wavelength bands having three input and output ports for bi-directional transmission comprising: two wavelength division multiplexing (WDM) filters, each of which splits X-band having a range of a first wavelength or less and Y-band having a range of a second wavelength or more from a wavelength band of light being transmitted though the three input and output ports; and one WDM filter for splitting one or more Z-bands having a range of a third wavelength within either X-band having the range of the first wavelength or less or Y-band having the range of the second wavelength or more.

[7] According to a second aspect of the present invention, the present invention provides an apparatus for combining and splitting wavelength bands having three input and output ports for bi-directional transmission according to the first aspect of the present invention, wherein any two of the three input and output ports are respectively comprised of a first edge filter for splitting X-band having the range of the first wavelength or less and Y-band having the range of the second wavelength or more from the wavelength band of light being transmitted; and a second edge filter for splitting X-band having the range of the first wavelength or less and Y-band having the range of the second wavelength or more from the wavelength band of light being transmitted, and wherein one remaining input and output port is comprised of a coarse wavelength division multiplexing (CWDM) filter for splitting one or more Z-bands having the range of the third wavelength within Y-band having the range of the second wavelength or more.

[8] According to a third aspect of the present invention, the present invention provides an apparatus for combining and splitting wavelength bands having three input and output ports for bi-directional transmission comprising: one wavelength division multiplexing (WDM) filter for splitting X-band having a range of a first wavelength or less and Y-band having a range of a second wavelength or more from a wavelength band of light being transmitted though the three input and output ports; and two WDM filters, each of which splits one or more Z-bands having a range of a third wavelength within either X-band having the range of the first wavelength or less or Y-band having the range of the second wavelength or more.

[9] According to a fourth aspect of the present invention, the present invention provides an apparatus for combining and splitting wavelength bands according to the third aspect of the present invention, wherein any one of the three input and output ports is comprised of an edge filter for splitting X-band having the range of the first wavelength or less and Y-band having the range of the second wavelength or more from the wavelength band of light being transmitted, and wherein two remaining input and output ports are respectively comprised of a first coarse wavelength division multiplexing (CWDM) filter for splitting one or more Z-bands having the range of the third wavelength within Y-band having the range of the second wavelength or more; and a second CWDM filter for splitting one or more Z-bands having the range of the third wavelength within Y-band having the range of the second wavelength or more.

[10] Further features and advantages of the present invention can be obviously understood with reference to the accompanying drawings where same or similar reference numerals indicate same components.

Advantageous Effects

[11] An apparatus for combining and splitting wavelength bands having three input and output ports according to the present invention has the following advantages:

[12] 1. The present invention can be embodied at low costs and with a simple configuration so that it may function as the prior art add/drop multiplexers.

[13] 2. Unlike the prior art add/drop multiplexers which can combine and split only a signal with a specific wavelength, the present invention may combine a wavelength band having a certain range with or splitting it from an existing signal band so that high usability can be accomplished in the present invention.

[14] 3. The present invention may be utilized as an element for upgrading and expanding an existing metro network or an existing access network so that performance of an optical communications system can be enhanced at low costs.

[15] 4. The present invention may increase flexibility and expansibility of an existing metro network or an existing access network. Brief Description of the Drawings [16] Fig. 1 illustrates a general view of split bands of a wavelength division multiplexing filter and bi-directional wavelength bands for bi-directional transmission.

[17] Fig. 2 illustrates another general view of split bands of a wavelength division multiplexing filter and bi-directional wavelength bands for bi-directional transmission.

[18] Fig. 3 illustrates a first embodiment of an apparatus for combining and splitting wavelength bands according to the present invention for bi-directional transmission illustrated in Fig. 1.

[19] Fig. 4 illustrates a first alternative embodiment of an apparatus for combining and splitting wavelength bands according to the first embodiment of the present invention illustrated in Fig. 3.

[20] Fig. 5 illustrates a second alternative embodiment of an apparatus for combining and splitting wavelength bands according to the first embodiment of the present invention illustrated in Fig. 3.

[21] Fig. 6 illustrates a third alternative embodiment of an apparatus for combining and splitting wavelength bands according to the first embodiment of the present invention illustrated in Fig. 3.

[22] Fig. 7 illustrates a second embodiment of an apparatus for combining and splitting wavelength bands for bi-directional transmission according to the present invention illustrated in Fig. 1.

[23] Fig. 8 illustrates a first alternative embodiment of an apparatus for combining and splitting wavelength bands according to the second embodiment of the present invention illustrated in Fig. 7.

[24] Fig. 9 illustrates a second alternative embodiment of an apparatus for combining and splitting wavelength bands according to the second embodiment of the present invention illustrated in Fig. 7.

[25] Fig. 10 illustrates a third alternative embodiment of an apparatus for combining and splitting wavelength bands according to the second embodiment of the present invention illustrated in Fig. 7.

[26] Fig. 11 illustrates a third embodiment of an apparatus for combining and splitting wavelength bands for bi-directional transmission according to the present invention illustrated in Fig. 1.

[27] Fig. 12 illustrates a first alternative embodiment of an apparatus for combining and splitting wavelength bands according to the third embodiment of the present invention illustrated in Fig. 11.

[28] Fig. 13 illustrates a second alternative embodiment of an apparatus for combining and splitting wavelength bands according to the third embodiment of the present invention illustrated in Fig. 11.

[29] Fig. 14 illustrates a third alternative embodiment of an apparatus for combining and splitting wavelength bands according to the third embodiment of the present invention illustrated in Fig. 11. [30] Fig. 15 illustrates a fourth embodiment of an apparatus for combining and splitting wavelength bands for bi-directional transmission according to the present invention illustrated in Fig. 2. [31] Fig. 16 illustrates a first alternative embodiment of an apparatus for combining and splitting wavelength bands according to the fourth embodiment of the present invention illustrated in Fig. 15. [32] Fig. 17 illustrates a second alternative embodiment of an apparatus for combining and splitting wavelength bands according to the fourth embodiment of the present invention illustrated in Fig. 15. [33] Fig. 18 illustrates a third alternative embodiment of an apparatus for combining and splitting wavelength bands according to the fourth embodiment of the present invention illustrated in Fig. 15. [34] Fig. 19 illustrates a fifth embodiment of an apparatus for combining and splitting wavelength bands for bi-directional transmission according to the present invention illustrated in Fig. 2. [35] Fig. 20 illustrates a first alternative embodiment of an apparatus for combining and splitting wavelength bands according to the fifth embodiment of the present invention illustrated in Fig. 19. [36] Fig. 21 illustrates a second alternative embodiment of an apparatus for combining and splitting wavelength bands according to the fifth embodiment of the present invention illustrated in Fig. 19. [37] Fig. 22 illustrates a third alternative embodiment of an apparatus for combining and splitting wavelength bands according to the fifth embodiment of the present invention illustrated in Fig. 19. [38] Fig. 23 illustrates a sixth embodiment of an apparatus for combining and splitting wavelength bands for bi-directional transmission according to the present invention illustrated in Fig. 2. [39] Fig. 24 illustrates a first alternative embodiment of an apparatus for combining and splitting wavelength bands according to the sixth embodiment of the present invention illustrated in Fig. 23. [40] Fig. 25 illustrates a second alternative embodiment of an apparatus for combining and splitting wavelength bands according to the sixth embodiment of the present invention illustrated in Fig. 23. [41] Fig. 26 illustrates a third alternative embodiment of an apparatus for combining and splitting wavelength bands according to the sixth embodiment of the present invention illustrated in Fig. 23. Mode for the Invention

[42] Hereinafter, structures and functions of preferred embodiments in accordance with the present invention are described in more detail with reference to the appended drawings.

[43] An apparatus for combining and splitting wavelength bands having three input and output ports according to the present invention may be embodied by either a first type apparatus for combining and splitting wavelength bands having three input and output ports comprising a combination of a first and a second wavelength division multiplexing (WDM) filters, each of which has a function of splitting X-band and Y-band, and a third WDM filter having a function of splitting one or more Z-bands, which are a sub-band, within either X-band or Y-band, or a second type apparatus for combining and splitting wavelength bands having three input and output ports comprising a combination of a first and a second WDM filters, each of which has a function of splitting one or more Z-bands, which are a sub-band, within either X-band or Y-band, and a third WDM filter having a function of splitting X-band and Y-band. More specifically, the first and the second WDM filters may be embodied respectively by an edge-filter and the third WDM filter may be embodied by a coarse wavelength division multiplexing (CWDM) filter in the first type apparatus for combining and splitting wavelength bands. In addition, the first and the second WDM filters may be embodied respectively by a CWDM filter and the third WDM filter may be embodied by an edge-filter in the second type apparatus for combining and splitting wavelength bands.

[44] The apparatus for combining and splitting wavelength bands having three input and output ports according to the present invention as described above enables bidirectional transmission in at least four bands (either X-band, Z-band, Yl -band, Y2-band, or Y-band, Z-band, Xl -band, X2-band).

[45] Hereinafter, the present invention will be described in more detail with reference to the appended drawings.

[46] First, Fig. 1 illustrates a general view of split bands of a wavelength division multiplexing filter and bi-directional wavelength bands for bi-directional transmission, and Fig. 2 illustrates another general view of split bands of a wavelength division multiplexing filter and bi-directional wavelength bands for bi-directional transmission.

