HK1131271B - Optical transmission system and optical repeater - Google Patents

Description

Optical transmission system and optical relay device

Technical Field

The present invention relates to an optical transmission system and an optical relay apparatus, and more particularly to a PON-type optical transmission system and an optical relay apparatus thereof.

Background

In optical networks such as FTTH and CATV, a pon (passive optical network) type optical transmission system is used in which an optical transmission line connected to a center is branched by a passive splitter and laid out in a plurality of subscriber houses. This light transmission system is also referred to as pds (passive doublstar).

In such an Optical transmission system, a splitter is connected to an Optical fiber led from an osu (Optical sub Unit) in a central Optical Line Termination (OLT) to a Subscriber side, and Optical Line terminations (ONU) of a plurality of subscribers are connected via the Optical fiber to an Optical transmission Line split into a plurality of Optical lines by the splitter.

The following structures are known: in a PON-type or PDS-type optical transmission system in which an OLT and a plurality of ONUs are connected to each other via an optical fiber and a splitter, an optical relay device is connected to an optical transmission path between the OLT and the splitter in order to set the optical transmission path to a long distance.

Patent document 1 below describes a system in which a MUX/DEMUX and an optical relay device are connected to a conventional optical transmission system to enable wavelength division multiplexing communication (WDM). This optical relay adopts a structure shown in fig. 15.

The wavelength conversion device 101 has first and second 3dB couplers 102 and 103 provided at input/output terminals on the OLT side and the ONU side, respectively, and a light receiving element 104, a receiving circuit 105, a driving circuit 106, a light receiving element 107, and an isolator 108 are connected in this order in the signal transmission direction in a downstream signal system between the first 3dB coupler 102 and the second 3dB coupler 103, and a light receiving element 109, a receiving circuit 110, a driving circuit 111, a light emitting element 112, and an isolator 113 are connected in this order in the signal transmission direction in the upstream signal system.

In this device, optical signals output from the first and second 3dB couplers 102 and 103 to the light receiving elements 104 and 09 are converted into electrical signals by the light receiving elements 104 and 09, the electrical signals are subjected to 3R or 2R processing by the receiving circuits 105 and 110, and the electrical signals subjected to the 3R or 2R processing are further converted into optical signals by the driving circuits 106 and 107 and the light emitting elements 111 and 112 and output to the isolators 108 and 113. 3R is a function of equalizing amplification (reshaping), recognition reproduction (reproduction), and retiming (retiming), and 2R is a function of recognition reproduction and retiming.

Patent document 1: japanese patent laid-open publication No. 2002-261697

The optical relay device of CATV is generally placed outdoors far from the OLT, and it is necessary to manage the optical relay device in order to deal with such problems as a change in the output of the light emitting element due to a difference in the ambient temperature, failure to perform relay due to a power failure, transmission fluctuation abnormality of the power supply unit of the optical relay device, abnormality of the door opening of the housing, abnormality of the internal temperature rise, and abnormality of flooding.

In order to perform such management, there is a method of installing a management circuit in the optical relay apparatus and connecting the management circuit to an electrical communication line. However, since a new electric communication line for optical relay device management is laid, large-scale construction is required, thereby causing a problem of cost increase. In addition, in the case where there is no margin for laying a new electric communication line, it is necessary to abandon the management of the optical relay apparatus.

On the other hand, it is considered that optical multiplexing is performed using an optical signal having a wavelength dedicated to management of an optical relay device, unlike light having a wavelength generally used in an optical transmission system, but this system requires an optical wavelength multiplexing device, and therefore cannot be easily adopted from the viewpoints of cost, space margin, and the like.

Disclosure of Invention

An object of the present invention is to provide an optical relay apparatus and an optical transmission system in which a management function is easily introduced from the viewpoints of cost and operation.

In order to solve the above problem, a first aspect of the present invention is an optical relay apparatus provided in an optical transmission path between at least one subscriber-side optical line terminal apparatus having an ONU function and a center-side optical line terminal apparatus, the optical relay apparatus including: a first electric/optical conversion unit connected to a first optical transmission line of the center-side line termination device, and performing both optical-to-electric conversion and electrical-to-optical conversion; a second electrical/optical conversion unit connected to a second optical transmission line of the subscriber-side line termination device, and performing both optical-to-electrical conversion and electrical-to-optical conversion; and a transmission unit connected between the first electric/optical conversion unit and the second electric/optical conversion unit, and transmitting an optical relay device management signal to the optical transmission line.

A second aspect of the present invention is the optical relay device of the first aspect, wherein the transmission unit includes: an electric line connecting between the first electric/optical conversion unit and the second electric/optical conversion unit; and an ONU function unit which inputs and outputs an electric signal to and from the electric line via the electric signal connection unit.

A third aspect of the present invention is the optical relay device according to the second aspect, wherein the ONU function unit has a function identical to the ONU function used in the user-side device.

A fourth aspect of the present invention is the optical relay device of the second or third aspect, wherein the electric line includes: a first electric line that transmits the electric signal from the first electric/optical conversion unit to the second electric/optical conversion unit in a downstream direction; and a second electric line that transmits the electric signal from the second electric/optical conversion unit to the first electric/optical conversion unit in an upstream direction; the electric signal connecting part comprises: a first electrical signal connection part that branches the electrical signal transmitted in the first electrical line on the first electrical/optical conversion unit and the ONU functional part; and a second electrical signal connection part multiplexing an electrical signal output from the ONU-functional part into the electrical signal transmitted in the second electrical line.

A fifth aspect of the present invention is an optical relay apparatus provided in an optical transmission path between at least one customer premises-side optical line terminal apparatus and a center-side optical line terminal apparatus, the optical relay apparatus including: an optical signal processing unit interposed between a first optical transmission line on the center side and a second optical transmission line on the user house side in the optical transmission lines; an optical multiplexer/demultiplexer connected to the first or second optical transmission line; and a management optical line terminator that inputs/outputs a management electrical signal and is connected to the first or second optical transmission line via the optical multiplexer/demultiplexer.

A sixth aspect of the present invention is the optical repeater according to the fifth aspect, wherein the management optical line termination device has a function similar to that of an optical line termination device disposed on the customer premises side.

A seventh aspect of the present invention is the optical relay apparatus of the fifth or sixth aspect, wherein the management optical line termination apparatus is connected to one of the first optical transmission line and the second optical transmission line via the optical multiplexer/demultiplexer.

An eighth aspect of the present invention is an optical relay device according to any one of the fifth to seventh aspects, wherein the optical signal processing unit includes: a first electric/optical conversion unit connected to the first optical transmission line on the center side, and performing both of optical-to-electric conversion and electrical-to-optical conversion; a second electric/optical conversion unit connected to the second optical transmission line on the user side, and performing both of optical-to-electric conversion and electrical-to-optical conversion; and an electric line connected between the first electric/optical conversion unit and the second electric/optical conversion unit, transmitting an electric signal therebetween.

