JP2011023831A - Wdm-pon system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a WDM-PON system that flexibly responds to the band needs of ONUs. <P>SOLUTION: The WDM-PON system has: a plurality of subscriber terminals and a station-side terminating device; a wavelength multiplexer/demultiplexer that multiplexes up-signals from the plurality of subscriber terminals and wavelength-splits a down-signal from the station-side terminating device; and a splitter that multiplexes the down-signal from the station-side terminating device and power-splits the up-signals from the plurality of subscriber terminals. The station-side terminating device has a plurality of transmission units and a plurality of receiving units. Each of the plurality of transmission units includes a variable wavelength light source. Each of the plurality of receiving units includes a variable wavelength filter in the pre-stage. The plurality of variable wavelength light sources respectively transmit optical signals of a plurality of wavelengths by time division. The station-side terminating device sets each transparent wavelength of the plurality of variable wavelength filters while following each variable wavelength light source. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a WDM (Wavelength Division Multiplexing) -PON (Passive Optical Network) system using a multi-wavelength light source.

  The PON system is an economical system that can share a transmission line fiber and a station-side terminal device (hereinafter referred to as OLT: Optical Line Terminal) with a plurality of subscriber-side terminals (hereinafter referred to as ONUs). With the increase in traffic, the bandwidth has been increasing. However, the TDM (Time-Division Multiplexing) method is up to 10 Gbps for the first time, and the bandwidth beyond that is WDM-PON, as was the case with backbone transmission systems. Is promising.

  As a configuration of WDM-PON, AWG (Array Waveguide Gratings) is generally arranged on both the OLT / ONU side as in Non-Patent Documents 1, 2, and 3.

  Recently, a part of the downstream signal from the OLT side in WDM-PON is amplified and remodulated using RSOA (Reflective Semiconductor Optical Amplifier) or REAM (Reflective Electroabsorption Modulator) and reused as an upstream signal. The CLS method for removing the light source on the ONU side has been actively studied.

H. Takesue et al, ECOC2002, 8.5.6. (2002). C. Arellano et al., OFC / NFOEC2006, paper OTuC1 (2006). W. Hung et al., ECOC2003, We3.4.5 (2003).

  The configuration of the WDM-PON of Non-Patent Documents 1 to 3 described above is firstly unable to flexibly meet the bandwidth needs of the ONU, secondly cannot be Plug & Play when adding a new ONU, and thirdly is a transceiver in the OLT There is a problem such as being unable to automatically recover from a malfunction.

  An object of the present invention is to provide a WDM-PON system that can flexibly meet the bandwidth needs of ONUs. Still another object of the present invention is to enable Plug & Play when a new ONU is newly added and to automatically recover from a failure of a transceiver in the OLT according to another aspect of the present invention.

  In order to achieve the above object, a WDM-PON system of the present invention combines a plurality of subscriber terminals, a station-side terminator, uplink signals from the plurality of subscriber terminals, and the station-side termination. A wavelength multiplexer / demultiplexer that divides the downlink signal from the device, and a splitter that multiplexes the downlink signal from the station side termination device and power-divides the uplink signals from the plurality of subscriber terminals. The station-side termination device includes a plurality of transmitting units and a plurality of receiving units, each transmitting unit includes a wavelength tunable light source, each receiving unit includes a wavelength tunable filter in the previous stage, and Each of the wavelength tunable light sources transmits optical signals of a plurality of wavelengths in a time-sharing manner, and the station-side terminal device follows the respective wavelength tunable light sources to set the transmission wavelengths of the plurality of wavelength tunable filters.

  According to the present invention, a station-side terminal device (OLT) generates and transmits a downstream signal with a wavelength tunable light source, and receives an upstream signal branched by a splitter through a wavelength tunable filter that has the same wavelength as the downstream signal. Therefore, the wavelength and the assigned ONU can be changed for each OLT transceiver. For this reason, the OLT can flexibly cope with a change in ONU bandwidth needs by changing the allocation.