[47] Referring to Fig. 1, a case of bi-directional transmission is illustrated where bidirectional transmission is made by using X-band and Z-band, while Y-band is split into two bands (i.e., Yl -band and Y2-band) with split bands and bi-directional transmission bands of WDM filters for bi-directional transmission in four bands. In addition, referring to Fig. 2, a case of bi-directional transmission is illustrated where bi-directional transmission is made by using Y-band and Z-band, while X-band is split into two bands (i.e., Xl -band and X2-band) with split bands and bi-directional transmission bands of WDM filters for bi-directional transmission in four bands.

[48] In bi-directional transmission from Figs. 1 and 2 described above, wavelength transmission and reflection characteristics of a WDM filter may vary depending on the bands of bi-directional transmission which is desired to be used. Further, an edge-filter is used for a first and a second filters, respectively, each having a function of splitting X-band and Y-band, among WDM filters being used for bi-directional transmission from Figs. 1 and 2 described above, while a CWDM filter is used for a third and a fourth filters, respectively, each having a function of splitting one or more Z-bands, which are a sub-band, within either X-band or Y-band. In this case, a CWDM filter being used may be capable of splitting one or more Z-bands (Zl -band, Z2-band, ... etc.).

[49] Fig. 3 illustrates a first embodiment of an apparatus for combining and splitting wavelength bands according to the present invention for bi-directional transmission illustrated in Fig. 1.

[50] Referring to Fig. 3, an apparatus for combining and splitting wavelength bands according to a first embodiment of the present invention comprises a combination of a first and second edge filters, each for splitting X-band and Y-band from a wavelength band of light being transmitted, and a CWDM filter for splitting one or more Z-bands within Y-band. In an embodiment illustrated in Fig. 3, an upstream signal having a wavelength band with a range of 1260 ~ 1360 nm, which has already been used as a standard band in a time division multiplexing passive optical network (TDM-PON), is used as X-band, while a downstream signal having a wavelength band with the range of 1480 ~ 1500 nm within Y-band having a wavelength band of 1415 nm or more is used as Z-band. In this case, a downstream signal having a wavelength band with a range of 1550 ~ 1560 nm within Y-band may be added as Z2-band.

[51] More specifically, an apparatus for combining and splitting wavelength bands according to the present invention illustrated in Fig. 3 comprises a first edge filter for splitting X-band having 1360 nm or less and Y-band having 1415 nm or more from a wavelength band of light being transmitted; a second edge filter for splitting X-band having 1360 nm or less and Y-band having 1415 nm or more from the wavelength band of light being transmitted; and a CWDM filter for splitting Z-bands having a range of 1480 ~ 1500 nm and a range of 1550 ~ 1560 nm within Y-band having 1415 nm or more. In this first embodiment, a reflection port of the first edge filter is connected to a reflection port of the CWDM filter, while a pass port of the first edge filter is connected to a pass port of the second edge filter. In addition, a reflection port of the second edge filter is connected to a common port of the CWDM filter. In this case, each of the first and the second edge filters has a function of splitting a signal having a wavelength band (X-band) with 1360 nm or less among signals inputted into each common port through each pass port, and has a function of splitting a signal having a wavelength band (Y-band) with 1415 nm or more through each reflection port. Further, the CWDM filter outputs a signal having a wavelength band (Z-band) with the range of 1480 ~ 1500 nm and/or the range of 1550 ~ 1560 nm through its reflection port, while outputting a signal having a remaining wavelength band except Z-band through its common port. All of the first and the second edge filters and the CDWM filter used in Fig. 3 are a passive device and have a reciprocal characteristic. Thus, a Z-band signal with the rage of 1480 ~ 1500 nm and/or the range of 1550 ~ 1560 nm is transmitted along a path ® and an X-band signal having 1360 nm or less is transmitted along a path ® so that both the Z-band signal and the X-band signal may be used as bands for bi-directional transmission. Because an insertion loss of a reflection port is generally less than that of a pass port in a WDM filter, the Z-band signal with the rage of 1480 ~ 1500 nm and/or the range of 1550 ~ 1560 nm is designed to pass the reflection port. Yl -band and Y2-band, which may be used as another band for bi-directional transmission, are transmitted along a path ®. In this case, Yl -band and Y2-band can be respectively selected from anyone consisting a group of E-band (wavelength range: 1360 - 1460 nm), S-band (wavelength range: 1460 ~ 1530 nm), C-band (wavelength range: 1530 ~ 1565 nm), and L-band (wavelength range: 1565 ~ 1625 nm). Thus, any existing bi-directional signal is inputted into and outputted from the number one port (1) of an apparatus for combining and splitting wavelength bands having three ports according to the present invention as illustrated in Fig. 3 while any newly added bi-directional signals are inputted into and outputted from the number three port (3) thereof, and both any existing bi-directional signal and any newly added bi-directional signals are inputted into and outputted from the number two port (2) thereof. Further, because all of the first and the second edge filters and the CDWM filter illustrated in Fig. 3 are a passive device having a reciprocalcharacteristic, it should be fully understood by a person in the art that the Z-band signal with the rage of 1480 ~ 1500 nm and/or the range of 1550 ~ 1560 nm may be transmitted along a reverse direction of the path ® and the X-band signal having 1360 nm or less is transmitted along a reverse direction of the path ® so that both the Z-band signal and the X-band signal may be used as bands for bidirectional transmission, while Y l-band and Y2-band may be transmitted along a reverse direction of the path ®.

[52] Fig. 4 illustrates a first alternative embodiment of an apparatus for combining and splitting wavelength bands according to the first embodiment of the present invention illustrated in Fig. 3.

[53] More specifically, an apparatus for combining and splitting wavelength bands according to the first alternative embodiment of the first embodiment as illustrated in Fig. 4 illustrates a case that the functions of the pass port and the reflection port of the CWDM filter are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 3 so that the pass port of the CWDM filter in Fig. 3 is changed to a reflection port in Fig. 4, while the reflection port of the CWDM filter in Fig. 3 is changed to a pass port in Fig. 4. In this case, the CWDM filter outputs a signal having a wavelength band (Z-band) with the range of 1480 ~ 1500 nm and/or the range of 1550 ~ 1560 nm through the pass port, while outputting a signal having a remaining wavelength band except Z-band through the reflection port.

[54] Fig. 5 illustrates a second alternative embodiment of an apparatus for combining and splitting wavelength bands according to the first embodiment of the present invention illustrated in Fig. 3.

[55] More specifically, an apparatus for combining and splitting wavelength bands according to the second alternative embodiment of the first embodiment as illustrated in Fig. 5 illustrates a case that the functions of the respective pass ports and the respective reflection ports of the first and the second edge filters are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 3 so that each pass port of the first and the second edge filters in Fig. 3 is changed to a reflection port in Fig. 5, while each reflection port of the first and the second edge filters in Fig. 3 is changed to a pass port in Fig. 5. In this case, each of the first and the second edge filters has a function of splitting a signal having a wavelength band (X-band) with 1360 nm or less from a signal inputted into each common port through the reflection port, while having a function of splitting a signal having a wavelength band (Y-band) with 1415 nm or more therefrom through the pass port.

[56] Fig. 6 illustrates a third alternative embodiment of an apparatus for combining and splitting wavelength bands according to the first embodiment of the present invention illustrated in Fig. 3.

[57] More specifically, an apparatus for combining and splitting wavelength bands according to the third alternative embodiment of the first embodiment as illustrated in Fig. 6 illustrates a case that the functions of the respective pass ports and the respective reflection ports of the first and the second edge filters and the CWDM filter are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 3 so that each pass port of the first and the second edge filters and the CWDM filter in Fig. 3 is changed to a reflection port in Fig. 6, while each reflection port of the first and the second edge filters and the CWDM filter in Fig. 3 is changed to a pass port in Fig. 6. In this case, each of the first and the second edge filters has a function of splitting a signal having a wavelength band (X-band) with 1360 nm or less from a signal inputted into each common port through the reflection port, while having a function of splitting a signal having a wavelength band (Y-band) with 1415 nm or more therefrom through the pass port. In addition, the CWDM filter outputs a signal having a wavelength band (Z-band) with the range of 1480 ~ 1500 nm and/or the range of 1550 ~ 1560 nm through the pass port, while outputting a signal having a remaining wavelength band except Z-band through the reflection port.

[58] In the meanwhile, a filter for passing Z-band may be added between the first edge filter and the CWDM filter in Figs. 3 to 6, in order to reduce crosstalk of Yl -band and Y2-band which influences X-band and Z-band. In this case, the filter for passing Z- band may be embodied by a CWDM filter or a band-pass filter (BPF).

[59] Fig. 7 illustrates a second embodiment of an apparatus for combining and splitting wavelength bands for bi-directional transmission according to the present invention illustrated in Fig. 1.

[60] Referring to Fig. 7, an apparatus for combining and splitting wavelength bands according to a second embodiment of the present invention comprises a first CWDM filter for splitting Z-bands having a range of 1480 ~ 1500 nm and/or a range of 1550 ~ 1560 nm within Y-band having 1415 nm or more from a wavelength band of light being transmitted; an edge filter for splitting X-band having 1360 nm or less and Y- band having 1415 nm or more within the wavelength band of light being transmitted; and a second CWDM filter splitting Z-bands having the range of 1480 ~ 1500 nm and/ or the range of 1550 ~ 1560 nm within Y-band having 1415 nm or more. In this second embodiment, a reflection port of the first CWDM filter is connected to a reflection port of the second CWDM filter, while a pass port of the first CWDM filter is connected to a pass port of the edge filter. In addition, a reflection port of the edge filter is connected to a common port of the second CWDM filter. Referring to Fig. 7, an apparatus for combining and splitting wavelength bands according to the second embodiment of the present invention performs the same function as an apparatus for combining and splitting wavelength bands according to the first embodiment of the present invention as illustrated in Fig. 3.