A ninth aspect of the present invention is the optical relay device according to any one of the fifth to eighth aspects, wherein at least one of the first electrical/optical conversion unit and the second electrical/optical conversion unit has a processing circuit for performing processing of equalization amplification, discrimination reproduction, and retiming.

A tenth aspect of the present invention is an optical transmission system including: an optical relay device according to one of the first to ninth aspects; a first optical line termination device in the center-side optical line termination device connected to the optical repeater device via the first optical transmission line; and a second optical line termination device in the subscriber premises-side optical line termination device connected to the optical repeater device via the second optical transmission line.

An eleventh aspect of the present invention is the optical transmission system of the tenth aspect, wherein the second optical transmission line is connected to the plurality of second optical line termination devices via an optical multiplexer/demultiplexer.

A twelfth aspect of the present invention is the optical transmission system of the tenth or eleventh aspect, wherein a plurality of the optical relay devices are connected via an optical transmission line.

Effects of the invention

According to the present invention, since the optical repeater has the first electrical/optical conversion unit connected to the first optical transmission line of the center-side line termination device and the second electrical/optical conversion unit connected to the second optical transmission line of the user-side line termination device, and the transmission unit for transmitting the management signal for the optical repeater is provided between the first and second electrical/optical conversion units, it is possible to manage the optical repeater without laying a new management line.

According to another aspect of the present invention, since the management function unit for transmitting the relay device management signal for managing the optical relay device is provided in the optical relay device and connected to the optical transmission line via the optical line terminal (ONU), it is not necessary to provide an electrical communication line for managing the optical relay device or to use an optical signal having a different wavelength from that of a normal optical transmission line, and the signal for managing the optical relay device can be transmitted to the center device without affecting the conventional operation.

Drawings

Fig. 1 is a structural diagram of an optical transmission system of a first embodiment of the present invention;

fig. 2 is a block diagram showing a configuration of an ONU functional unit used in an optical relay device of an optical transmission system according to a first embodiment of the present invention;

fig. 3 is a block diagram showing the configuration of an LSI used for the ONU functional section in the optical relay apparatus of the optical transmission system according to the first embodiment of the present invention;

fig. 4 is a block diagram showing a relationship with an ONU function as seen from the OLT in the optical transmission system according to the first embodiment of the present invention;

fig. 5 is a block diagram showing a configuration of an optical relay apparatus used in the optical transmission system according to the second embodiment of the present invention;

fig. 6 is a structural view of an optical transmission system according to a third embodiment of the present invention;

fig. 7 is a block diagram showing a relationship with an ONU function as seen from an OLT in an optical transmission system according to a third embodiment of the present invention;

fig. 8 is a structural view of an optical transmission system according to a fourth embodiment of the present invention;

fig. 9 is a block diagram showing a photoelectric conversion unit of an optical relay apparatus used in an optical transmission system according to a fourth embodiment of the present invention;

fig. 10 is a block diagram showing a configuration of a management ONU used in an optical relay apparatus of an optical transmission system according to a fourth embodiment of the present invention;

fig. 11 is a block diagram showing a relationship with an ONU function as seen from an OLT in an optical transmission system according to a fourth embodiment of the present invention;

fig. 12 is a block diagram showing a configuration of an optical relay apparatus used in an optical transmission system according to a fifth embodiment of the present invention;

fig. 13 is a block diagram showing a configuration of an optical transmission system according to a sixth embodiment of the present invention;

fig. 14 is a block diagram showing a relationship with an ONU function as seen from an OLT in an optical transmission system according to a sixth embodiment of the present invention;

fig. 15 is a side view showing an example of an optical relay apparatus used in a PON type optical transmission system according to the related art.

Description of the reference numerals

2. 3: optical fiber

4. 4-1, … 4-m: optical relay device

5: optical coupler

6-1, … 6-n: optical fiber

7—1，…7—n：ONU

21. 22: EO/OE moiety

23: electric circuit

24: electric signal connecting part

25: various devices

26: management function part

27: ONU function unit

63, 70: WDM coupler

64. 71: light receiving element

65. 72: receiving circuit

66. 68: driving circuit

67. 69: light emitting element

Detailed Description

(first embodiment)

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 1 is a configuration diagram of a PON type optical transmission system according to a first embodiment of the present invention.

In fig. 1, an optical transmission line such as CATV having optical fibers 2 and 3 connected to an Optical Line Terminal (OLT)1 on the center side is connected to an optical coupler 5 via an optical relay device 4. An optical transmission line branched into a plurality of paths by an optical coupler (optical multiplexer/demultiplexer) 5 is connected to optical line terminal units (ONU) 7-1, … 7-n (n is a natural number) of a plurality of customer premises via optical fibers 6-1, … 6-n. The ONUs 7-1 and … 7-n are each configured by an optical transceiver 8a and an ONU function 8b connected thereto.

Here, the term ONU generally includes the functions of the optical transceiver, but in describing the present invention, the ONU is described as being divided into two functions, that is, the optical transceiver and the ONU.

As the OLT1 and the ONUs 7-1 and … 7-n, for example, a predetermined device is selected which is applied to a GEPON (Gigabit Ethernet (registered trademark) PON) based on the EFM standard ieee802.3ah and a gpon (Gigabit Passive Optical network) based on the ITU-T recommendation g.984. x.

The optical relay apparatus 4 includes: a first EO/OE section (optical/electrical conversion unit) 21 connected to the optical fiber 2 on the OTL1 side; a second EO/OE section (optical/electrical conversion unit) 22 connected to the optical fiber 3 on the optical coupler 5 side; an electric line 23 that transmits electric signals between the first EO/OE section 21 and the second EO/OE section 22; an electrical signal connection portion 24 connected to the electrical line 23; various devices 25 such as a door switch sensor, a temperature sensor, a power supply voltage sensor, an alarm, and a heater, which are installed in the optical relay apparatus 4; a management function unit 26 for inputting/outputting detection signals, control setting signals, and the like to/from the first and second EO/OE units 21 and 22 and the various devices 25; an ONU functional unit 27 for inputting and outputting an electric signal is provided between the electric signal connecting unit 24 and the management functional unit 26.

The first EO/OE section 21 has the following structure: after electrically converting an optical signal transmitted in the downstream direction from the central OTL1 through the optical fiber 2, the optical signal is subjected to predetermined processing of 3R or 2R and output to the electric line 23, while an electric signal transmitted in the upstream direction from the second EO/OE unit 22 through the electric line 23 is converted into an optical signal and output to the optical fiber 2.

