JP6036393B2 - Optical transmission system and optical transmission device - Google Patents

Description

The present invention relates to an optical transmission system and an optical transmission apparatus that transmit and receive optical signals through an optical transmission line.

  2. Description of the Related Art In recent years, with the rapid spread of the Internet, development and introduction of a wavelength division multiplexing (WDM) optical transmission system that transmits optical signals of a plurality of wavelengths all over a single optical fiber is progressing. At present, the transmission rate per wavelength is mainly from 2.4 Gbps to 10 Gbps, but a higher transmission rate such as 40 Gbps is beginning to be adopted in order to meet the ever-increasing information transmission demand.

  Since such a WDM optical transmission system is a system that relays signals in multiple stages without changing the light, the presence or absence of a failure in the transmission section is detected by monitoring the optical level of each node. In a WDM optical transmission system, generally, performance monitor information is collected at regular intervals of 15 minutes or 1 day. This performance monitor information includes the maximum value and minimum value of the light level within a certain period, and is stored at each node. When a code error (bit error) is detected in the transponder due to a decrease in the optical level in the transmission section, the network maintainer checks the performance monitor information of each node near the code error detection time, Can be identified. Patent Document 1 discloses an optical transmission apparatus in which the generation time is left as a history together with the maximum value and the minimum value for 15 minutes or one day.

JP 2009-210802 A

  However, in the conventional technology as described above, when a plurality of light level drops occur within 15 minutes or one day, it is not possible to confirm the exact relationship between the light level drop and a code error. It's not easy. In addition, since the maximum and minimum values of the optical level at each node and the history of the time of occurrence are stored in each node, if a code error occurs in a certain node, the network maintainer It is necessary to collect the history of performance monitor information for all nodes, and it takes time to identify the location of failure.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an optical transmission system capable of easily identifying a location where a failure has occurred.

In one aspect, the optical transmission system may comprise a plurality of nodes, an optical transmission line for connecting said nodes, and a monitoring device for monitoring the status of the node and the optical transmission path. Each node, from a signal received from the preceding node, and optical demultiplexing section for demultiplexing the monitor control signal are multiplexed to the main signal, a variable optical attenuation section for attenuating the monitor control signal demultiplexed, the You may prepare. Further, each of the nodes converts the supervisory control signal output from the variable optical attenuator into an electrical signal, and performs identification and reproduction, and a code for detecting a code error in the identified and reproduced supervisory control signal. An error monitoring unit . Moreover, each node, so that the input level of the supervisory control signal to the light / electrical converter at the time of normal operation becomes the minimum input level or near the substantially code error in the code error monitoring unit is not detected to, may comprise an input level monitoring control unit that performs a first control for controlling the attenuation amount of the variable optical attenuation section. Also, each node, when the code error of the monitor control signal in the code error monitoring unit is detected, and notifies the information indicating that to the monitoring device, the light level variation in the received signal caused notification May be provided .
In another aspect, the optical transmission device includes an optical demultiplexing unit that demultiplexes the monitoring control signal combined with the main signal from the signal received from the preceding optical transmission device via the optical transmission path, and And a variable optical attenuator for attenuating the waved supervisory control signal. The optical transmission device may further include an optical / electrical conversion unit that converts the supervisory control signal output from the variable optical attenuating unit into an electrical signal, and performs identification and reproduction. Furthermore, the optical transmission apparatus may include a code error monitoring unit that detects a code error of the supervisory control signal that has been identified and reproduced. Further, in the optical transmission apparatus, the input level of the monitoring control signal to the optical / electrical conversion unit during normal operation is at or near the minimum input level at which no code error is substantially detected by the code error monitoring unit. As described above, an input level monitoring control unit for controlling the attenuation amount of the variable light attenuation unit may be provided. Furthermore, when a code error of the monitoring control signal is detected by the code error monitoring unit, a notification unit may be provided that notifies the monitoring device of information indicating that the received signal has changed in light level.