[61] Fig. 8 illustrates a first alternative embodiment of an apparatus for combining and splitting wavelength bands according to the second embodiment of the present invention illustrated in Fig. 7.

[62] More specifically, an apparatus for combining and splitting wavelength bands according to the first alternative embodiment of the second embodiment as illustrated in Fig. 8 illustrates a case that the functions of the respective pass ports and the respective reflection ports of the first and the second CWDM filters are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 7 so that each pass port of the first and the second CWDM filters in Fig. 7 is changed to a reflection port in Fig. 8, while each reflection port of the first and the second CWDM filters in Fig. 7 is changed to a pass port in Fig. 8. In this case, each of the first and the second CWDM filters outputs a signal having a wavelength band (Z-band) with the range of 1480 ~ 1500 nm and/or the range of 1550 ~ 1560 nm through the pass port, while outputting a signal having a remaining wavelength band except Z-band through the reflection port.

[63] Fig. 9 illustrates a second alternative embodiment of an apparatus for combining and splitting wavelength bands according to the second embodiment of the present invention illustrated in Fig. 7.

[64] More specifically, an apparatus for combining and splitting wavelength bands according to the second alternative embodiment of the second embodiment as illustrated in Fig. 9 illustrates a case that the functions of the pass port and the reflection port of the edge filter are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 7 so that the pass port of the edge filter in Fig. 7 is changed to a reflection port in Fig. 9, while the reflection port of the edge filter in Fig. 7 is changed to a pass port in Fig. 9. In this case, the edge filter has a function of splitting a signal having a wavelength band (X-band) with 1360 nm or less from a signal inputted into the common port through the reflection port, while having a function of splitting a signal having a wavelength band (Y-band) with 1415 nm or more therefrom through the pass port.

[65] Fig. 10 illustrates a third alternative embodiment of an apparatus for combining and splitting wavelength bands according to the second embodiment of the present invention illustrated in Fig. 7.

[66] More specifically, an apparatus for combining and splitting wavelength bands according to the third alternative embodiment of the second embodiment as illustrated in Fig. 10 illustrates a case that the functions of the respective pass ports and the respective reflection ports of the first and the second CWDM filters and the edge filter are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 7 so that each pass port of the first and the second CWDM filters and the edge filter in Fig. 7 is changed to a reflection port in Fig. 10, while each reflection port of the first and the second CWDM filters and the edge filter in Fig. 7 is changed to a pass port in Fig. 10. In this case, each of the first and the second CWDM filters outputs a signal having a wavelength band (Z-band) with the range of 1480 ~ 1500 nm and/or the range of 1550 ~ 1560 nm through the pass port, while outputting a signal having a remaining wavelength band except Z-band through the reflection port. In addition, the edge filter has a function of splitting a signal having a wavelength band (X-band) with 1360 nm or less from a signal inputted into the common port through the reflection port, while having a function of splitting a signal having a wavelength band (Y-band) with 1415 nm or more therefrom through the pass port. [67] In the meanwhile, a filter for passing X-band may be added between the first

CWDM filter and the edge filter in Figs. 7 to 10, in order to reduce crosstalk of Yl -band and Y2-band which influences X-band and Z-band. In this case, the filter for passing X-band may be embodied by an edge filter or a band-pass filter (BPF).

[68] Fig. 11 illustrates a third embodiment of an apparatus for combining and splitting wavelength bands for bi-directional transmission according to the present invention illustrated in Fig. 1.

[69] Referring to Fig. 11, an apparatus for combining and splitting wavelength bands according to a third embodiment of the present invention comprises a first CWDM filter for splitting Z-bands having a range of 1480 ~ 1500 nm and/or a range of 1550 ~ 1560 nm within Y-band having 1415 nm or more from a wavelength band of light being transmitted; a second CWDM filter for splitting Z-bands having the range of 1480 ~ 1500 nm and/or the range of 1550 ~ 1560 nm within Y-band having 1415 nm or more from the wavelength band of light being transmitted; and an edge filter for splitting X-band having 1360 nm or less and Y-band having 1415 nm or more within the wavelength band of light being transmitted. In this third embodiment, a reflection port of the first CWDM filter is connected to a reflection port of the edge filter, while a pass port of the first CWDM filter is connected to a pass port of the second CWDM filter. In addition, a reflection port of the second CWDM filter is connected to a common port of the edge filter. Referring to Fig. 11 , it is fully understood that an apparatus for combining and splitting wavelength bands according to the third embodiment of the present invention performs the same function as an apparatus for combining and splitting wavelength bands according to the first and the second embodiments of the present invention as illustrated in Figs. 3 and 7, although the characteristic of the pass ports and the reflection ports in Fig. 11 has a reversed characteristic of the pass ports and the reflection ports in Figs. 3 and 7.

[70] Fig. 12 illustrates a first alternative embodiment of an apparatus for combining and splitting wavelength bands according to the third embodiment of the present invention illustrated in Fig. 11.

[71] More specifically, an apparatus for combining and splitting wavelength bands according to the first alternative embodiment of the third embodiment as illustrated in Fig. 12 illustrates a case that the functions of the respective pass ports and the respective reflection ports of the first and the second CWDM filters are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 11 so that each pass port of the first and the second CWDM filters in Fig. 11 is changed to a reflection port in Fig. 12, while each reflection port of the first and the second CWDM filters in Fig. 11 is changed to a pass port in Fig. 12. In this case, each of the first and the second CWDM filters has a function of splitting a signal having a wavelength band (Z-band) with the range of 1480 ~ 1500 nm and/or the range of 1550 ~ 1560 nm from a signal inputted into the common port through the reflection port, while having a function of splitting a signal having a remaining wavelength band except Z-band through the pass port.

[72] Fig. 13 illustrates a second alternative embodiment of an apparatus for combining and splitting wavelength bands according to the third embodiment of the present invention illustrated in Fig. 11.

[73] More specifically, an apparatus for combining and splitting wavelength bands according to the second alternative embodiment of the third embodiment as illustrated in Fig. 13 illustrates a case that the functions of the pass port and the reflection port of the edge filter are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 11 so that the pass port of the edge filter in Fig. 11 is changed to a reflection port in Fig. 13, while the reflection port of the edge filter in Fig. 11 is changed to a pass port in Fig. 13. In this case, the edge filter outputs a signal having a wavelength band (X-band) with 1360 nm or less through the pass port, while outputting a signal having a wavelength band (Y-band) with 1415 nm or more through the reflection port.

[74] Fig. 14 illustrates a third alternative embodiment of an apparatus for combining and splitting wavelength bands according to the third embodiment of the present invention illustrated in Fig. 11.

[75] More specifically, an apparatus for combining and splitting wavelength bands according to the third alternative embodiment of the third embodiment as illustrated in Fig. 14 illustrates a case that the functions of the respective pass ports and the respective reflection ports of the first and the second CWDM filters and the edge filter are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 11 so that each pass port of the first and the second CWDM filters and the edge filter in Fig. 11 is changed to a reflection port in Fig. 14, while each reflection port of the first and the second CWDM filters and the edge filter in Fig. 11 is changed to a pass port in Fig. 14. In this case, each of the first and the second CWDM filters has a function of splitting a signal having a wavelength band (Z-band) with the range of 1480 ~ 1500 nm and/or the range of 1550 ~ 1560 nm from a signal inputted into the common port through the reflection port, while having a function of splitting a signal having a remaining wavelength band except Z-band through the pass port. In addition, the edge filter outputs a signal having a wavelength band (X-band) with 1360 nm or less through the pass port, while outputting a signal having a wavelength band (Y-band) with 1415 nm or more through the reflection port.

[76] In the meanwhile, a filter for passing X-band may be added between the first

CWDM filter and the edge filter in Figs. 11 to 14, in order to reduce crosstalk of Yl -band and Y2-band which influences X-band and Z-band. In this case, the filter for passing X-band may be embodied by an edge filter or a band-pass filter (BPF).

[77] Fig. 15 illustrates a fourth embodiment of an apparatus for combining and splitting wavelength bands for bi-directional transmission according to the present invention illustrated in Fig. 2.

[78] Referring to Fig. 15, an apparatus for combining and splitting wavelength bands according to a fourth embodiment of the present invention comprises a combination of a first and second edge filters, each for splitting X-band and Y-band from a wavelength band of light being transmitted, and a CWDM filter for splitting one or more Z-bands within X-band. In an embodiment illustrated in Fig. 15, an upstream signal having a wavelength band with a range of 1300 ~ 1320 nm from an upstream signal having a wavelength band with a range of 1260 ~ 1360 nm, which has been already used as a standard band in a TDM-PON, is used as Z-band, while Y-band having a wavelength band of 1415 nm or more is used as a downstream signal. In this case, a signal having a wavelength band with a range of 1260 ~ 1280 nm within X-band may be added as Z- band.