The second EO/OE unit 22 has a configuration in which an electrical signal transmitted in the downstream direction via the electric line 23 is converted into an optical signal and output to the optical fiber 3 at the customer premises side, and an optical signal transmitted in the upstream direction via the optical fiber 3 is electrically converted and then subjected to predetermined processing by 3R or 2R and output to the electric line 23.

The electrical signal connection portion 24 has the following structure: the electrical signals of the plural channels, which are transmitted in the downstream direction on the electric line 23 and subjected to TDM (time division multiplexing) according to the PON protocol, are split and transmitted to the first EO/OE unit 21 and the ONU functional unit 27, and the signals of the TDM channels, which are transmitted from the ONU functional unit 27 and subjected to the predetermined PON protocol, are multiplexed to the electrical signals in the upstream direction on the electric line 23 and transmitted on the electric line 23.

The management function unit 26 has the following circuit configuration: the status monitor signals of the first and second EO/OE sections 21, 22 and signals of the devices within the various devices 25 are input, and signals for controlling the respective devices or setting conditions within the first and second EO/OE sections 21, 22 and the various devices 25 are output.

The management function unit 26 has a CPU, a storage element, and the like, and is connected to the OTL1 by the ONU function unit 27 using a maintenance channel in the PON protocol. Alternatively, the LAN connection function of the ONU function unit 27 may be used to perform LAN connection with the OTL1 using the main signal channel in the PON protocol.

The ONU function unit 27 is a device having a function of connecting to the electric line 23 in the protocol standard of the PON interface, and has the following configuration: among the multiple channels transmitted in the downstream direction on the electric line 23, a signal of a predetermined channel corresponding to the ONU function unit 27 is extracted and subjected to data processing, and then transmitted to the management function unit 26, and a signal transmitted from the management function unit 26 is transmitted in the upstream direction on the electric line 23 in the predetermined channel. Specifically, the ONU function unit 27 has the configuration shown in fig. 2 except the optical transceiver 8a among the optical transceivers 8a and 8b constituting the ONUs 7-1 and … 7-n on the customer premises, and selects a channel different from the ONUs 7-1 and … 7-n.

In fig. 2, a first LAN interface 35 including a 10/100PHY controller 32, a transformer 33, and an RJ25 connector 34, a second LAN interface 39 including a 10/100/1000PHY controller 36, a transformer 37, and an RJ25 connector 38, a ZBT-RAM 40, and a data bus 41 are connected to a PON processing LSI31 having an input/output unit connected to the electrical signal connection unit 24. The data bus 41 is connected to an SRAM42 and a flash memory 43, and the flash memory 43 stores programs and the like. The RJ25 connector 38 is connected to the management function 26 via a plug.

As shown in fig. 3, the LSI31 has: a media access control (mac) interface 45 based on the ieee802.3ah standard connected to the electrical signal connection 24 via a Gigabit serial/parallel converter (Gigabit SerDes) 44; an epon (ethernet Passive optical network) search engine (look-up engine)46 connected to the MAC interface 45; 10/100MAC49 connected to EPON search engine 46 via switch 47 and ethernet (registered trademark) search engine 48; 10/100/1000MAC51 connected to EPON search engine 46 via switch 47 and gigabit ethernet search engine 50; a management interface 52 connected to the MAC interface 45; 80C51CPU53 connected to management interface 52; a GPIO interface 54; and I2C interface 55.

10/100MAC49 is connected to 10/100PHY controller 32, 10/100/1000MAC51 is connected to 10/100/1000PHY controller 36. The 80C51CPU53 is connected to the data bus 41 described above.

Further, the GPIO interface 54 may be connected to various devices 25 via the management function section 26 having the CPU function to collect device signals as relay device management signals for alarms and the like, but may also be directly connected to the GPIO interface 54 in accordance with the types and the number of signals of the various devices 25 to collect device signals as relay device management signals.

Similarly, the I2C interface 55 may be connected to various devices 25 via a management function unit 26 having a CPU function to collect device signals as relay device management signals such as alarms, or may be connected to various devices 25 via an analog-to-digital conversion port (not shown) having no CPU function to transmit temperature information as relay device management signals by connecting temperature sensors (not shown) to the various devices 25.

In fig. 1, reference numeral 59 denotes a supervisor (hypervisor) connected to the OTL1, and reference numeral 60 denotes a monitoring operation device which inputs and outputs signals to and from the supervisor 59 to monitor and operate the optical relay apparatus 4.

In the optical transmission system described above, optical signals in the upstream direction from the ONUs 7-1, … 7-n to the OLT1 are transmitted as follows.

Optical signals (burst signals) of a 1.3 μm wavelength band transmitted from the ONUs 7-1, … 7-n are combined by the optical coupler 5, and further transmitted to the second EO/OE unit 22 of the optical relay apparatus 4 via the optical fibers 6-1, … 6-n, 3.

In the optical relay apparatus 4, data indicating the operation states of the first and second EO/OE units 21 and 22 and detection data of the various devices 25 are detected by the management function unit 26, and further transmitted to the electrical signal connection unit 24 through the ONU function unit 27 on a predetermined channel.

The output signal from the ONU function portion 27 is multiplexed to a predetermined channel of the upstream electric signal transmitted on the electric line 23 via the electric signal connection portion 24, further converted into an optical signal by the first EO/OE portion 21, output to the optical fiber 2, and then received by the OTL 1. Among the optical signals received by the OTL1, an optical signal of a predetermined channel is stored as monitoring data of the optical relay apparatus 4 in the monitoring operation apparatus 60 via the management machine 59.

On the other hand, the optical signal in the downstream direction output from OLT1 is transmitted to ONUs 7-1, 7-n as follows.

The optical signal of the 1.49 μm wavelength band transmitted from the OLT1 is transmitted through the optical fiber 2 and input to the first EO/OE unit 21 of the optical relay apparatus 4. Among the optical signals, the optical relay monitoring control setting signal output from the monitoring operation device 60 to the management machine 59 is output to the optical fiber 2 through the OLT1 in a predetermined channel.

An optical signal transmitted through the optical fiber 2 in the downstream direction is input to the first EO/OE section 21, converted into an electrical signal and output to the electrical line 23, and further divided into two paths, i.e., the second EO/OE22 and the ONU function section 27, by the electrical signal connection section 24.

The ONU function unit 27 acquires an electric signal of a predetermined channel and outputs the electric signal to the management function unit 26. The management function unit 26 performs control setting and various detection operations of the devices and various devices 25 in the first and second EO/OE units 21 and 22 included in the optical relay apparatus 4, based on the electric signal input from the ONU function unit 27. It should be noted that the control setting signal also includes setting signals of various parameters of the device.