  It should be noted that any combination of the above-described constituent elements and a representation of the present invention converted between an apparatus, a method, a system, a program, a recording medium storing the program, and the like are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the optical transmission system which can make easy specification of the location where the failure generate | occur | produced can be provided.

It is a figure which shows the structure of the optical transmission system which concerns on embodiment of this invention. It is a figure for demonstrating the structure of the reception OSC part which concerns on embodiment of this invention. It is a flowchart for demonstrating the input level control of the monitoring control signal. It is a flowchart for demonstrating operation | movement of each node in normal operation. It is a figure for demonstrating the structure of the reception OSC part which concerns on another embodiment of this invention.

  FIG. 1 is a diagram showing a configuration of an optical transmission system 100 according to an embodiment of the present invention. As shown in FIG. 1, an optical transmission system 100 includes a transmission OADM (Optical Add-Drop Multiplexer) node 10, a reception OADM node 12, and a relay node 14 disposed between the transmission OADM node 10 and the reception OADM node 12. A first optical transmission line 16 that connects the transmission OADM node 10 and the relay node 14, a second optical transmission line 18 that connects the relay node 14 and the reception OADM node 12, and a monitoring device 20.

  In this embodiment, there is one relay node 14 disposed between the transmission OADM node 10 and the reception OADM node 12, but a plurality of relay nodes 14 may be disposed. In the present embodiment, transmission from the OADM node 10 to the OADM node 12 and a configuration for realizing it will be described using the OADM node 10 as a transmission node and the OADM node 12 as a reception node. You may be comprised so that bidirectional transmission is possible.

  First, the transmission OADM node 10 will be described. The transmission OADM node 10 includes a first transmission transponder (TRPN) 22_1 to an nth transmission transponder 22_n, a wavelength multiplexing unit 24, a transmission amplifier unit 26, a transmission OSC (Optical Supervisory Channel) unit 28, and an optical multiplexing unit 30. The apparatus monitoring control unit 32 is provided.

  Each of the first transmission transponder (TRPN) 22_1 to the n-th transmission transponder 22_n converts the optical main signal received from the client side into an optical main signal having a different wavelength and outputs the optical main signal to the wavelength multiplexing unit 24. The transmission rate of the optical main signal output from the first transmission transponder (TRPN) 22_1 to the n-th transmission transponder 22_n is, for example, 2.4 to 40 Gb / s. The wavelength multiplexing unit 24 wavelength-multiplexes n-wave optical main signals from n transmission transponders. The transmission amplifier unit 26 amplifies the wavelength multiplexed optical signal from the wavelength multiplexing unit 24. The transmission amplifier unit 26 may be, for example, an EDFA (Erbium Doped Fiber Amplifier).

  The transmission OSC unit 28 transmits a monitoring control signal (OSC signal). This monitoring control signal is a signal used for controlling and monitoring a node, and is transmitted and received between adjacent nodes. The supervisory control signal has a wavelength different from that of the optical main signal. The transmission rate of the monitoring control signal is lower than the transmission rate of the main signal, for example, about 1.5 to 150 Mb / s. The device monitoring control unit 32 performs setting control and monitoring for each unit of the transmission OADM node 10, and communicates with an adjacent node (that is, the relay node 14) via a monitoring control signal.

  The optical multiplexing unit 30 combines the wavelength multiplexed optical signal amplified by the transmission amplifier unit 26 and the supervisory control signal output from the transmission OSC unit 28, and outputs the multiplexed signal to the first optical transmission line 16. As can be seen from FIG. 1, only the optical main signal is amplified by the transmission amplifier unit 26, and the supervisory control signal is output to the first optical transmission line 16 without passing through the transmission amplifier unit 26.

  Next, the relay node 14 will be described. The relay node 14 includes an optical demultiplexing unit 34, a reception OSC unit 36, a reception amplifier unit 38, a transmission amplifier unit 40, an optical multiplexing unit 42, a transmission OSC unit 44, and a device monitoring control unit 46. .