1 is a block diagram showing a configuration of a bandwidth-adjustable WDM-PON system according to a first embodiment of the present invention. It is a block diagram which shows the structure of the conventional WDM-PON system. It is a block diagram which shows one structural example of ONU11-1 to 11-5 shown in FIG. 1 by the 1st Embodiment of this invention. It is a block diagram which shows the example of 1 structure of OLT transmitter-receiver 16-1 to 16-5 shown in FIG. 1 by the 1st Embodiment of this invention. It is the conceptual diagram which showed the operation | movement of the OLT transmitter-receiver 16-3 shown in FIG. 1 by the 1st Embodiment of this invention. Flow chart for changing the bandwidth from 3Gbps to 10Gbps 1Gbps → 3Gbps bandwidth change flowchart Flow chart of new ONU addition operation It is a block diagram which shows the structure of the WDM-PON system which can adjust a band by the 2nd Embodiment of this invention.

(First embodiment)
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a WDM-PON system 1 of the present embodiment. The ONUs 11-1 to 11-5 are connected to the AWG 13 through transmission lines 12-1 to 12-5. The AWG 13 multiplexes the upstream optical signals of each wavelength from each ONU, and branches the downstream optical signal group from the OLT 15 to the transmission lines 12-1 to 12-5 according to each wavelength. The AWG 13 is connected to the optical splitter 14 through a transmission line 12-11. The optical splitter 14 power-divides the upstream optical signal group into transmission lines 12-6 to 12-10, and these signal groups are input to the OLT transceivers 16-1 to 16-5 in the OLT 15. Further, the downstream optical signals of the respective wavelengths from the respective OLT transceivers 16-1 to 16-5 are multiplexed by the optical splitter 14 through the transmission lines 12-6 to 12-10. The OLT 15 controls each of the OLT transceivers 16-1 to 16-5. For convenience, the number of ONUs and OLT transceivers is only five, but the number is not limited.

  FIG. 2 is a block diagram showing a configuration of a conventional WDM-PON system. Configuration of the Present Invention FIG. 1 is characterized in that the AWG 23-2 used in the conventional example is changed to an optical splitter 14 and a wavelength tunable filter 45 described later is provided in the front stage of the receiving unit in each OLT transceiver. .

  FIG. 3 is a block diagram showing the configuration of the ONUs 11-1 to 11-5 shown in FIG. In FIG. 3, the transmission unit 32 includes a REAM 31. The REAM 31 is a device that reflects downstream signals, remodulates them, amplifies them, and reuses them as upstream signals. The receiving unit 34 receives a downlink signal. Here, the operation rate of the ONU is 10 Gbps. The control unit 33 controls the entire ONU.

  FIG. 4 is a block diagram illustrating a configuration example of the OLT transceivers 16-1 to 16-5 illustrated in FIG. In FIG. 4, the transmission unit 42 includes a wavelength variable light source 41. The wavelength variable light source 41 transmits an optical signal having a specific wavelength as a downlink signal. The receiving unit 44 includes a wavelength variable filter 45, and extracts and receives only the optical signal having the specific wavelength. The control unit 43 sets the wavelength of the optical signal generated by the wavelength tunable light source 41 and the transmission wavelength of the wavelength tunable filter 45. Here, the operation rate of the OLT transceiver is assumed to be 10 Gbps.

  Next, the bandwidth guarantee operation of the WDM-PON system according to the present embodiment will be described.

  In FIG. 1, the OLT transceiver 16-1 transmits only an optical signal having a wavelength of λ1 from the wavelength variable light source 41 in FIG. A part of the optical signal is received by the receiving unit 34 in FIG. 3 of the ONU 11-1, and the rest is reused and transmitted as an upstream signal by the REAM 31 in FIG. The OLT transceiver 16-1 receives only the uplink signal by setting the transmission wavelength of the wavelength tunable filter 45 in FIG. 4 to the same wavelength as the wavelength tunable light source 41 in FIG. The ONU 11-1 communicates only with the OLT transmitter / receiver 16-1, thereby having a bandwidth of 10 Gbps at the top and bottom.

  The OLT transceiver 16-2 sequentially transmits optical signals having wavelengths λ2 to λ4 in a time division manner from the wavelength variable light source 41 in FIG. s A part of the optical signal is received by the receiving unit 34 in FIG. 3 of the ONUs 11-2 to 11-4, and the rest is reused and transmitted as an upstream signal by the REAM 31 in FIG. The OLT transceiver 16-2 receives only the uplink signal by setting the transmission wavelength of the wavelength tunable filter 45 in FIG. 4 in conjunction with the same wavelength as the wavelength tunable light source 41 in FIG. The ONUs 11-2 to 11-4 communicate with only the OLT transmitter / receiver 16-2, thereby having an ONU average 3 Gbps bandwidth at the top and bottom.