The electric signal input from the electric line 23 to the second EO/OE unit 22 is converted into an optical signal and output to the optical fiber 3, and further transmitted to the plurality of ONUs 7-1, … 7-n through the optical coupler 5, whereby the respective ONUs 7-1, 7-n acquire signals distributed by the ONU function 8 b.

It should be noted that the optical signal is generally transmitted between the ONUs 7-1, 7-n and the OTL1 via the optical relay device 4, and the ONU is connected to an internet line or the like or a CATV center device or the like.

Therefore, if the functions of the system in the optical transmission system are logically shown, as shown in fig. 2, the ONU functional unit 27 of the optical relay apparatus 4 can configure the system with the same protocol standard as the ONU functions 8b of the ONUs 7-1, … 7-n, and therefore, the operations performed between the OTL1 and the ONUs 7-1, … 7-n can be used in the ONU functional unit 27 for the management function. Therefore, the management of the optical relay apparatus 4 provided on the optical transmission path between the OTL1 and the ONUs 7-1, 7-n for the purpose of long distance of the PON-type optical transmission system or the like can be efficiently multiplexed and accommodated on the optical transmission path without using a new other line and without affecting the existing operation.

(second embodiment)

Fig. 5 is a block diagram showing a configuration of an optical relay apparatus used in the optical transmission system according to the second embodiment of the present invention, and shows a configuration in which the optical relay apparatus 4 shown in fig. 1 is further embodied. In fig. 5, the same reference numerals as in fig. 1 denote the same elements.

In fig. 5, the electric line 23 connecting the first EO/OE section 21 and the second EO/OE section 22 has a first electric line 23a transmitting electric signals in the downstream direction and a second electric line 23b transmitting electric signals in the upstream direction. A first electrical signal connection unit 61 that branches an electrical signal to the ONU functional unit 27 and the drive circuit 68 is connected to a middle of the first electrical line 23 a. A second electrical signal connection unit 62 that multiplexes the output electrical signals of the predetermined channels output from the ONU functional unit 27 to the electrical signals on the second electrical line 23b is connected to the second electrical line 23 b. As the second electrical signal connection portion 62, for example, a buffer IC is used.

The first EO/OE section 21 has: a first WDM coupler 63 connected to the optical fiber 2 on the OTL1 side; a first light receiving element 64 for receiving the downstream optical signal separated by the first WDM coupler 63 and converting the downstream optical signal into an electrical signal; a first receiving circuit 65 that outputs an output electric signal of the first light receiving element 64 by performing 3R or 2R processing; a first drive circuit 66 that outputs a predetermined drive current in accordance with an upstream electric signal from the second electric line 23 b; the light generated by the injection of the drive current from the first drive circuit 66 is output to the light receiving element first light emitting element 67 of the optical fiber 2 via the first WDM coupler 63.

The second EO/OE section 22 has: a second drive circuit 68 that outputs a drive current in accordance with the downstream electric signal from the first electric line 23 a; a second light emitting element 69 which outputs light by injection of a driving current from the second driving circuit 68; a second WDM coupler 70 that outputs light input from the second light emitting element 69 to the optical fiber 3 on the customer premises side; a second light receiving element 71 that receives the upstream optical signal transmitted from the optical fiber 3 via the second WDM coupler 70 and converts the upstream optical signal into an electrical signal; the output electric signal of the second light receiving element 71 is processed by 2R or 3R and then output to the second receiving circuit 72 of the second electric line 23 b. The first and second WDM couplers 63 and 70 may be circulators (circulators), and may be a configuration in which isolators are combined into 3dB couplers.

The management function unit 26 and the ONU function unit 27 have the same configurations as those of the first embodiment.

In the optical transmission system having the optical relay apparatus 4 as described above, the optical signal transmitted from the OTL1 on the center side is transmitted through the optical fiber 2, input to the first WDM coupler 63 in the first EO/OE unit 21, and further received by the first light receiving element 64, as shown in fig. 1. When the first light receiving element 64 converts the received optical signal into an electrical signal and outputs the electrical signal to the first receiving circuit 65, the first receiving circuit 65 performs 3R processing on the electrical signal and outputs the electrical signal to the first electric line 23 a.

The electric signal transmitted to the second EO/OE section 22 via the first electric line 23a is branched into two directions of the second drive circuit 68 and the ONU functional section 27 by the first electric signal connecting section 61.

The second drive circuit 68, to which the electric signal is input, causes the second light emitting element 69 to emit light at a predetermined wavelength, for example, 1.49 μm, by passing a current through the second light emitting element 69 based on the input electric signal. Further, the optical signal output from the second light emitting element 69 is output to the optical fiber 3 via the second WDM coupler 70, further split by the optical coupler 5, further transmitted through the optical fiber 6-1, … 6-n, and input to the plurality of ONUs 7-1, … 7-n.

The ONU functional unit 27 to which the electric signal is input selects a predetermined channel from the electric signal input from the first electric signal connecting unit 61 and outputs the selected channel to the management functional unit 26. Further, the management function unit 26 not only controls the outputs of the receiving circuits 35 and 42, for example, or controls the temperatures of the heaters and the like included in the various devices 25, but also acquires the temperature abnormality signals, which are data of the various devices 25, for example, the temperature sensors, or data of the device door opening and closing sensors, based on the signals of the predetermined channels.

On the other hand, the optical signals output from the ONUs 7-1, … 7-n on the customer premises side are combined by the optical coupler 5, transmitted through the optical fiber 3, further transmitted through the second WDM coupler 70 in the second EO/OE unit 22, and irradiated to the second light receiving element 71. The second light receiving element 71 converts the received optical signal into an electrical signal. The converted electric signal is subjected to 2R or 3R processing by the second receiving circuit 72 and is output to the second electric line 23 b.

The electric signal output from the second receiving circuit 72 is transmitted to the first drive circuit 66 of the first EO/OE section 21 via the second electric line 23b, but on the way, an electric signal of a predetermined channel is also added from the second electric signal connection section 62. The electric signal of the predetermined channel is a signal output from the management function unit 26 via the ONU function unit 27, and is a monitoring signal based on detection signals of the various devices 25, the light receiving elements 64 and 71, the receiving circuits 65 and 72, and the like.

The second drive circuit 66, to which the electric signal transmitted in the upward direction through the second electric line 23b is input, outputs a drive current to the light receiving element 67. The light receiving element 67 into which the drive current is injected converts the electric signal into an optical signal of a 1.3 μm band and outputs the optical signal to the first WDM coupler 63.