  The optical demultiplexing unit 34 demultiplexes the optical signal received from the first optical transmission line 16 into the wavelength multiplexed optical signal of the optical main signal and the supervisory control signal. The demultiplexed wavelength multiplexed optical signal is output to the reception amplifier unit 38. On the other hand, the demultiplexed monitoring control signal is output to the reception OSC unit 36.

  The reception OSC unit 36 performs optical / electrical conversion processing, signal termination processing, and the like on the monitoring control signal that is an optical signal. The monitoring control signal terminated at the reception OSC unit 36 is output to the device monitoring control unit 46. A detailed configuration of the reception OSC unit 36 will be described later.

  The reception amplifier unit 38 includes an optical branching unit 48, an optical amplifier 50, and a level monitor 52. The optical branching unit 48 outputs a part of the wavelength multiplexed optical signal to the level monitor 52 and outputs the rest to the optical amplifier 50. The level monitor 52 monitors the input level to the reception amplifier unit 38 and outputs the monitoring result to the device monitoring control unit 46. The optical amplifier 50 amplifies the wavelength multiplexed optical signal and outputs it to the transmission amplifier unit 40.

  The transmission amplifier unit 40 amplifies the received wavelength multiplexed optical signal and outputs it to the optical multiplexing unit 42. The transmission OSC unit 44 transmits a monitoring control signal. The device monitoring control unit 46 performs setting control and monitoring for each unit of the relay node 14 and communicates with adjacent nodes (that is, the transmission OADM node 10 and the reception OADM node 12) via a monitoring control signal.

  The optical multiplexing unit 42 combines the wavelength multiplexed optical signal amplified by the transmission amplifier unit 40 and the supervisory control signal output from the transmission OSC unit 44 and outputs the multiplexed signal to the second optical transmission line 18. As can be seen from FIG. 1, only the optical main signal is amplified by the transmission amplifier unit 40, and the supervisory control signal is output to the second optical transmission line 18 without passing through the transmission amplifier unit 40.

  Next, the receiving OADM node 12 will be described. The reception OADM node 12 includes an optical demultiplexing unit 54, a reception amplifier unit 56, a wavelength separation unit 58, a first reception transponder 60_1 to an nth reception transponder 60_n, a reception OSC unit 62, and a device monitoring control unit 64. Is provided.

  The optical demultiplexing unit 54 demultiplexes the optical signal received from the second optical transmission line 18 into the wavelength multiplexed optical signal of the optical main signal and the supervisory control signal. The demultiplexed wavelength multiplexed optical signal is output to the reception amplifier unit 56. On the other hand, the demultiplexed monitoring control signal is output to the reception OSC unit 62.

  The reception OSC unit 62 performs optical / electrical conversion processing, signal termination processing, and the like on the monitoring control signal that is an optical signal. The supervisory control signal terminated at the reception OSC unit 62 is output to the device supervisory control unit 64. The detailed configuration of the reception OSC unit 62 will be described later.

  The reception amplifier unit 56 includes an optical branching unit 66, an optical amplifier 68, and a level monitor 70. The optical branching unit 66 outputs a part of the wavelength multiplexed optical signal to the level monitor 70 and outputs the rest to the optical amplifier 68. The level monitor 70 monitors the input level to the reception amplifier unit 56 and outputs the monitoring result to the device monitoring control unit 64. The optical amplifier 68 amplifies the wavelength multiplexed optical signal and outputs it to the wavelength separation unit 58.

  The wavelength demultiplexing unit 58 separates the wavelength multiplexed optical signal into n-wave optical main signals and outputs each optical main signal to the first reception transponder 60_1 to the n-th reception transponder 60_n. Each receiving transponder performs predetermined signal processing such as optical / electrical conversion, timing extraction, and identification reproduction on the received optical main signal, and then transmits the optical main signal to the client side. Each receiving tunneler is configured to be able to detect a code error in the received optical main signal. When a code error of the optical main signal is detected, each reception transponder outputs code error detection information to the apparatus monitoring control unit 64.