[79] More specifically, an apparatus for combining and splitting wavelength bands according to the present invention illustrated in Fig. 15 comprises a first edge filter for splitting X-band having 1360 nm or less and Y-band having 1415 nm or more from a wavelength band of light being transmitted; a second edge filter for splitting X-band having 1360 nm or less and Y-band having 1415 nm or more from the wavelength band of light being transmitted; and a CWDM filter for splitting Z-band having a range of 1300 ~ 1320 nm within X-band having 1360 nm or less. In this fourth embodiment, a reflection port of the first edge filter is connected to a reflection port of the CWDM filter, while a pass port of the first edge filter is connected to a pass port of the second edge filter. In addition, a reflection port of the second edge filter is connected to a common port of the CWDM filter. In this case, each of the first and the second edge filters has a function of splitting a signal having a wavelength band (X-band) with 1360 nm or less among signals inputted into each common port through each reflection port, while having a function of splitting a signal having a wavelength band (Y-band) with 1415 nm or more among signals inputted into each common port through each pass port. Further, the CWDM filter outputs a signal having a wavelength band (Z-band) with the range of 1260 ~ 1280 nm and/or the range of 1300 ~ 1320 nm through its reflection port, while outputting a signal having a remaining wavelength band except Z-band through its pass port. All of the first and the second edge filters and the CDWM filter used in Fig. 15 are a passive device and have a reciprocal characteristic. Thus, a Z-band signal with the rage of 1260 ~ 1280 nm and/or the range of 1300 ~ 1320 nm is transmitted along a path ® and a Y-band signal having 1415 nm or more is transmitted along a path © so that both the Z-band signal and the Y-band signal may be used as bands for bi-directional transmission. In addition, Xl-band and X2-band, which may be used as another band for bi-directional transmission, are transmitted along a path ®. In this case, Xl-band and X2-band can be respectively selected from a wavelength of O-band (wavelength range: 1260 ~ 1360 nm). Thus, any existing bi-directional signal is inputted into and outputted from the number one port (1) of an apparatus for combining and splitting wavelength bands having three ports according to the present invention as illustrated in Fig. 15 while any newly added bidirectional signals are inputted into and outputted from the number three port (3) thereof, and both any existing bi-directional signals and any newly added bi-directional signals are inputted into and outputted from the number two port (2) thereof. Further, because all of the first and the second edge filters and the CDWM filter illustrated in Fig. 15 are a passive device having a reciprocalcharacteristic, it should be fully understood by a person in the art that the Z-band signal with the rage of 1260 ~ 1280 nm and/or the range of 1300 ~ 1320 nm may be transmitted along a reverse direction of the path ® and the Y-band signal having 1415 nm or more is transmitted along a reverse direction of the path © so that both the Z-band signal and the Y-band signal may be used as a band for bi-directional transmission, while Xl-band and X2-band may be transmitted along a reverse direction of the path ®.

[80] Fig. 16 illustrates a first alternative embodiment of an apparatus for combining and splitting wavelength bands according to the fourth embodiment of the present invention illustrated in Fig. 15.

[81] More specifically, an apparatus for combining and splitting wavelength bands according to the first alternative embodiment of the fourth embodiment as illustrated in Fig. 16 illustrates a case that the functions of the pass port and the reflection port of the CWDM filter are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 15 so that the pass port of the CWDM filter in Fig. 15 is changed to a reflection port in Fig. 16, while the reflection port of the CWDM filter in Fig. 15 is changed to a pass port in Fig. 16. In this case, the CWDM filter outputs a signal having a wavelength band (Z-band) with the range of 1260 ~ 1280 nm and/or the range of 1300 ~ 1320 nm through the pass port, while outputting a signal having a remaining wavelength band except Z-band through the reflection port.

[82] Fig. 17 illustrates a second alternative embodiment of an apparatus for combining and splitting wavelength bands according to the fourth embodiment of the present invention illustrated in Fig. 15.

[83] More specifically, an apparatus for combining and splitting wavelength bands according to the second alternative embodiment of the fourth embodiment as illustrated in Fig. 17 illustrates a case that the functions of the respective pass ports and the respective reflection ports of the first and the second edge filters are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 15 so that each pass port of the first and the second edge filters in Fig. 15 is changed to a reflection port in Fig. 17, while each reflection port of the first and the second edge filters in Fig. 15 is changed to a pass port in Fig. 17. In this case, each of the first and the second edge filters has a function of splitting a signal having a wavelength band (X-band) with 1360 nm or less from a signal inputted into each common port through the pass port, while having a function of splitting a signal having a wavelength band (Y-band) with 1415 nm or more therefrom through the reflection port.

[84] Fig. 18 illustrates a third alternative embodiment of an apparatus for combining and splitting wavelength bands according to the fourth embodiment of the present invention illustrated in Fig. 15.

[85] More specifically, an apparatus for combining and splitting wavelength bands according to the third alternative embodiment of the fourth embodiment as illustrated in Fig. 18 illustrates a case that the functions of the respective pass ports and the respective reflection ports of the first and the second edge filters and the CWDM filter are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 15 so that each pass port of the first and the second edge filters and the CWDM filter in Fig. 15 is changed to a reflection port in Fig. 18, while each reflection port of the first and the second edge filters and the CWDM filter in Fig. 15 is changed to a pass port in Fig. 18. In this case, each of the first and the second edge filters has a function of splitting a signal having a wavelength band (X-band) with 1360 nm or less from a signal inputted into each common port through the pass port, while having a function of splitting a signal having a wavelength band (Y-band) with 1415 nm or more therefrom through the reflection port. In addition, the CWDM filter outputs a signal having a wavelength band (Z-band) with the range of 1260 ~ 1280 nm and the range of 1300 ~ 1320 nm through the pass port, while outputting a signal having a remaining wavelength band except Z-band through the reflection port.

[86] In the meanwhile, a filter for passing Z-band may be added between the first edge filter and the CWDM filter in Figs. 15 to 18, in order to reduce crosstalk of Xl -band and X2-band which influences Y-band and Z-band. In this case, the filter for passing Z-band may be embodied by a CWDM filter or a band-pass filter (BPF).

[87] Fig. 19 illustrates a fifth embodiment of an apparatus for combining and splitting wavelength bands for bi-directional transmission according to the present invention illustrated in Fig. 2.

[88] Referring to Fig. 19, an apparatus for combining and splitting wavelength bands according to a fifth embodiment of the present invention comprises a first CWDM filter for splitting Z-bands having a range of 1260 ~ 1280 nm and a range of 1300 ~ 1320 nm within X-band having 1360 nm or less from a wavelength band of light being transmitted; an edge filter for splitting X-band having 1360 nm or less and Y-band having 1415 nm or more within the wavelength band of light being transmitted; and a second CWDM filter splitting Z-bands having the range of 1260 ~ 1280 nm and/or the range of 1300 ~ 1320 nm within X-band having 1360 nm or less. In this fifth embodiment, a reflection port of the first CWDM filter is connected to a reflection port of the second CWDM filter, while a pass port of the first CWDM filter is connected to a pass port of the edge filter. In addition, a reflection port of the edge filter is connected to a common port of the second CWDM filter. Referring to Fig. 19, an apparatus for combining and splitting wavelength bands according to the fifth embodiment of the present invention performs the same function as an apparatus for combining and splitting wavelength bands according to the fourth embodiment of the present invention as illustrated in Fig. 15.

[89] Fig. 20 illustrates a first alternative embodiment of an apparatus for combining and splitting wavelength bands according to the fifth embodiment of the present invention illustrated in Fig. 19.

[90] More specifically, an apparatus for combining and splitting wavelength bands according to the first alternative embodiment of the fifth embodiment as illustrated in Fig. 20 illustrates a case that the functions of the respective pass ports and the respective reflection ports of the first and the second CWDM filters are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 19 so that each pass port of the first and the second CWDM filters in Fig. 19 is changed to a reflection port in Fig. 20, while each reflection port of the first and the second CWDM filters in Fig. 19 is changed to a pass port in Fig. 20. In this case, each of the first and the second CWDM filters outputs a signal having a wavelength band (Z-band) with the range of 1260 ~ 1280 nm and/or the range of 1300 ~ 1320 nm through the pass port, while outputting a signal having a remaining wavelength band except Z-band through the reflection port.

[91] Fig. 21 illustrates a second alternative embodiment of an apparatus for combining and splitting wavelength bands according to the fifth embodiment of the present invention illustrated in Fig. 19.

[92] More specifically, an apparatus for combining and splitting wavelength bands according to the second alternative embodiment of the fifth embodiment as illustrated in Fig. 21 illustrates a case that the functions of the pass port and the reflection port of the edge filter are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 19 so that the pass port of the edge filter in Fig. 19 is changed to a reflection port in Fig. 21, while the reflection port of the edge filter in Fig. 19 is changed to a pass port in Fig. 21. In this case, the edge filter has a function of splitting a signal having a wavelength band (X-band) with 1360 nm or less from a signal inputted into the common port through the pass port, while having a function of splitting a signal having a wavelength band (Y-band) with 1415 nm or more therefrom through the reflection port.

[93] Fig. 22 illustrates a third alternative embodiment of an apparatus for combining and splitting wavelength bands according to the fifth embodiment of the present invention illustrated in Fig. 19.

[94] More specifically, an apparatus for combining and splitting wavelength bands according to the third alternative embodiment of the fifth embodiment as illustrated in Fig. 22 illustrates a case that the functions of the respective pass ports and the respective reflection ports of the first and the second CWDM filters and the edge filter are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 19 so that each pass port of the first and the second CWDM filters and the edge filter in Fig. 19 is changed to a reflection port in Fig. 22, while each reflection port of the first and the second CWDM filters and the edge filter in Fig. 19 is changed to a pass port in Fig. 22. In this case, each of the first and the second CWDM filters outputs a signal having a wavelength band (Z-band) with the range of 1260 ~ 1280 nm and/or the range of 1300 - 1320 nm through the pass port, while outputting a signal having a remaining wavelength band except Z-band through the reflection port. In addition, the edge filter has a function of splitting a signal having a wavelength band (X-band) with 1360 nm or less from a signal inputted into the common port through the pass port, while having a function of splitting a signal having a wavelength band (Y-band) with 1415 nm or more therefrom through the reflection port.