  As shown in FIG. 5, the OLT transceiver 16-3 sequentially transmits optical signals having wavelengths of λ5 to λ14 in a time-sharing manner from the wavelength variable light source 41 in FIG. 4, and the optical signals are illustrated in the ONUs 11-5 to 11-14. 3 is partially received by the receiving unit 34, and the rest is reused and transmitted as an uplink signal by the REAM 31 shown in FIG. The OLT transceiver 16-3 receives only the upstream signal by setting the transmission wavelength of the wavelength tunable filter 45 in FIG. 4 in conjunction with the same wavelength as the wavelength tunable light source 41 in FIG. The ONU 11-5 and nine ONUs not shown in FIG. 1 communicate with only the OLT transmitter / receiver 16-3, so that each ONU has a bandwidth of 1 Gbps on the upper and lower sides.

  The OLT transmitter / receiver 16-4 sequentially transmits light of unused wavelengths from the wavelength tunable light source 41 in FIG. 4 in a time division manner, and the OLT transmitter / receiver 16-4 transmits the transmission wavelength of the wavelength tunable filter 45 in FIG. By setting in conjunction with the same wavelength as the wavelength tunable light source 41, the upstream signal having the same wavelength as the transmission wavelength is monitored, and the ONU to be connected in the future or the power saving ONU is monitored.

  The OLT transmitter / receiver 16-5 is in a standby (power saving) state and can be operated at any time under the control of the OLT 15.

  Bandwidth guarantee is realized by determining the number of ONUs sharing one OLT transceiver as described above. Here, it is assumed that ONUs sharing one OLT transceiver have equal bandwidths. Next, the band changing operation will be described.

  The operation of changing the bandwidth from 3 Gbps to 10 Gbps will be described with reference to the flowchart of FIG. When the bandwidth is changed from 3 Gbps to 10 Gbps due to the ONU 11-2 request (step S1) of the current 3 Gbps band user with which the OLT transceiver 16-2 was communicating, the OLT 15 has the wavelength λ2 of the OLT transceiver 16-2. Transmission is stopped (step S3). The OLT transmitter / receiver 16-2 stops transmission of the downstream signal having the wavelength λ2 (step S4). The OLT 15 operates, for example, the OLT transmitter / receiver 16-5 that is on standby, and communicates at 10 Gbps using the wavelength λ2 (step S5). The OLT transceiver 16-5 starts communication with the ONU 11-2 using the wavelength λ2 (step S6).

  The operation of changing the bandwidth from 1 Gbps to 3 Gbps will be described with reference to the flowchart of FIG. When the bandwidth is changed from 1 Gbps to 3 Gbps (step S12) in response to a request from the ONU 11-5 of the current 1 Gbps bandwidth user (step S11) that the OLT transceiver 16-3 is communicating with, the OLT 15 is switched to the OLT transceiver 16-3. The transmission of the wavelength λ5 is stopped (step S13). The OLT transmitter / receiver 16-3 stops transmission of the downstream signal having the wavelength λ5 (step S14). The OLT 15 checks whether, for example, the OLT transceiver 16-2 currently operating as a 3 Gbps band is free (step S15). If there is a free space (step S15: YES), the OLT 15 2 is communicated using wavelength λ5. The OLT transceiver 16-2 starts communication with the ONU 11-5 using the wavelength λ5 (step S6). If there is no free space (step S15: NO), the OLT 15 activates the standby OLT transceiver 16-5, for example, and communicates using the wavelength λ5 (step S17). The OLT transceiver 16-5 starts communication with the ONU 11-5 using the wavelength λ5 (step S18).

  As described above, the bandwidth can be changed automatically without user intervention according to the user's request, so that the management cost can be reduced. Next, the operation for adding a new ONU will be described with reference to the flowchart of FIG.