  The device monitoring control unit 64 performs setting control and monitoring for each unit of the reception OADM node 12, and communicates with an adjacent node (that is, the relay node 14) via a monitoring control signal.

  The monitoring device 20 monitors the operating states of all nodes of the optical transmission system 100, that is, the transmission OADM node 10, the relay node 14, and the reception OADM node 12, and acquires an alarm notified from each node, Various information notified by each node is acquired. In addition, the monitoring device 20 uses the alarm and information from the transmission OADM node 10, the relay node 14, and the reception OADM node 12, so that the optical transmission line between the nodes, that is, the first optical transmission line 16 and the second optical transmission line. 18 is monitored for failure. A maintenance person of the optical transmission system 100 can check the status of each node and the optical transmission path between the nodes by accessing the monitoring device 20.

  All of the nodes included in the optical transmission system 100, that is, the transmission OADM node 10, the relay node 14, and the reception OADM node 12 are communicably connected. In FIG. 1, the transmission OADM node 10, the relay node 14, and the monitoring device 20 are all directly connected to the monitoring device 20, but it is sufficient that at least one node is directly connected to the monitoring device 20. It is possible to communicate with the monitoring device 20 using the monitoring control signal. Further, if the optical transmission system 100 is directly connected to the transmission OADM node 10 and the reception OADM node 12 located at both ends, for example, even when a failure occurs in the transmission OADM node 10 or the first optical transmission line 16. The relay node 14 can be accessed via the receiving OADM node 12 and the second optical transmission line 18.

  FIG. 2 is a diagram for explaining the configuration of the reception OSC unit according to the embodiment of the present invention. Here, the reception OSC unit 62 of the reception OADM node 12 will be described as an example, but reception OSC units of other nodes such as the reception OSC unit 36 of the relay node 14 have the same configuration.

  As shown in FIG. 2, the reception OSC unit 62 includes a variable optical attenuating unit 73, an optical level monitoring unit 72, an optical / electrical conversion unit 74, a code error monitoring unit 76, and an input level monitoring control unit 78. Prepare.

  As described above, the optical signal input from the second optical transmission line 18 to the reception OADM node 12 is demultiplexed by the optical demultiplexing unit 54 into the wavelength multiplexed optical signal of the optical main signal and the supervisory control signal. The demultiplexed wavelength multiplexed optical signal is output to the reception amplifier unit 56, and the supervisory control signal is output to the variable optical attenuation unit 73 of the reception OSC unit 62.

  A variable optical attenuator (VOA) 73 attenuates the input supervisory control signal and outputs it to the optical / electrical converter 74. The amount of attenuation of the variable light attenuating unit 73 is controlled by the input level monitoring control unit 78.

  The optical level monitor unit 72 is disposed between the variable optical attenuating unit 73 and the optical / electrical conversion unit 74 and detects the input level of the monitoring control signal to the optical / electrical conversion unit 74. The optical level monitor 72 receives, for example, a coupler that branches a part of the supervisory control signal from the variable optical attenuator 73 to the optical / electrical converter 74 and a part of the supervisory control signal branched by the coupler. It is composed of a PD (Photo Diode) that converts the signal. The input level information of the monitoring control signal to the optical / electrical conversion unit 74 detected by the optical level monitoring unit 72 is sent to the input level monitoring control unit 78.

  The optical / electrical converter 74 is a light receiving element such as a PD or APD (avalanche photodiode) that receives an input supervisory control signal and converts it into an electrical signal, a timing extraction circuit that extracts a clock signal from the electrical signal, and a clock signal An identification / reproduction circuit for identifying and reproducing electrical signals is used. The electrical monitoring control signal identified and reproduced by the optical / electrical conversion unit 74 is output to the code error monitoring unit 76.

  The code error monitoring unit 76 detects a code error (bit error) in the supervisory control signal that has been identified and reproduced. The detected code error information of the monitoring control signal is output to the input level monitoring control unit 78. The monitoring control signal that has passed through the code error monitoring unit 76 is input to the device monitoring control unit 64 via the input level monitoring control unit 78.