[95] In the meanwhile, a filter for passing Y-band may be added between the first

CWDM filter and the edge filter in Figs. 19 to 22, in order to reduce crosstalk of Xl -band and X2-band which influences Y-band and Z-band. In this case, the filter for passing Y-band may be embodied by an edge filter or a band-pass filter (BPF).

[96] Fig. 23 illustrates a sixth embodiment of an apparatus for combining and splitting wavelength bands for bi-directional transmission according to the present invention illustrated in Fig. 2.

[97] Referring to Fig. 23, an apparatus for combining and splitting wavelength bands according to a sixth embodiment of the present invention comprises a first CWDM filter for splitting Z-bands having a range of 1260 ~ 1280 nm and a range of 1300 ~ 1320 nm within X-band having 1360 nm or less from a wavelength band of light being transmitted; a second CWDM filter for splitting Z-bands having the range of 1260 ~ 1280 nm and/or the range of 1300 ~ 1320 nm within X-band having 1360 nm or less from the wavelength band of light being transmitted; and an edge filter for splitting X- band having 1360 nm or less and Y-band having 1415 nm or more within the wavelength band of light being transmitted. In this sixth embodiment, a reflection port of the first CWDM filter is connected to a reflection port of the edge filter, while a pass port of the first CWDM filter is connected to a pass port of the second CWDM filter. In addition, a reflection port of the second CWDM filter is connected to a common port of the edge filter. Referring to Fig. 23, it is fully understood that an apparatus for combining and splitting wavelength bands according to the sixth embodiment of the present invention performs the same function as an apparatus for combining and splitting wavelength bands according to the fourth and the fifth embodiments of the present invention as illustrated in Figs. 15 and 19, although the characteristic of the pass ports and the reflection ports in Fig. 23 has a reversed characteristic of the pass ports and the reflection ports in Figs. 15 and 19.

[98] Fig. 24 illustrates a first alternative embodiment of an apparatus for combining and splitting wavelength bands according to the sixth embodiment of the present invention illustrated in Fig. 23.

[99] More specifically, an apparatus for combining and splitting wavelength bands according to the first alternative embodiment of the sixth embodiment as illustrated in Fig. 24 illustrates a case that the functions of the respective pass ports and the respective reflection ports of the first and the second CWDM filters are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 23 so that each pass port of the first and the second CWDM filters in Fig. 23 is changed to a reflection port in Fig. 24, while each reflection port of the first and the second CWDM filters in Fig. 23 is changed to a pass port in Fig. 24. In this case, each of the first and the second CWDM filters has a function of splitting a signal having a wavelength band (Z-band) with the range of 1260 ~ 1280 nm and/or the range of 1300 ~ 1320 nm from a signal inputted into the common port through the reflection port, while having a function of splitting a signal having a remaining wavelength band except Z-band through the pass port.

[100] Fig. 25 illustrates a second alternative embodiment of an apparatus for combining and splitting wavelength bands according to the sixth embodiment of the present invention illustrated in Fig. 23.

[101] More specifically, an apparatus for combining and splitting wavelength bands according to the second alternative embodiment of the sixth embodiment as illustrated in Fig. 25 illustrates a case that the functions of the pass port and the reflection port of the edge filter are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 23 so that the pass port of the edge filter in Fig. 23 is changed to a reflection port in Fig. 25, while the reflection port of the edge filter in Fig. 23 is changed to a pass port in Fig. 25. In this case, the edge filter outputs a signal having a wavelength band (X-band) with 1360 nm or less through the reflection port, while outputting a signal having a wavelength band (Y-band) with 1415 nm or more through the pass port.

[102] Fig. 26 illustrates a third alternative embodiment of an apparatus for combining and splitting wavelength bands according to the sixth embodiment of the present invention illustrated in Fig. 23.

[103] More specifically, an apparatus for combining and splitting wavelength bands according to the third alternative embodiment of the sixth embodiment as illustrated in Fig. 26 illustrates a case that the functions of the respective pass ports and the respective reflection ports of the first and the second CWDM filters and the edge filter are switched each other in an apparatus for combining and splitting wavelength bands illustrated in Fig. 23 so that each pass port of the first and the second CWDM filters and the edge filter in Fig. 23 is changed to a reflection port in Fig. 26, while each reflection port of the first and the second CWDM filters and the edge filter in Fig. 23 is changed to a pass port in Fig. 26. In this case, each of the first and the second CWDM filters has a function of splitting a signal having a wavelength band (Z-band) with the range of 1260 ~ 1280 nm and/or the range of 1300 ~ 1320 nm from a signal inputted into the common port through the reflection port, while having a function of splitting a signal having a remaining wavelength band except Z-band through the pass port. In addition, the edge filter outputs a signal having a wavelength band (X-band) with 1360 nm or less through the reflection port, while outputting a signal having a wavelength band (Y-band) with 1415 nm or more through the pass port.

[104] In the meanwhile, a filter for passing Y-band may be added between the first

CWDM filter and the edge filter in Figs. 23 to 26, in order to reduce crosstalk of Xl -band and X2-band which influences Y-band and Z-band. In this case, the filter for passing Y-band may be embodied by an edge filter or a band-pass filter (BPF).

[105] Although it is illustrated and described, in the first to sixth embodiment and their respective alternative embodiments as illustrated in Figs. 3 to 26, that an apparatus for combining and splitting wavelength bands having three ports according to the present invention is comprised of a combination of three WDM filters (either two edge filters and one CWDM filter, or one edge filter and two CWDM filters), any skilled person on the art may understand fully that an apparatus for combining and splitting wavelength bands having three ports according to the present invention can be embodied by any one integral device having the same function as the combination of three WDM filters described above. Such a one integral device has an advantage that it is capable of minimizing an insertion loss through the three input and output ports, when compared with the combination of three WDM filters. Further, the ranges of X- band, Y-band, and Z-band used in an apparatus for combining and splitting wavelength bands according to the present invention described above is illustrative, the scope of the present invention is not intended to be limited to the specific ranges of X-band, Y- band, and Z-band. For example, in case that an apparatus for combining and splitting wavelength bands according to the present invention is embodied by using wavelength-tunable WDM filters, each of which is capable of varying the ranges of X- band, Y-band, and Z-band depending on necessity. In addition, a CWDM filter used in an apparatus for combining and splitting wavelength bands according to the present invention described above may have a function of splitting one or more Z-bands (Zl -band, Z2-band, ... etc.) so that it may expand a wavelength band to be combined and split additionally. An apparatus for combining and splitting wavelength bands according to the present invention described above has a function of combining and splitting wavelength bands for new bi-directional transmission, while accommodating an existing wavelength band as it is, where the existing wavelength band is transmitted bi-directionally through a transmission path in a one-line. Accordingly, when applying apparatus for combining and splitting wavelength bands according to the present invention to an existing metro network or access network, it is possible to expand the existing metro network or access network for the purpose of upgrading. For example, when applying an apparatus for combining and splitting wavelength bands according to the present invention illustrated in Figs. 3 to 6 to a access network, it is possible to add Yl -band and Y2-band as bi-directional signal bands for a WDM-PON in bi-directional transmission signals of a TDM-PON where a wavelength band (X-band) with a range of 1260 - 1280 nm is used as an upstream signal, while a wavelength band (Zl-band) with a range of 1480 ~ 1500 nm is used as a downstream signal. Further, it is possible to add a wavelength band (Z2-band) with a range of 1550 ~ 1560 nm as wavelength band for a video overlay signal. More specifically, when connecting the common port of the first edge filter of an apparatus for combining and splitting wavelength bands according to the present invention illustrated in Figs. 3 to 6 to an optical line termination (OLT) at a central office (CO) of a TDM-PON, connecting the common port of the second edge filter thereof to a remote node (RN), and connecting the pass port of the CWDM filter thereof an OLT of a WDM-PON, an added apparatus for combining and splitting wavelength bands according to the present invention can perform a function of combining and splitting new signals for bi-directional transmission, while simultaneously performing a function of upgrading an existing access network (i.e., a function of providing a service with a higher bandwidth by adding a WDM-PON). Further, an apparatus for combining and splitting wavelength bands according to the present invention is possible to increase flexibility and expansibility of an existing network, because an OLT of a new network may be added at CO or at any positions of the new network, depending on the positions of an apparatus for combining and splitting wavelength bands according to the present invention to be added.

Industrial Applicability

[107] An apparatus for combining and splitting wavelength bands having three input and output ports according to the present invention has the following advantages:

[108] 1. The present invention can be embodied at low costs and with a simple configuration so that it may function as the prior art add/drop multiplexers.

[109] 2. Unlike the prior art add/drop multiplexers which can combine and split only a signal with a specific wavelength, the present invention may combine a wavelength band having a certain range with or splitting it from an existing signal band so that high usability thereof can be accomplished in the present invention.

[110] 3. The present invention may be utilized as a device for upgrading and expanding an existing metro network or an existing access network so that performance of an optical communications system can be enhanced at low costs.

[I l l] 4. The present invention may increase flexibility and expansibility of an existing metro network or an existing access network.

[112] As various modifications could be made in the constructions and method herein described and illustrated without departing from the scope of the present invention, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above- described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.

Claims

[1] An apparatus for combining and splitting wavelength bands having three input and output ports for bi-directional transmission comprising: two wavelength division multiplexing (WDM) filters, each of which splits X- band having a range of a first wavelength or less and Y-band having a range of a second wavelength or more from a wavelength band of light being transmitted though the three input and output ports; and one WDM filter for splitting one or more Z-bands having a range of a third wavelength within either X-band having the range of the first wavelength or less or Y-band having the range of the second wavelength or more.