  For example, assume that an ONU 11-3 requesting a 3 Gbps bandwidth is newly added. First, since the OLT 15 recognizes that the ONU is a non-operating ONU, light having a wavelength of λ3 is supplied from the OLT transceiver 16-4 that monitors the non-operating or power-saving ONU (step 3). S31). When the ONU 11-3 is added (step S32), the ONU 11-3 detects the light having the wavelength of λ3, puts a new addition request signal, and returns it to the OLT transceiver 16-4 (step S33). The OLT transceiver 16-4 transmits the new addition request signal added to the uplink signal to the OLT 15 (step S34). The OLT 15 causes the OLT transceiver 16-4 that has received the new addition request signal of the ONU 11-3 to stop transmitting light having a wavelength of λ3 (step S35). The OLT transmitter / receiver 16-4 stops transmission of the downstream signal having the wavelength λ3 (step S36). The OLT 15 checks whether, for example, the OLT transmitter-receiver 16-2 currently operating as a 3 Gbps band is free (step S37). If there is a vacancy (step S37: YES), the OLT 15 causes the OLT transceiver 16-2 to communicate with the ONU 11-3 using the wavelength λ3 (step S38). If there is no vacancy (step S37: NO), the OLT 15 For example, the OLT transmitter / receiver 16-5 in standby is operated and communicated using the wavelength λ3 (step S39). The OLT transceiver 16-5 starts to communicate with the ONU 11-3 using the wavelength λ3 (step S40).

  As described above, Plug & Play can be realized for newly adding ONUs. Next, the operation when the OLT transceiver fails will be described.

  For example, when the OLT transmitter / receiver 16-1 fails, the OLT 15 operates the standby OLT transmitter / receiver 16-5, for example, to communicate with the wavelength λ1 and the bandwidth of 10 Gbps.

  For example, when the OLT transmitter / receiver 16-2 fails, the OLT 15 activates the standby OLT transmitter / receiver 16-5, for example, and communicates with wavelengths λ2, λ3, λ4, and each band of 3 Gbps.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to the drawings.

  FIG. 9 is a block diagram showing a configuration of the WDM-PON system 1a of the present embodiment. In FIG. 9, the ONUs 91-1 to 91-5 are connected to the AWG 93 via transmission lines 92-1 to 92-5, and the AWG 93 multiplexes the upstream optical signals of the respective wavelengths from the respective ONUs, and also performs the OLT 95-1. The downstream optical signal group from is branched into transmission lines 92-1 to 92-5 according to each wavelength. The AWG 93 is connected to the optical splitter 94 via the circulator 97 in the transmission line 92-11. The circulator 97 is connected to the AWG 98, and the AWG 98 wavelength-divides the upstream optical signal group into the transmission lines 92-12 to 92-16. . These signal groups are input to the OLT receivers 99-1 to 99-5 in the OLT 95-2, and the downstream optical signals of the respective wavelengths from the OLT transmitters 96-1 to 96-5 are transmitted on the transmission path. The light is combined by the optical splitter 94 through 92-6 to 92-10.

  The OLT transceivers 96-1 to 96-5 have the same configuration as the OLT transceiver shown in FIG. 4 except that the OLT transceivers 96-1 to 96-5 do not have the receiving unit 44. The OLT transceivers 99-1 to 99-5 have the same configuration as the OLT transceiver shown in FIG. 4 except that the transmitter 42 is not included.

  In this embodiment, a circulator 97 is further added to the first embodiment, and the transmission path is divided by transmission and reception on the OLT side, and the downstream signal is combined by the splitter 94 as in the first embodiment, and the upstream direction This signal is characterized in that the wavelength is branched by AWG98. Since there is no branch loss in the upstream direction, there is an advantage that it is not necessary to increase the transmission power of the ONU.

  As described in the first embodiment, since the transmission wavelength of the wavelength variable filter of the OLT receiver needs to be linked with the transmission wavelength of the wavelength variable light source of the OLT transmitter, the OLT transmission group and the OLT reception group exchange information. Need to be connected so that Although the OLT transmitter 96 and the OLT receiver 99 are shown separately, they may be integrated.