  The input level monitoring control unit 78 is based on the input level of the monitoring control signal to the optical / electrical conversion unit 74 detected by the optical level monitoring unit 72 and the code error information detected by the code error monitoring unit 76. The attenuation amount of the variable light attenuating unit 73 is controlled. In the present embodiment, the input level monitoring control unit 78 is configured such that the input level of the monitoring control signal to the optical / electrical conversion unit 74 during normal operation is such that the code error monitoring unit 76 does not substantially detect a code error. The attenuation amount of the variable light attenuating unit 73 is controlled so as to be at or near the level. The vicinity of the minimum input level is a vicinity in a range where no code error occurs.

The “minimum input level at which no code error is substantially detected” is the minimum input power necessary to achieve a bit error rate (BER) that can be regarded as error-free. This minimum input level differs depending on the transmission speed of the monitoring control signal, the type of light receiving element used in the optical / electrical converter 74, and the like. For example, when the transmission rate of the monitoring control signal is 155 Mb / s and an APD is used as the light receiving element, an input level of about −45 dBm is required to achieve a BER of about 1 × 10 ⁻¹⁰ .

  As described above, since the minimum input level varies depending on various factors, in this embodiment, control of the input level of the monitoring control signal to the optical / electrical conversion unit 74, that is, variable is appropriately performed for each reception OSC unit of each node. The attenuation amount of the light attenuation unit 73 is controlled.

  FIG. 3 is a flowchart for explaining the input level control of the monitoring control signal. The control shown in FIG. 3 is performed, for example, when the optical transmission system 100 is activated or when the optical transmission path is restored. In these cases, a monitoring control signal is sent from the transmission OSC unit of the adjacent adjacent node.

  First, the input level monitoring control unit 78 checks whether or not the monitoring control signal is normally received (S10). When the monitoring control signal is not received (N in S10), the process waits until the monitoring control signal is received.

  On the other hand, when the monitoring control signal is received (Y in S10), the input level monitoring control unit 78 starts adjusting the input level of the monitoring control signal to the optical / electrical conversion unit 74 (S12). First, the input level monitoring control unit 78 checks whether the attenuation amount of the variable optical attenuation unit 73 is minimum, that is, 0 dB (S14). When the attenuation amount of the variable optical attenuation unit 73 is not 0 dB (N in S14), the input level monitoring control unit 78 instructs the variable optical attenuation unit 73 to set the attenuation amount to 0 dB (S16), and returns to S14 again.

  When the attenuation amount of the variable optical attenuating unit 73 is 0 dB (Y in S14), the input level monitoring control unit 78 includes the input level information from the optical level monitoring unit 72, the code error information from the code error monitoring unit 76, and The amount of attenuation of the variable light attenuating unit 73 is gradually increased while the input level to the optical / electrical converter 74 is lowered. Specifically, the input level monitoring control unit 78 issues an instruction to increase the attenuation amount of the variable optical attenuation unit 73 by 1 dB (S18), and checks whether the code error monitoring unit 76 has detected a code error (S20). If no code error is detected (N in S20), the process returns to S18, and the attenuation is further increased by 1 dB.

  When the code error is detected by the code error monitoring unit 76 (Y in S20), the input level monitoring control unit 78 decreases the attenuation amount of the variable optical attenuation unit 73 by 1 dB (S22). Then, the input level monitoring control unit 78 checks whether or not the code error has been recovered (S24), and if it has not recovered (N in S24), the attenuation level is further decreased by 1 dB in S22. On the other hand, if the code error has been recovered (Y in S24), input level control of the supervisory control signal to the optical / electrical converter 74 is completed. By performing the control as shown in the flowchart of FIG. 3, the input level of the monitoring control signal to the optical / electrical conversion unit 74 can be controlled to be at or near the minimum input level.