[2] The apparatus for combining and splitting wavelength bands of claim 1, wherein any two of the three input and output ports are respectively comprised of a first edge filter for splitting X-band having the range of the first wavelength or less and Y-band having the range of the second wavelength or more from the wavelength band of light being transmitted; and a second edge filter for splitting X-band having the range of the first wavelength or less and Y-band having the range of the second wavelength or more from the wavelength band of light being transmitted, and wherein one remaining input and output port is comprised of a coarse wavelength division multiplexing (CWDM) filter for splitting one or more Z- bands having the range of the third wavelength within Y-band having the range of the second wavelength or more.

[3] The apparatus for combining and splitting wavelength bands of claim 2, wherein the first edge filter has a first common port, a first reflection port, and a first pass port, wherein the second edge filter has a second common port, a second reflection port, and a second pass port, wherein the CWDM filter has a third common port, a third reflection port, and a third pass port, wherein the first reflection port of the first edge filter is connected to the third reflection port of the CWDM filter, wherein the first pass port of the first edge filter is connected to the second pass port of the second edge filter, wherein the second reflection port of the second edge filter is connected to the third common port of the CWDM filter, wherein the first edge filter outputs an X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the first common port, through the first pass port, while outputting a Y-band signal having the range of the second wavelength or more therefrom through the first reflection port, wherein the second edge filter outputs the X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the second common port, through the second pass port, while outputting the Y-band signal having the range of the second wavelength or more therefrom through the second reflection port, and wherein the CWDM filter outputs one or more Z-band signals having the range of the third wavelength through the third reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the third pass port.

[4] The apparatus for combining and splitting wavelength bands of claim 2, wherein the first edge filter has a first common port, a first reflection port, and a first pass port, wherein the second edge filter has a second common port, a second reflection port, and a second pass port, wherein the CWDM filter has a third common port, a third reflection port, and a third pass port, wherein the first reflection port of the first edge filter is connected to the third pass port of the CWDM filter, wherein the first pass port of the first edge filter is connected to the second pass port of the second edge filter, wherein the second reflection port of the second edge filter is connected to the third common port of the CWDM filter, wherein the first edge filter outputs an X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the first common port, through the first pass port, while outputting a

Y-band signal having the range of the second wavelength or more therefrom through the first reflection port, wherein the second edge filter outputs the X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the second common port, through the second pass port, while outputting the Y-band signal having the range of the second wavelength or more therefrom through the second reflection port, and wherein the CWDM filter outputs one or more Z-band signals having the range of the third wavelength through the third pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the third reflection port.

[5] The apparatus for combining and splitting wavelength bands of claim 2, wherein the first edge filter has a first common port, a first reflection port, and a first pass port, wherein the second edge filter has a second common port, a second reflection port, and a second pass port, wherein the CWDM filter has a third common port, a third reflection port, and a third pass port, wherein the first pass port of the first edge filter is connected to the third reflection port of the CWDM filter, wherein the first reflection port of the first edge filter is connected to the second reflection port of the second edge filter, wherein the second pass port of the second edge filter is connected to the third common port of the CWDM filter, wherein the first edge filter outputs an X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the first common port, through the first reflection port, while outputting a Y-band signal having the range of the second wavelength or more therefrom through the first pass port, wherein the second edge filter outputs the X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the second common port, through the second reflection port, while outputting the Y-band signal having the range of the second wavelength or more therefrom through the second pass port, and wherein the CWDM filter outputs one or more Z-band signals having the range of the third wavelength through the third reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the third pass port.

[6] The apparatus for combining and splitting wavelength bands of claim 2, wherein the first edge filter has a first common port, a first reflection port, and a first pass port, wherein the second edge filter has a second common port, a second reflection port, and a second pass port, wherein the CWDM filter has a third common port, a third reflection port, and a third pass port, wherein the first pass port of the first edge filter is connected to the third pass port of the CWDM filter, wherein the first reflection port of the first edge filter is connected to the second reflection port of the second edge filter, wherein the second pass port of the second edge filter is connected to the third common port of the CWDM filter, wherein the first edge filter outputs an X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the first common port, through the first reflection port, while outputting a Y-band signal having the range of the second wavelength or more therefrom through the first pass port, wherein the second edge filter outputs the X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the second common port, through the second reflection port, while outputting the Y-band signal having the range of the second wavelength or more therefrom through the second pass port, and wherein the CWDM filter outputs one or more Z-band signals having the range of the third wavelength through the third pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the third reflection port.

[7] The apparatus for combining and splitting wavelength bands of claim 1, wherein two of the three input and output ports are respectively comprised of a first edge filter for splitting X-band having the range of the first wavelength or less and Y-band having the range of the second wavelength or more from the wavelength band of light being transmitted; and a second edge filter for splitting X-band having the range of the first wavelength or less and Y-band having the range of the second wavelength or more from the wavelength band of light being transmitted, and wherein one remaining input and output port is comprised of a coarse wavelength division multiplexing (CWDM) filter for splitting one or more Z- bands having the range of the third wavelength within either X-band having the range of the first wavelength or less.

[8] The apparatus for combining and splitting wavelength bands of claim 7, wherein the first edge filter has a first common port, a first reflection port, and a first pass port, wherein the second edge filter has a second common port, a second reflection port, and a second pass port, wherein the CWDM filter has a third common port, a third reflection port, and a third pass port, wherein the first reflection port of the first edge filter is connected to the third reflection port of the CWDM filter, wherein the first pass port of the first edge filter is connected to the second pass port of the second edge filter, wherein the second reflection port of the second edge filter is connected to the third common port of the CWDM filter, wherein the first edge filter outputs an X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the first common port, through the first reflection port, while outputting a Y-band signal having the range of the second wavelength or more therefrom through the first pass port, wherein the second edge filter outputs the X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the second common port, through the second reflection port, while outputting the Y-band signal having the range of the second wavelength or more therefrom through the second pass port, and wherein the CWDM filter outputs one or more Z-band signals having the range of the third wavelength through the third reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the third pass port.

[9] The apparatus for combining and splitting wavelength bands of claim 7, wherein the first edge filter has a first common port, a first reflection port, and a first pass port, wherein the second edge filter has a second common port, a second reflection port, and a second pass port, wherein the CWDM filter has a third common port, a third reflection port, and a third pass port, wherein the first reflection port of the first edge filter is connected to the third pass port of the CWDM filter, wherein the first pass port of the first edge filter is connected to the second pass port of the second edge filter, wherein the second reflection port of the second edge filter is connected to the third common port of the CWDM filter, wherein the first edge filter outputs an X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the first common port, through the first reflection port, while outputting a Y-band signal having the range of the second wavelength or more therefrom through the first pass port, wherein the second edge filter outputs the X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the second common port, through the second reflection port, while outputting the Y-band signal having the range of the second wavelength or more therefrom through the second pass port, and wherein the CWDM filter outputs one or more Z-band signals having the range of the third wavelength through the third pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the third reflection port.

[10] The apparatus for combining and splitting wavelength bands of claim 7, wherein the first edge filter has a first common port, a first reflection port, and a first pass port, wherein the second edge filter has a second common port, a second reflection port, and a second pass port, wherein the CWDM filter has a third common port, a third reflection port, and a third pass port, wherein the first pass port of the first edge filter is connected to the third reflection port of the CWDM filter, wherein the first reflection port of the first edge filter is connected to the second reflection port of the second edge filter, wherein the second pass port of the second edge filter is connected to the third common port of the CWDM filter, wherein the first edge filter outputs an X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the first common port, through the first pass port, while outputting a

Y-band signal having the range of the second wavelength or more therefrom through the first reflection port, wherein the second edge filter outputs the X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the second common port, through the second pass port, while outputting the Y-band signal having the range of the second wavelength or more therefrom through the second reflection port, and wherein the CWDM filter outputs one or more Z-band signals having the range of the third wavelength through the third reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the third pass port.

[11] The apparatus for combining and splitting wavelength bands of claim 7, wherein the first edge filter has a first common port, a first reflection port, and a first pass port, wherein the second edge filter has a second common port, a second reflection port, and a second pass port, wherein the CWDM filter has a third common port, a third reflection port, and a third pass port, wherein the first pass port of the first edge filter is connected to the third pass port of the CWDM filter, wherein the first reflection port of the first edge filter is connected to the second reflection port of the second edge filter, wherein the second pass port of the second edge filter is connected to the third common port of the CWDM filter, wherein the first edge filter outputs an X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the first common port, through the first pass port, while outputting a

[12] The apparatus for combining and splitting wavelength bands of any one of claims 2 to 6, wherein the apparatus for combining and splitting wavelength bands further comprises a filter for passing Z-band between the first edge filter and the CWDM filter, in order to reduce crosstalk of Y-band which influences X-band and Z- band.

[13] The apparatus for combining and splitting wavelength bands of any one of claims 7 to 11 , wherein the apparatus for combining and splitting wavelength bands further comprises a filter for passing Z-band between the first edge filter and the CWDM filter, in order to reduce crosstalk of X-band which influences Y-band and Z- band.

[14] The apparatus for combining and splitting wavelength bands of claim 12, wherein the filter for passing Z-band is embodied by a separate CWDM filter or a separate band-pass filter (BPF).

[15] The apparatus for combining and splitting wavelength bands of claim 13, wherein the filter for passing Z-band is embodied by a separate CWDM filter or a separate band-pass filter (BPF).

[16] The apparatus for combining and splitting wavelength bands of any one of claims 1 to 6, wherein Y-band is either Yl -band or Y2-band, and wherein Yl -band and Y2-band are respectively selected from anyone consisting a group of E-band, S-band, C-band, and L-band.