1, 1a WDM-PON system 11-1 to 11-4 ONU
12-1 to 12-11 Transmission path 13 AWG
14 Splitter 15 OLT
16-1 to 16-5 OLT transceiver 21-1 to 21-5 ONU
22-1 to 22-11 Transmission path 23-1 to 23-2 AWG
25 OLT
26-1 to 26-5 OLT transceiver 31 REAM
32 Transmitter 33 Control Unit 34 Receiver 41 Wavelength Variable Light Source 42 Transmitter 43 Controller 44 Receiver 45 Wavelength Tunable Filter 91-1 to 91-5 ONU
92-1 to 92-16 Transmission path 93 AWG
94 Splitter 95-1, 95-2 OLT
96-1 to 96-5 OLT transmitter 97 Circulator 98 AWG
99-1 to 99-5 OLT receiver

Claims (6)

A plurality of subscriber terminals, station-side terminal devices,
A wavelength multiplexer / demultiplexer that multiplexes upstream signals from the plurality of subscriber terminals and wavelength-divides the downstream signals from the station-side termination device;
A splitter that multiplexes downstream signals from the station-side terminal device and power-divides upstream signals from the plurality of subscriber terminals;
A WDM-PON system comprising:
The station-side termination device includes a plurality of transmission units and a plurality of reception units, each transmission unit includes a wavelength tunable light source, each reception unit includes a wavelength tunable filter in the previous stage, and the plurality of wavelengths Each of the variable light sources transmits an optical signal having a plurality of wavelengths in a time-sharing manner, and the station-side terminating device sets the transmission wavelengths of the plurality of wavelength tunable filters following the respective wavelength variable light sources. WDM-PON system. A plurality of subscriber terminals, station-side terminal devices,
A wavelength multiplexer / demultiplexer that multiplexes upstream signals from the plurality of subscriber terminals and wavelength-divides the downstream signals from the station-side termination device;
A splitter for multiplexing downstream signals from the station side termination device;
A circulator for branching an upstream signal group from the plurality of subscriber terminals; a wavelength multiplexer / demultiplexer for branching an upstream signal from the plurality of subscriber terminals;
A WDM-PON system comprising:
The station-side termination device includes a plurality of transmission units and a plurality of reception units, each transmission unit includes a wavelength tunable light source, each reception unit includes a wavelength tunable filter in the previous stage, and the plurality of wavelengths Each of the variable light sources transmits an optical signal having a plurality of wavelengths in a time-sharing manner, and the station-side terminating device sets the transmission wavelengths of the plurality of wavelength tunable filters following the respective wavelength variable light sources. WDM-PON system. The station side termination device is:
The bandwidth of the plurality of subscriber terminals is guaranteed by limiting the number of optical signals of a plurality of wavelengths transmitted by the wavelength tunable light source in a time division manner for each transmission unit of the plurality of station-side terminal devices. The WDM-PON system according to claim 1 or 2. In response to the bandwidth change request from the subscriber terminal, the transmitter of the station-side terminating device that supplies light of the wavelength corresponding to the subscriber-side terminal stops transmission of the wavelength,
The station side termination device is:
Search for the transmitting unit of the station-side terminal device corresponding to the requested bandwidth of the subscriber terminal, and if there is an available bandwidth in the transmitting unit, make the transmitting unit transmit the wavelength and check whether there is the transmitter 4. The transmitter according to claim 1, wherein, even if the transmitter is present, if there is no available bandwidth, the transmitter of the station-side terminating device that is in standby is activated to communicate with the wavelength and the band. The WDM-PON system according to item 1. The station side termination device is:
Including a monitoring transmitter that sequentially transmits time-division optical signals of wavelengths where the wavelength variable light source is not in operation;
The subscriber terminal is
When a new addition request signal is put on the optical signal of the self-addressed wavelength from the transmission unit of the station side termination device when newly added,
The station side termination device is:
When the monitoring transmission unit receives the new addition request signal, the monitoring transmission unit stops transmission of the wavelength, and a transmission unit corresponding to the request band of the newly added subscriber terminal is provided. If there is a bandwidth available in the transmission unit, the transmission unit transmits the wavelength, and if there is no transmitter or the transmitter is not available in the bandwidth, the waiting transmission unit The WDM-PON system according to any one of claims 1 to 4, wherein the WDM-PON system is activated and communicates in the wavelength band.   When a transmitter / receiver with the station-side terminator fails, the station-side terminator starts a standby transmitter / receiver, and communicates with the subscriber terminal at the wavelength and band with which the failed transmitter / receiver was communicating. The WDM-PON system according to claim 1, wherein the WDM-PON system is restarted.

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