Further, the optical signal in the upstream direction output from the first WDM coupler 63 is transmitted through the optical fiber 2 to reach the OTL1 on the center side, and the data obtained from the optical signal is monitored by the monitoring operation device 60 via the management machine 59.

According to the optical relay device described above, in the electric line 23 electrically connecting the first EO/OE unit 21 and the second EO/OE unit 22, the first electric line 23a for transmitting electric signals in the downstream direction is connected to the first electric signal connection portion 61 for branching electric signals, and the second electric line 23b for multiplexing electric signals is connected to the second electric signal connection portion 61 for multiplexing electric signals.

Therefore, since the ONU function section 27 is connected to the first and second electrical signal connection sections 61, and the system is configured with the same protocol standard as the ONU function 8b of the ONU 7-1, … 7-n at the customer premises, the operation performed between the PON standard 1 and the ONU 7-1, … 7-n can be used for transmission and reception of the management signal. Further, since the interface for connecting the management signal for managing the optical relay apparatus 1 to the optical transmission line is the ONU functional unit 27 which processes the electrical signal without providing the optical transceiver, the interface is implemented by a serial electronic configuration as compared with the case of connecting the signal to the optical transmission line with an optical signal, and therefore, the cost reduction is achieved.

(third embodiment)

Fig. 6 is a diagram showing an optical transmission system according to a third embodiment of the present invention, and the same reference numerals as in fig. 1 denote the same elements.

In fig. 6, a plurality of optical relay devices 4-1, … 4-m having the same configuration as the optical relay device 4 shown in fig. 1 are connected between the OTL1 and the optical coupler 5 via the optical fiber 2a, and the number thereof is increased, whereby further long distance optical transmission can be realized.

Thus, it is not necessary to provide an electric communication line for management of the optical relay devices 4-1, … 4-m or another line dedicated for management, such as an optical transmission line having a wavelength different from that of the optical relay devices 4-1, … 4-m for management, and the management signal can be multiplexed onto the existing PON optical transmission line by the ONU functional units 27 for electric signals.

The ONU functional units 27 in the optical relay apparatuses 4-1, … 4-m are substantially the same as the ONU functional units 8b of the ONUs 7-1, … 7-n on the customer premises side, and when fig. 6 is shown by a logical configuration, the ONU functional units 27 in the optical relay apparatuses 4-1, … 4-m are logically configured by the existing PON protocol standard as shown in fig. 7, so that the operations of the OTL1 and the ONUs 7-1, … 7-n can be used for the ONU functional units 27 in the optical relay apparatuses 4-1, … 4-m.

Note that the channels of the optical signals used by the plurality of optical relay devices 4-1, … 4-m are set to be different by passing the optical signals through the ONU functional units 27.

As described above, according to the optical relay device used in the optical transmission system according to the first to third embodiments of the present invention, the ONU function that can perform connection by an electrical signal can omit components such as an optical transceiver and a coupler constituting the ONU used on the customer premises side and optical connection, while the ONU function unit 27 for management disposed in the optical relay device can realize cost reduction using the conventional ONU function design and IC components. In addition, since the ONU function section 27 for management is not connected to the optical transmission line by light, the operation between the existing OLT and ONU function section can be utilized by connecting the ONU function by electricity without losing the optical allowable loss of the relay.

Further, according to the optical transmission system using the optical relay apparatus, since the optical relay apparatus having the ONU function section capable of connecting with an electric signal is used between the OLT constituting the center side of the PON system and the ONU at the customer premises side, it is possible to easily multiplex and connect the management functions such as monitoring and control of the optical relay apparatus to the PON line by the PON standard protocol without using another line for management, and there is an advantage that it is possible to easily integrate management of the ONU for the subscriber line and management of the optical relay apparatus.

(fourth embodiment)

Fig. 1 is a configuration diagram of a PDS type optical transmission system according to a fourth embodiment of the present invention.

In fig. 8, an optical transmission line such as CATV, which is formed of optical fibers 2 and 3 connected to an Optical Line Terminal (OLT)1 on the center side, is connected to a first optical coupler (optical wavelength multiplexer) 5 via an optical relay device 4. The optical transmission path branched into a plurality of paths by the first optical coupler 5 is connected to optical line terminal units (ONU) 7-1, … 7-n (n: natural number) of a plurality of customer premises via optical fibers 6-1, … 6-n. The ONUs 7-1 and … 7-n are each configured by an optical transceiver 8a and an ONU function 8b connected thereto.

The optical relay apparatus 4 includes: a first EO/OE section (electric/optical conversion unit) 21 connected to the optical fiber 2 on the OTL1 side; a second EO/OE section (electrical/optical conversion unit) 22 connected to the optical transmission path on the first optical coupler 5 side; an electric line 23 for transmitting an electric signal between the first EO/OE section 21 and the second EO/OE section 22; a second optical coupler (optical multiplexer/demultiplexer) 20 that branches an optical transmission line connected to the optical input/output end of the second EO/OE section 22 via an optical waveguide or optical fiber 19 in the downstream direction to 2 systems at least on the customer premises side, and connects the one system to the optical fiber 3 on the customer premises side; a management ONU28 optically connected to the second system on the downstream side of the second optical coupler (optical multiplexer/demultiplexer) 20; various devices 25 such as a door switch sensor, a temperature sensor, a power supply voltage sensor, an alarm, and a heater in the optical relay device 4; and a management function unit 26 connected to an electric signal input/output terminal of the management ONU24, and inputting/outputting a detection signal and a control setting signal to/from the first and second EO/OE units 21 and 22 and the various devices 25.

Note that the downstream is the direction of transmission from the center to the user house, and the upstream is the opposite direction.

The first and second EO/OE sections 21 and 22 and the electric wiring 23 electrically connecting these sections have the structure shown in fig. 9.

In fig. 9, an electric line 23 connecting the first EO/OE section 21 and the second EO/OE section 22 has a first electric line 23a transmitting electric signals in an upstream direction and a second electric line 23b transmitting electric signals in a downstream direction.

The first EO/OE section 21 has: a first WDM coupler 63 connected to the optical fiber 2 on the OTL1 side; a first light receiving element 64 that converts the downstream optical signal received by the first WDM coupler 63 into an electrical signal; a first receiving circuit 65 that outputs an output electric signal of the first light receiving element 64 by performing 3R or 2R processing; further comprising: a first drive circuit 66 that outputs a predetermined drive current in accordance with an upstream electric signal from the second electric line 23 b; the light generated by the supply of the drive current from the first drive circuit 66 is output to the first light emitting element 67 of the optical fiber 2 via the first WDM coupler 63.