  As described above, in this embodiment, the input level of the monitoring control signal to the optical / electrical conversion unit 74 during normal operation is controlled to be at or near the minimum input level. Therefore, when an optical level fluctuation (for example, several dB to several tens dB) occurs in the optical signal propagated through the second optical transmission line 18 during normal operation, a code error is immediately detected by the code error monitoring unit 76. Detected. When a code error is detected by the code error monitoring unit 76, the notification unit 80 of the device monitoring control unit 64 notifies the monitoring device 20 of code error occurrence information. When the input level of the supervisory control signal to the optical / electrical converter 74 is lowered during normal operation and a code error is detected, the input level supervisory controller 78 controls the attenuation of the variable optical attenuator 73. The current attenuation is maintained without performing the above.

  On the other hand, when the second optical transmission line 18 is disconnected during normal operation, the optical level monitor 72 detects the input of the monitoring control signal. In this case, the notification unit 80 of the device monitoring control unit 64 notifies the monitoring device 20 of the input interruption occurrence information.

  FIG. 4 is a flowchart for explaining the operation of each node during normal operation. Here, the receiving OADM node 12 will be described as an example, but the operation of other nodes is the same.

  The input level monitoring control unit 78 checks whether a code error of the monitoring control signal is detected by the code error monitoring unit 76 during normal operation (S30). When the code error of the monitoring control signal is detected by the code error monitoring unit 76 (Y in S30), the notification unit 80 of the device monitoring control unit 64 sends the code error occurrence information to the monitoring device 20 that monitors the entire optical transmission system 100. (S32). Then, the input level monitoring controller 78 maintains the current attenuation without controlling the attenuation of the variable optical attenuator 73 (S34). This completes the control when a code error in the supervisory control signal is detected.

  On the other hand, when the code error of the monitoring control signal is not detected by the code error monitoring unit 76 (N in S30), it is confirmed whether the input interruption of the monitoring control signal is detected by the optical level monitoring unit 72 (S36). When the input interruption of the monitoring control signal is not detected (N in S36), the process returns to S30.

  When the disconnection of the monitoring control signal is detected (Y in S36), the notification unit 80 of the device monitoring control unit 64 notifies the monitoring device 20 of the input disconnection occurrence information (S38). Thereafter, the input level monitoring controller 78 instructs the variable optical attenuator 73 so that the attenuation amount becomes 0 dB (S40). Then, the input level monitoring control unit 78 confirms whether or not the attenuation amount of the variable light attenuation unit 73 becomes 0 dB (S42), and if the attenuation amount is not 0 dB, instructs the variable light attenuation unit 73 again (in S42). N). On the other hand, if the attenuation amount of the variable optical attenuating unit 73 is 0 dB (Y in S42), the control when the input interruption of the monitoring control signal is detected is finished, and the optical transmission path is awaiting restoration. .

  If an optical level fluctuation occurs in some optical transmission line of the optical transmission system 100 during normal operation, a code error may be detected by the reception transponder of the reception OADM node 12 in some cases. The code error information detected by the reception transponder is sent to the monitoring device 20 as an alarm. Here, in the optical transmission system 100 according to the present embodiment, the code error occurrence information of the monitoring control signal is notified from each node to the monitoring device 20, so that the optical level fluctuation occurs in any optical transmission line of the optical transmission system 100. It can be easily identified whether it occurred. For example, when a code error in the supervisory control signal is detected by the reception OSC unit 36 of the relay node 14, it can be identified that the optical level fluctuation has occurred in the first optical transmission line 16. Further, for example, when a sign error of the supervisory control signal is detected by the reception OSC unit 62 of the reception OADM node 12, it can be identified that the optical level fluctuation has occurred in the second optical transmission line 18.

  As described above, the transmission rate of the monitoring control signal is lower than the transmission rate of the main signal (2.4 to 40 Gb / s), for example, about 1.5 to 150 Mb / s. Accordingly, the dynamic range of the optical / electrical converter that receives the supervisory control signal (the signal level range that can be received without causing a code error) is larger than the dynamic range of the receiving transponder that receives the optical main signal. Therefore, for example, when the supervisory control signal branched by the optical demultiplexing unit is directly received by the optical / electrical conversion unit, the optical level variation (for example, a variation of several dB) is such that the optical transmission path is not completely disconnected. Even if a sign error of the optical main signal is detected by the reception transponder, there is a possibility that the sign error of the supervisory control signal does not occur. In such a case, it is difficult to specify in which optical transmission line the failure has occurred.