[17] The apparatus for combining and splitting wavelength bands of any one of claims 1 to 6, wherein the first wavelength is 1360 nm, wherein the second wavelength is 1415 nm, and wherein the third wavelength is either one or both of 1480 ~ 1500 nm and 1550 ~

1560 nm.

[18] The apparatus for combining and splitting wavelength bands of any one of claim

1 and claims 7 to 11 , wherein X-band is either one of X l-band and X2-band, and wherein X l-band and X2-band are respectively a certain part within a wavelength of O-band.

[19] The apparatus for combining and splitting wavelength bands of any one of claims 1 and 7 to 11 , wherein the first wavelength is 1360 nm, wherein the second wavelength is 1415 nm, and wherein the third wavelength is either one or both of 1260 ~ 1280 nm and 1300 ~

1320 nm. [20] The apparatus for combining and splitting wavelength bands of any one of claims 1, 2 and 7, wherein the three input and output ports is embodied by any one integral device capable of minimizing an insertion loss through the three input and output ports.

[21] The apparatus for combining and splitting wavelength bands of claim 1, wherein the WDM filters are respectively embodied by a wavelength-tunable

WDM filter capable of varying the ranges of X-band, Y-band, and Z-band.

[22] An apparatus for combining and splitting wavelength bands having three input and output ports for bi-directional transmission comprising: one wavelength division multiplexing (WDM) filter for splitting X-band having a range of a first wavelength or less and Y-band having a range of a second wavelength or more from a wavelength band of light being transmitted though the three input and output ports; and two WDM filters, each of which splits one or more Z-bands having a range of a third wavelength within either X-band having the range of the first wavelength or less or Y-band having the range of the second wavelength or more.

[23] The apparatus for combining and splitting wavelength bands of claim 22, wherein any one of the three input and output ports is comprised of an edge filter for splitting X-band having the range of the first wavelength or less and Y-band having the range of the second wavelength or more from the wavelength band of light being transmitted, and wherein two remaining input and output ports are respectively comprised of a first coarse wavelength division multiplexing (CWDM) filter for splitting one or more Z-bands having the range of the third wavelength within Y-band having the range of the second wavelength or more; and a second CWDM filter for splitting one or more Z-bands having the range of the third wavelength within Y-band having the range of the second wavelength or more.

[24] The apparatus for combining and splitting wavelength bands of claim 23, wherein the first CWDM filter has a first common port, a first reflection port, and a first pass port, wherein the second CWDM filter has a second common port, a second reflection port, and a second pass port, wherein the edge filter has a third common port, a third reflection port, and a third pass port, wherein the first reflection port of the first CWDM filter is connected to the second reflection port of the second CWDM filter, wherein the first pass port of the first CWDM filter is connected to the third pass port of the edge filter, wherein the third reflection port of the edge filter is connected to the second common port of the second CWDM filter, wherein the first CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the first common port, through the first reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the first pass port, wherein the second CWDM filter outputs one or more Z-band signals having the range of the third wavelength through the second reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the second pass port, and wherein the edge filter outputs an X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the third common port, through the third pass port, while outputting a Y-band signal having the range of the second wavelength or more therefrom through the third reflection port.

[25] The apparatus for combining and splitting wavelength bands of claim 23, wherein the first CWDM filter has a first common port, a first reflection port, and a first pass port, wherein the second CWDM filter has a second common port, a second reflection port, and a second pass port, wherein the edge filter has a third common port, a third reflection port, and a third pass port, wherein the first pass port of the first CWDM filter is connected to the second pass port of the second CWDM filter, wherein the first reflection port of the first CWDM filter is connected to the third pass port of the edge filter, wherein the third reflection port of the edge filter is connected to the second common port of the second CWDM filter, wherein the first CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the first common port, through the first pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the first reflection port, wherein the second CWDM filter outputs one or more Z-band signals having the range of the third wavelength through the second pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the second reflection port, and wherein the edge filter outputs an X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the third common port, through the third pass port, while outputting a Y-band signal having the range of the second wavelength or more therefrom through the third reflection port.

[26] The apparatus for combining and splitting wavelength bands of claim 23, wherein the first CWDM filter has a first common port, a first reflection port, and a first pass port, wherein the second CWDM filter has a second common port, a second reflection port, and a second pass port, wherein the edge filter has a third common port, a third reflection port, and a third pass port, wherein the first reflection port of the first CWDM filter is connected to the second reflection port of the second CWDM filter, wherein the first pass port of the first CWDM filter is connected to the third reflection port of the edge filter, wherein the third pass port of the edge filter is connected to the second common port of the second CWDM filter, wherein the first CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the first common port, through the first reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the first pass port, wherein the second CWDM filter outputs one or more Z-band signals having the range of the third wavelength through the second reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the second pass port, and wherein the edge filter outputs an X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the third common port, through the third reflection port, while outputting a Y-band signal having the range of the second wavelength or more therefrom through the third pass port.

[27] The apparatus for combining and splitting wavelength bands of claim 23, wherein the first CWDM filter has a first common port, a first reflection port, and a first pass port, wherein the second CWDM filter has a second common port, a second reflection port, and a second pass port, wherein the edge filter has a third common port, a third reflection port, and a third pass port, wherein the first pass port of the first CWDM filter is connected to the second pass port of the second CWDM filter, wherein the first reflection port of the first CWDM filter is connected to the third reflection port of the edge filter, wherein the third pass port of the edge filter is connected to the second common port of the second CWDM filter, wherein the first CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the first common port, through the first pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the first reflection port, wherein the second CWDM filter outputs one or more Z-band signals having the range of the third wavelength through the second pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the second reflection port, and wherein the edge filter outputs an X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the third common port, through the third reflection port, while outputting a Y-band signal having the range of the second wavelength or more therefrom through the third pass port.

[28] The apparatus for combining and splitting wavelength bands of claim 23, wherein the first CWDM filter has a first common port, a first reflection port, and a first pass port, wherein the second CWDM filter has a second common port, a second reflection port, and a second pass port, wherein the edge filter has a third common port, a third reflection port, and a third pass port, wherein the first reflection port of the first CWDM filter is connected to the third reflection port of the edge filter, wherein the first pass port of the first CWDM filter is connected to the second pass port of the second CWDM filter, wherein the second reflection port of the second CWDM filter is connected to the third common port of the edge filter, wherein the first CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the first common port, through the first pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the first reflection port, wherein the second CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the second common port, through the second pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the second reflection port, and wherein the edge filter outputs an X-band signal having the range of the first wavelength or less through the third reflection port, while outputting a Y-band signal having the range of the second wavelength or more through the third pass port.

[29] The apparatus for combining and splitting wavelength bands of claim 23, wherein the first CWDM filter has a first common port, a first reflection port, and a first pass port, wherein the second CWDM filter has a second common port, a second reflection port, and a second pass port, wherein the edge filter has a third common port, a third reflection port, and a third pass port, wherein the first pass port of the first CWDM filter is connected to the third reflection port of the edge filter, wherein the first reflection port of the first CWDM filter is connected to the second reflection port of the second CWDM filter, wherein the second pass port of the second CWDM filter is connected to the third common port of the edge filter, wherein the first CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the first common port, through the first reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the first pass port, wherein the second CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the second common port, through the second reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the second pass port, and wherein the edge filter outputs an X-band signal having the range of the first wavelength or less through the third reflection port, while outputting a Y-band signal having the range of the second wavelength or more through the third pass port.

[30] The apparatus for combining and splitting wavelength bands of claim 23, wherein the first CWDM filter has a first common port, a first reflection port, and a first pass port, wherein the second CWDM filter has a second common port, a second reflection port, and a second pass port, wherein the edge filter has a third common port, a third reflection port, and a third pass port, wherein the first reflection port of the first CWDM filter is connected to the third pass port of the edge filter, wherein the first pass port of the first CWDM filter is connected to the second pass port of the second CWDM filter, wherein the second reflection port of the second CWDM filter is connected to the third common port of the edge filter, wherein the first CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the first common port, through the first pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the first reflection port, wherein the second CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the second common port, through the second pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the second reflection port, and wherein the edge filter outputs an X-band signal having the range of the first wavelength or less through the third pass port, while outputting a Y-band signal having the range of the second wavelength or more through the third reflection port.

[31] The apparatus for combining and splitting wavelength bands of claim 23, wherein the first CWDM filter has a first common port, a first reflection port, and a first pass port, wherein the second CWDM filter has a second common port, a second reflection port, and a second pass port, wherein the edge filter has a third common port, a third reflection port, and a third pass port, wherein the first pass port of the first CWDM filter is connected to the third pass port of the edge filter, wherein the first reflection port of the first CWDM filter is connected to the second reflection port of the second CWDM filter, wherein the second pass port of the second CWDM filter is connected to the third common port of the edge filter, wherein the first CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the first common port, through the first reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the first pass port, wherein the second CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the second common port, through the second reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the second pass port, and wherein the edge filter outputs an X-band signal having the range of the first wavelength or less through the third pass port, while outputting a Y-band signal having the range of the second wavelength or more through the third reflection port.

[32] The apparatus for combining and splitting wavelength bands of any one of claims 23 to 31, wherein the apparatus for combining and splitting wavelength bands further comprises a filter for passing X-band between the first CWDM filter and the edge filter, in order to reduce crosstalk of Y-band which influences X-band and

Z-band.

[33] The apparatus for combining and splitting wavelength bands of claim 32, wherein the filter for passing X-band is embodied by a separate edge filter or a separate band-pass filter (BPF).