The second EO/OE section 22 has: a second drive circuit 6 that outputs a predetermined drive current in accordance with a downstream electric signal from the first electric line 23 a; a second light emitting element 69 that outputs light by supply of a driving current from the second driving circuit 68; a second WDM coupler 70 that outputs light input from the second light emitting element 69 to the optical fiber 19 on the second optical coupler 20 side; further comprising: a second light receiving element 71 that receives the upstream optical signal transmitted from the second optical coupler 20 side via the second WDM coupler 70 and converts the upstream optical signal into an electrical signal; the output electric signal of the second light receiving element 71 is subjected to 2R or 3R processing and output to the second receiving circuit 72 of the second electric line 23 b. Note that 2R is a process of identifying reproduction and retiming, and 3R is a process of adding equalization amplification to these processes.

The management ONU28 is a device of the protocol standard of the PON interface, has the same circuit configuration as the ONUs 7-1 and … 7-n on the customer premises side, and includes an optical transceiver 28a and an OUN function unit 28b electrically connected thereto, as shown in fig. 10.

In fig. 10, the optical transceiver 28a includes: a WDM part 11 connected to an optical fiber 18 optically coupled to the second WDM coupler 70 via a second optical coupler 20; a photoelectric conversion circuit unit 12 having a light receiving element (not shown) connected to one optical waveguide path branched by the WDM unit 11; and an electro-optical conversion circuit 13 of a light emitting element (not shown) connected to the other optical waveguide path branched by the WDM section 11.

The ONU functional unit 28b is an electric circuit, and a plc 10/100 is connected to an ONU LSI31 for PON processing having an input/output unit connected to the photoelectric conversion circuit unit 12 and the photoelectric conversion circuit 13

A first LAN interface 35 consisting of PHY controller 32, transformer 33 and RJ25 connector 34, a second LAN interface 39 consisting of 10/100/1000PHY controller 36, transformer 37 and RJ25 connector 38, ZBT-RAM 40 and data bus 41. Further, an SRAM42 and a flash memory 43 are connected to the bus data bus 41, and a program and the like are stored in the flash memory 43. The RJ45 connectors 34 and 38 are plugged with plugs (not shown) connected to the management signal input/output terminals of the management function unit 25.

Although not shown in the drawings, device signals such as alarms of various devices 25 may be electrically connected to GPIO interfaces in the LSI31, and temperature sensors and the like in various devices 25 may be electrically connected to I2C interfaces in the LSI31 via analog-digital conversion boards.

The management function section 26 is a monitoring control setting circuit configuration that inputs the status monitoring signals of the first and second EO/OE sections 21, 22 and the device signals in the various devices 25, and outputs signals that can control the respective devices or setting conditions in the first and second EO/OE sections 21, 22 and the various devices 25.

In fig. 8, reference numeral 15 denotes a management machine connected to the OTL1, and 16 denotes a monitoring operation device which inputs and outputs signals to and from the management machine 15 and monitors and operates the optical relay apparatus 4.

In the optical transmission system having the optical relay apparatus as described above, optical signals in the 1.3 μm band of wavelengths transmitted from ONUs 7-1, … 7-n in the customer premises via optical fibers 6-1, … 6-n are combined by the first optical coupler 5, transmitted to the optical fiber 3, and input to the optical relay apparatus 4.

The optical signals input from the customer premises side into the optical relay device 4 are combined into an optical signal from the management ONU24 by the second optical coupler 20, converted into an electrical signal in the second EO/OE unit 22 through the optical fiber 19, input into the first EO/OE unit 22 through the electric line 23, converted into an optical signal, and output to the optical fiber 2 on the OLT1 side.

That is, in fig. 9, the optical signal input from the optical fiber 19 to the second WDM coupler 70 is converted into an electrical signal by the second light receiving element 71, then subjected to 2R processing or 3R processing by the second receiving circuit 72, and output to the first driving circuit 66 via the second electric line 23 b. The first light-emitting element 67 is driven by the drive current output from the first drive circuit 66, and the optical signal of the wavelength 1.3 μm band output from the first light-emitting element 67 is output to the optical fiber 2 via the first WDM coupler 63.

On the other hand, an optical signal having a wavelength of 1.49 μm output from the OLT1 is transmitted through the optical fiber 2, input to the first EO/OE unit 21, converted into an electrical signal, and input to the second EO/OE unit 22 via the electrical line 23 to be restored to the optical signal. The optical signal output from the second EO/OE section 22 is transmitted into the optical fiber 19 and the second optical coupler 20.

That is, in fig. 9, the optical signal input to the first WDM coupler 63 is converted into an electrical signal by the first light receiving element 64, then subjected to 3R or 2R processing by the first receiving circuit 65, and output to the second driving circuit 68 via the first electric line 23 a. The second light emitting element 69 is driven by the drive current output from the second drive circuit 68, and the optical signal is output to the optical fiber 19 via the second WDM coupler 70.

The optical signal transmitted in the downstream direction from the optical fiber 19 is branched by the second coupler 20, and a part of the optical signal is further branched by the first optical coupler 5 and then transmitted to the ONUs 7-1, … 7-n on the customer premises side via the optical fibers 6-1, … 6-n.

However, the management function unit 26 in the optical relay apparatus 4 sends the detection signals, the abnormality signals, and the like input from the first and second EO/OE units 21 and 22 and the various devices 25 to the ONU function unit 28b of the management ONU28 as electrical signals. The ONU functional unit 28b performs processing for making the input electrical signal a predetermined channel, that is, an ONU logical channel corresponding to the management ONU, and outputs the signal to the optical transceiver 28 a. The optical transceiver 28a converts the electrical signal into an optical signal of a wavelength 1.3 μm band and outputs the optical signal to the second optical coupler 20 in a predetermined channel. Note that the predetermined channel is a channel that cannot be selected by the user's house.

The optical signal of a predetermined channel input to the optical transceiver 28a is synthesized by the second optical coupler 20 into an optical signal transmitted from the customer premises side, and transmitted to the second EO/OE section 22, and further transmitted to the OLT1 via the electrical signal line 23, the first EO/OE section 21, and the optical fiber 2.

On the other hand, the control setting signal for management of the optical signal of the predetermined channel outputted from the OLT1 from the monitoring operation device 60 via the management machine 59 is inputted to the first EO/OE unit 21 via the optical fiber 2 at a wavelength of 1.49 μm together with other optical signals, converted into an electric signal, and then inputted to the second EO/OE unit 22 via the electric line 23, where it is restored to an optical signal. The optical signal output from the second EO/OE unit 22 is split by the second coupler 20 and output to the management ONU28 and the first optical coupler 5.

When the optical transceiver 28a converts the input optical signal into an electrical signal and transmits the electrical signal to the ONU function unit 28b in the management ONU28, the ONU function unit 28b outputs a predetermined channel of the input signal to the management function unit 26 as a management control setting signal.

The management function unit 26 sets parameters of the various devices 25 to predetermined values or controls the devices of the EO/OE units 21 and 22 in accordance with the management control setting signal. The EO/OE units 21 and 22 are controlled by adjusting the optical output powers of the light emitting elements 67 and 69, detecting command signals output from the light receiving elements 64 and 71, and the like. Examples of the parameters of the various devices 25 include a temperature setting of a heater and a strength setting of an alarm sound.

Note that, optical signals are generally transmitted between the ONUs 7-1, … 7-n and the OTL1 via the optical relay device 4, and the optical relay device is connected to an internet line or the like or a CATV center device or the like. In this case, among ONUs 7-1 and … 7-n, an optical signal of a channel other than a predetermined channel used for an optical signal from ONU28 for management is selected.

When logically representing the system functions in the optical transmission system, as shown in fig. 11, the management ONU28 of the optical relay apparatus 4 forms a system by the same protocol standard as the ONUs 7-1 and … 7-n of the user premises, and therefore, the operations performed between the OTL1 and the ONUs 7-1 and … 7-n can be used for the management ONU 28.

Therefore, the management of the optical relay apparatus 4 provided on the optical transmission path between the OTL1 and the ONUs 7-1, 7-n for the purpose of long distance of the PON-type optical transmission system or the like can be efficiently multiplexed and accommodated on the optical transmission path without using a new other line and without affecting the existing operation.

In this case, the second optical coupler 20 provided in the optical relay apparatus 4 needs to have a structure of at least two branches. Considering the difference in transmission distance from the ONU 7-1, … 7-n on the customer premises side in the intensity of the optical signal branched by the second optical coupler 20, it is preferable to minimize the power of the management ONU28 that is the shortest for the second optical coupler 20, for example, to 10%.

(fifth embodiment)

Fig. 12 is a block diagram showing a configuration of an optical transmission system according to a fifth embodiment of the present invention. In fig. 12, the same reference numerals as in fig. 8 denote the same elements, and the configuration is the same as that of the first embodiment except for the optical relay device.

The optical relay apparatus 4 shown in fig. 8 includes: a second optical coupler 20A connected to the optical fiber 2 on the OTL1 side; a first EO/OE section (electric/optical conversion unit) 21 connected to the first port on the downstream side through a second optical coupler 20; a second EO/OE unit (electrical/optical conversion unit) 22 connected to the optical fiber 3 on the customer premises side; an electric line 23 that transmits an electric signal between the first EO/OE section 21 and the second EO/OE section 22; a management ONU28 optically connected to the downstream second port of the second optical coupler 20A; various devices 25 installed in the optical relay apparatus 4; and a management function unit 26 connected to an electric signal input/output terminal of the management ONU28, and inputting/outputting a detection signal and a control setting signal to/from the first and second EO/OE units 21 and 22 and the various devices 25.

The first and second EO/OE units 21 and 22 and the electric line 23 connecting these units have the structure shown in fig. 9, as in the first embodiment.

In the optical transmission system having the optical relay device as described above, optical signals of a 1.3 μm band of wavelengths transmitted from the ONUs 7-1, … 7-n on the customer premises side are combined by the first optical coupler 5 and further input to the optical relay device 4 through the optical fibers 3, 6-1, … 6-n.

The optical signal input from the user house side to the optical relay device 4 is input to the second EO/OE unit 22, converted into an electrical signal, input to the first EO/OE unit 22 via the electric line 23, converted into an optical signal, and output to the second optical coupler 20A. The second optical coupler 20A combines the optical signal output from the first EO/OE unit 22 with the optical signal of the predetermined channel output from the management ONU28, and transmits the combined signal to the optical fiber 2 on the OLT1 side.

Here, the signal output from the management ONU28 is based on the optical signal output from the management function unit 26. That is, the management function unit 26 transmits detection signals, abnormality signals, and the like input from the first and second EO/OE units 21 and 22 and the various devices 25 constituting the optical relay apparatus 4 to the ONU function unit 28b of the management ONU 28. The ONU functional unit 28b transmits the input electrical signal to the optical transceiver 28a through a predetermined channel. The optical transceiver 28a converts the electrical signal input from the ONU functional unit 28b into an optical signal and outputs the optical signal to the second optical coupler 20A.

On the other hand, the optical signal of the wavelength 1.49 μm band output from the OLT1 is transmitted through the optical fiber 2, input to the second optical coupler 20A, split therefrom, and transmitted to the first EO/OE unit 21 and the management ONU 28.

The optical signal input to the first EO/OE unit 21 is converted into an electrical signal, and then input to the second EO/OE unit 22 via the electrical line 23 to be restored to an optical signal again. The optical signal output from the second EO/OE unit 22 is transmitted to the plurality of ONU 7-1, 7-n in the customer premises via the optical fiber 3 and the first optical coupler 5.

The control setting signal for management, which is an optical signal of a predetermined channel outputted from the monitoring operation device 16 to the OLT1 via the management unit 59, is inputted from the OLT1 to the second optical coupler 20A via the optical fiber 2, is branched therefrom, and is inputted to the ONU for management 28. It is noted that the signal output from OLT1 may be based on a signal from the network.

The optical transceiver 28a converts the optical signal input from the second optical coupler 20A to the management ONU28 into an electrical signal, and the ONU functional unit 28b outputs the signal of the predetermined channel to the management functional unit 26 as a management control setting signal. The management function section 26 sets parameters of various devices 25 to predetermined values or controls the devices of the EO/OE sections 21, 22 in accordance with the control setting signal for management.

Therefore, when logically representing the system functions in the optical transmission system, the management ONU28 of the optical relay apparatus 4 constitutes the system by the same protocol standard as the ONUs 7-1 and … 7-n of the user houses, as shown in fig. 11, so that the operations performed between the OTL1 and the ONUs 7-1 and … 7-n can be used in the management ONU 28.

Therefore, in order to efficiently accommodate the management of the optical relay apparatus 4 provided on the optical transmission path between the OTL1 and the ONUs 7-1, 7-n for the purpose of long distance of the PON-type optical transmission system or the like in multiple ways, a new line is not used and the existing operation is not affected.

The second optical coupler 20A provided in the optical relay apparatus 4 needs a structure of at least two branches. Further, in terms of the intensity of the optical signal branched by the second optical coupler 20A, when it is considered that the distribution to both the EO/OE21 and the management ONU28 and the maximum optical transmission distance between the OLT1 and the optical relay device 4 are ensured, it is preferable that the second optical coupler 20A performs equal distribution, for example, 50% to 50%, if the minimum light reception levels of the EO/OE21 and the management ONU28 are equal to each other.