[34] The apparatus for combining and splitting wavelength bands of any one of claims 22 to 31, wherein Y-band is either Yl -band or Y2-band, and wherein Yl -band and Y2-band are respectively selected from anyone consisting a group of E-band, S-band, C-band, and L-band.

[35] The apparatus for combining and splitting wavelength bands of any one of claims 22 to 31, wherein the first wavelength is 1360 nm, wherein the second wavelength is 1415 nm, and wherein the third wavelength is either one or both of 1480 ~ 1500 nm and 1550 ~

1560 nm.

[36] The apparatus for combining and splitting wavelength bands of claim 22, wherein any one of the three input and output ports is comprised of an edge filter for splitting X-band having the range of the first wavelength or less and Y-band having the range of the second wavelength or more from the wavelength band of light being transmitted, and wherein two remaining input and output ports are respectively comprised of a first coarse wavelength division multiplexing (CWDM) filter for splitting one or more Z-bands having the range of the third wavelength within X-band having the range of the first wavelength or less; and a second CWDM filter for splitting one or more Z-bands having the range of the third wavelength within X-band having the range of the first wavelength or less.

[37] The apparatus for combining and splitting wavelength bands of claim 36, wherein the first CWDM filter has a first common port, a first reflection port, and a first pass port, wherein the second CWDM filter has a second common port, a second reflection port, and a second pass port, wherein the edge filter has a third common port, a third reflection port, and a third pass port, wherein the first reflection port of the first CWDM filter is connected to the second reflection port of the second CWDM filter, wherein the first pass port of the first CWDM filter is connected to the third pass port of the edge filter, wherein the third reflection port of the edge filter is connected to the second common port of the second CWDM filter, wherein the first CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the first common port, through the first reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the first pass port, wherein the second CWDM filter outputs one or more Z-band signals having the range of the third wavelength through the second reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the second pass port, and wherein the edge filter outputs an X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the third common port, through the third reflection port, while outputting a Y-band signal having the range of the second wavelength or more therefrom through the third pass port.

[38] The apparatus for combining and splitting wavelength bands of claim 36, wherein the first CWDM filter has a first common port, a first reflection port, and a first pass port, wherein the second CWDM filter has a second common port, a second reflection port, and a second pass port, wherein the edge filter has a third common port, a third reflection port, and a third pass port, wherein the first pass port of the first CWDM filter is connected to the second pass port of the second CWDM filter, wherein the first reflection port of the first CWDM filter is connected to the third pass port of the edge filter, wherein the third reflection port of the edge filter is connected to the second common port of the second CWDM filter, wherein the first CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the first common port, through the first pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the first reflection port, wherein the second CWDM filter outputs one or more Z-band signals having the range of the third wavelength through the second pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the second reflection port, and wherein the edge filter outputs an X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the third common port, through the third reflection port, while outputting a Y-band signal having the range of the second wavelength or more therefrom through the third pass port.

[39] The apparatus for combining and splitting wavelength bands of claim 36, wherein the first CWDM filter has a first common port, a first reflection port, and a first pass port, wherein the second CWDM filter has a second common port, a second reflection port, and a second pass port, wherein the edge filter has a third common port, a third reflection port, and a third pass port, wherein the first reflection port of the first CWDM filter is connected to the second reflection port of the second CWDM filter, wherein the first pass port of the first CWDM filter is connected to the third reflection port of the edge filter, wherein the third pass port of the edge filter is connected to the second common port of the second CWDM filter, wherein the first CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the first common port, through the first reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the first pass port, wherein the second CWDM filter outputs one or more Z-band signals having the range of the third wavelength through the second reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the second pass port, and wherein the edge filter outputs an X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the third common port, through the third pass port, while outputting a Y-band signal having the range of the second wavelength or more therefrom through the third reflection port.

[40] The apparatus for combining and splitting wavelength bands of claim 36, wherein the first CWDM filter has a first common port, a first reflection port, and a first pass port, wherein the second CWDM filter has a second common port, a second reflection port, and a second pass port, wherein the edge filter has a third common port, a third reflection port, and a third pass port, wherein the first pass port of the first CWDM filter is connected to the second pass port of the second CWDM filter, wherein the first reflection port of the first CWDM filter is connected to the third reflection port of the edge filter, wherein the third pass port of the edge filter is connected to the second common port of the second CWDM filter, wherein the first CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the first common port, through the first pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the first reflection port, wherein the second CWDM filter outputs one or more Z-band signals having the range of the third wavelength through the second pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the second reflection port, and wherein the edge filter outputs an X-band signal having the range of the first wavelength or less from the wavelength band of light being transmitted, which is inputted into the third common port, through the third pass port, while outputting a Y-band signal having the range of the second wavelength or more therefrom through the third reflection port.

[41] The apparatus for combining and splitting wavelength bands of claim 36, wherein the first CWDM filter has a first common port, a first reflection port, and a first pass port, wherein the second CWDM filter has a second common port, a second reflection port, and a second pass port, wherein the edge filter has a third common port, a third reflection port, and a third pass port, wherein the first reflection port of the first CWDM filter is connected to the third reflection port of the edge filter, wherein the first pass port of the first CWDM filter is connected to the second pass port of the second CWDM filter, wherein the second reflection port of the second CWDM filter is connected to the third common port of the edge filter, wherein the first CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the first common port, through the first pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the first reflection port, wherein the second CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the second common port, through the second pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the second reflection port, and wherein the edge filter outputs an X-band signal having the range of the first wavelength or less through the third pass port, while outputting a Y-band signal having the range of the second wavelength or more through the third reflection port.

[42] The apparatus for combining and splitting wavelength bands of claim 36, wherein the first CWDM filter has a first common port, a first reflection port, and a first pass port, wherein the second CWDM filter has a second common port, a second reflection port, and a second pass port, wherein the edge filter has a third common port, a third reflection port, and a third pass port, wherein the first pass port of the first CWDM filter is connected to the third reflection port of the edge filter, wherein the first reflection port of the first CWDM filter is connected to the second reflection port of the second CWDM filter, wherein the second pass port of the second CWDM filter is connected to the third common port of the edge filter, wherein the first CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the first common port, through the first reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the first pass port, wherein the second CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the second common port, through the second reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the second pass port, and wherein the edge filter outputs an X-band signal having the range of the first wavelength or less through the third pass port, while outputting a Y-band signal having the range of the second wavelength or more through the third reflection port.

[43] The apparatus for combining and splitting wavelength bands of claim 36, wherein the first CWDM filter has a first common port, a first reflection port, and a first pass port, wherein the second CWDM filter has a second common port, a second reflection port, and a second pass port, wherein the edge filter has a third common port, a third reflection port, and a third pass port, wherein the first reflection port of the first CWDM filter is connected to the third pass port of the edge filter, wherein the first pass port of the first CWDM filter is connected to the second pass port of the second CWDM filter, wherein the second reflection port of the second CWDM filter is connected to the third common port of the edge filter, wherein the first CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the first common port, through the first pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the first reflection port, wherein the second CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the second common port, through the second pass port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the second reflection port, and wherein the edge filter outputs an X-band signal having the range of the first wavelength or less through the third reflection port, while outputting a Y-band signal having the range of the second wavelength or more through the third pass port.

[44] The apparatus for combining and splitting wavelength bands of claim 36, wherein the first CWDM filter has a first common port, a first reflection port, and a first pass port, wherein the second CWDM filter has a second common port, a second reflection port, and a second pass port, wherein the edge filter has a third common port, a third reflection port, and a third pass port, wherein the first pass port of the first CWDM filter is connected to the third pass port of the edge filter, wherein the first reflection port of the first CWDM filter is connected to the second reflection port of the second CWDM filter, wherein the second pass port of the second CWDM filter is connected to the third common port of the edge filter, wherein the first CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the first common port, through the first reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the first pass port, wherein the second CWDM filter outputs one or more Z-band signals having the range of the third wavelength from the wavelength band of light being transmitted, which is inputted into the second common port, through the second reflection port, while outputting a signal having a remaining wavelength band except the range of the third wavelength through the second pass port, and wherein the edge filter outputs an X-band signal having the range of the first wavelength or less through the third reflection port, while outputting a Y-band signal having the range of the second wavelength or more through the third pass port.

[45] The apparatus for combining and splitting wavelength bands of any one of claims 36 to 44, wherein the apparatus for combining and splitting wavelength bands further comprises a filter for passing Y-band between the first CWDM filter and the edge filter, in order to reduce crosstalk of X-band which influences Y-band and Z-band.

[46] The apparatus for combining and splitting wavelength bands of claim 45, wherein the filter for passing Y-band is embodied by a separate edge filter or a separate band-pass filter (BPF).

[47] The apparatus for combining and splitting wavelength bands of any one of claims 22 and 36 to 44, wherein X-band is either Xl -band or X2-band, and wherein Xl -band and X2-band are respectively a certain part within a wavelength of O-band.

[48] The apparatus for combining and splitting wavelength bands of any one of claims 22 and 36 to 44, wherein the first wavelength is 1360 nm, wherein the second wavelength is 1415 nm, and wherein the third wavelength is either one or both of 1260 ~ 1280 nm and 1300 ■

1320 nm. [49] The apparatus for combining and splitting wavelength bands of any one of claims 22, 23 and 36, wherein the three input and output ports is embodied by any one integral device capable of minimizing an insertion loss through the three input and output ports. [50] The apparatus for combining and splitting wavelength bands of claim 22, wherein the WDM filters are respectively embodied by a wavelength-tunable

WDM filter capable of varying the ranges of X-band, Y-band, and Z-band.