In the case where the required optical transmission distance is compared with the embodiment of fig. 9 and the embodiment of fig. 12, in which the optical coupler 20 on the output side of the second EO/OE22 is not required, is more advantageous in the case where the transmission distance of the optical fiber 3 is mainly required to be increased, whereas the embodiment of fig. 8, in which the transmission distance of the optical fiber 2 is mainly required to be increased, is more advantageous.

Further, when it is assumed that the relay device 4 is out of order and the embodiment of fig. 8 and the embodiment of fig. 12 are compared, if the EO/OE21 and 22 in the relay device 4 is out of order due to a failure, the optical signal 18 cannot be transmitted to the OLT1 side in the embodiment of fig. 8 even if the management ONU28 normally operates, but the present embodiment shown in fig. 12 has an advantage that the information of the failure can be transmitted to the OLT1 side via the coupler 20A as long as the management ONU28 normally operates.

(sixth embodiment)

Fig. 13 is a diagram showing an optical transmission system according to a sixth embodiment of the present invention, and the same reference numerals as in fig. 8 denote the same elements.

In fig. 13, by connecting a plurality of relay devices 4-1, … 4-m having the same structure as the optical relay device 4 shown in fig. 8 or 12 at a distance via the optical fiber 2a between the OTL1 and the optical coupler 5 and increasing the number, further long distance of optical transmission can be realized.

Thus, it is not necessary to provide an electric communication line for management of the optical relay devices 4-1 and … 4-m or to provide another line for management such as an optical interface for management, and the management signal can be multiplexed to the existing PON optical transmission line by the ONU functional unit for electric signals.

The management ONU function 28 in the optical relay apparatuses 4-1 and … 4-m is substantially the same as the ONU 7-1 and … 7-n on the customer premises side, and when fig. 13 is shown by a logical configuration, the management ONU28 in the optical relay apparatuses 4-1 and … 4-m is logically configured by the existing PON protocol standard as shown in fig. 14, and therefore, the operations of the OTL1 and the ONU 7-1 and … 7-n can be used.

As described above, according to the fourth to sixth embodiments, since the management ONU28 performs signal combining or splitting via the second optical coupler 20A or the optical coupler 20 on the optical transmission lines 2 and 3 between the OLT1 and the first optical coupler 5 in the optical relay apparatus 4, it is possible to minimize (optimize) the optical loss to the ONU28 for management, and therefore, it is possible to configure the management ONU28 while maximally securing the optical allowable loss of the optical transmission line 2 or the optical transmission line 3 for main signals, and to use the operation between the existing OLT and the ONU functional unit.

Further, according to the optical transmission system using the optical relay apparatus, there are advantages as follows: the optical relay apparatus 4 can be managed by an optical signal having the same wavelength as that of the subscriber premises, and it is not necessary to lay a new optical communication line by a special wavelength or multiplex an optical signal for the subscriber using an optical signal processing apparatus having a different wavelength.

Claims (12)

1. An optical relay device for use in a PON type optical transmission system in which a center-side optical line terminal device and at least one subscriber-side optical line terminal device are connected via a passive-type optical transmission line,

the optical relay device includes:

a first electro-optical conversion unit connected to the optical transmission line at the center-side optical line termination device end to perform photoelectric conversion and electro-optical conversion;

a second electro-optical conversion unit connected to the optical transmission path at the subscriber-side optical line termination device end to perform photoelectric conversion and electro-optical conversion;

an electrical signal connection portion provided in an electrical line connecting the first and second electro-optical conversion units;

an ONU function unit connected to the electrical signal connection unit and processing the signal according to a protocol standard of a PON interface; and

a management function unit connected to the ONU function unit to perform monitoring control,

the management function unit inputs and monitors a device signal and a sensor measurement value indicating a state of a predetermined device including the first electrical-to-optical conversion unit and the second electrical-to-optical conversion unit via a GPIO interface or an I2C interface provided in the ONU function unit,

and the ONU function unit multiplexes the relay device management signal including the equipment signal and the sensor measurement value, which is input from the management function unit, on a predetermined channel of the upstream signal input from the subscriber-side optical line terminal device via the electrical signal connection unit, and transmits the multiplexed signal to the center-side optical line terminal device via the electrical signal connection unit.

2. The optical relay according to claim 1,

the predetermined channel is a maintenance channel defined by the PON protocol standard.

3. An optical transmission system comprising:

the optical relay device according to claim 1 or 2;

a center-side optical line terminating device connected to the optical relay device via a passive first optical transmission line; and

and one or more subscriber-side optical line terminating devices connected to the optical relay device via a passive second optical transmission line.

4. The light delivery system of claim 3,

the plurality of optical relay devices are connected via the first optical transmission line or the second optical transmission line.

5. An optical relay device, which is provided in an optical transmission path between at least one subscriber premises-side optical line terminal device and a center-side optical line terminal device,

the optical relay device includes:

an optical signal processing unit interposed between a first optical transmission line on the center side and a second optical transmission line on the user house side in the optical transmission lines;

an optical multiplexer/demultiplexer connected to the first or second optical transmission line; and

and a management optical line terminator that inputs/outputs a management electrical signal and is connected to the first or second optical transmission line via the optical multiplexer/demultiplexer.

6. The optical relay according to claim 5,

the management optical line termination device has the same function as the optical line termination device disposed on the customer premises side.

7. The optical relay according to claim 5 or 6,

the management optical line termination device is connected to one of the first optical transmission line and the second optical transmission line via the optical multiplexer/demultiplexer.

8. The optical relay according to claim 5 or 6,

the optical signal processing unit includes:

a first electro-optical conversion unit connected to the first optical transmission line on the center side, and performing photoelectric conversion and electro-optical conversion;

a second electro-optical conversion unit connected to the second optical transmission path on the user side, and performing photoelectric conversion and electro-optical conversion; and

and an electric line connected between the first and second electro-optical conversion units and transmitting an electric signal therebetween.

9. The optical relay according to claim 8,

at least one of the first electro-optical conversion unit and the second electro-optical conversion unit has a processing circuit for performing processing of equalization amplification, recognition reproduction, and retiming.

10. An optical transmission system comprising:

the optical relay device according to claim 5 or 6;

a first optical line termination device in the center-side optical line termination device connected to the optical repeater device via the first optical transmission line; and

and a second optical line terminating device in the subscriber premises optical line terminating device connected to the optical repeater via the second optical transmission line.

11. The light delivery system of claim 10,

the second optical transmission line is connected to the plurality of second optical line termination devices via an optical multiplexer/demultiplexer.

12. The light delivery system of claim 10,

the optical relay apparatus is connected to a plurality of optical transmission lines.