  In the optical transmission system 100 according to the present embodiment, the monitoring control signal input level to the optical / electrical conversion unit during normal operation is at or near the minimum input level at which no code error is substantially detected by the code error monitoring unit. Since the attenuation amount of the variable optical attenuator is controlled so that the optical signal propagating through the optical transmission path has an optical level fluctuation of about several dB, the sign error of the supervisory control signal Can be detected. As a result, it is possible to easily identify the location where a failure has occurred in the optical transmission line.

  Further, when a disconnection occurs in any optical transmission line of the optical transmission system 100 during normal operation, a LOS (Loss Of Signal) alarm is issued at the reception transponder of the reception OADM node 12. Here, in the optical transmission system 100 according to the present embodiment, since the monitoring device 20 is notified of the input interruption occurrence information of the monitoring control signal from each node, the optical transmission system 100 is disconnected in any optical transmission line. Can be easily identified. For example, when the reception OSC unit 36 of the relay node 14 detects the disconnection of the monitoring control signal, it can be identified that the disconnection has occurred in the first optical transmission line 16. For example, when the reception OSC unit 62 of the reception OADM node 12 detects that the monitoring control signal is disconnected, it can be identified that the second optical transmission line 18 is disconnected.

  In the flowchart of FIG. 4, after notifying the monitoring device 20 of the input interruption occurrence information (S38), the variable optical attenuation unit is controlled so that the attenuation amount becomes 0 dB (S40, S42). This is because the span loss may change before and after the failure when the optical fiber is replaced with another one in the recovery operation or the route of the optical transmission path is switched to another route. If the attenuation of the variable optical attenuator is large when the optical transmission line is restored, there is a possibility that the supervisory control signal from the transmission OSC unit of the adjacent adjacent node cannot be properly received due to a change in span loss. Therefore, in this embodiment, when an input interruption is detected, the attenuation amount of the variable optical attenuation unit is controlled to the minimum, that is, the attenuation amount = 0 dB. Then, it waits for the optical transmission line to recover in this state. By performing such control, even if the span loss of the optical transmission line after restoration is greater than before the failure occurrence, the supervisory control signal can be properly received, and the optical main signal line can be restored. it can.

  FIG. 5 is a diagram for explaining a configuration of a reception OSC unit according to another embodiment of the present invention. Here, the reception OSC unit 62 of the reception OADM node 12 will be described as an example. In the reception OSC unit 62 according to the present embodiment, the same or corresponding components as those of the embodiment shown in FIG.

  In the reception OSC unit 62 according to the present embodiment, a code error correction unit 77 is added between the optical / electrical conversion unit 74 and the code error monitoring unit 76. The code error correction unit 77 corrects the code error of the supervisory control signal identified and reproduced by the optical / electrical conversion unit 74. The error correction code method may be, for example, FEC (Forward Error Correction). The code error correction unit 77 sends the monitoring control signal with the corrected code error to the device monitoring control unit 64 via the input level monitoring control unit 78. The code error correction unit 77 counts the number of code error corrections and notifies the code error monitoring unit 76 of the code error correction number information. The code error monitoring unit 76 according to the present embodiment detects a code error in the monitoring control signal based on the number of code error corrections from the code error correction unit 77. The code error information detected by the code error monitoring unit 76 is output to the input level monitoring control unit 78. The input level control method of the monitor control signal by the input level monitor controller 78 is the same as that of the embodiment shown in FIG.

  In this embodiment, even if a code error occurs in the supervisory control signal due to a decrease in the input level of the supervisory control signal to the optical / electrical converter 74, the code error correction part 77 converts the supervisory control signal into a code error. Since the correction can be made, the communication quality of the monitoring control signal can be improved. This embodiment is effective when the monitoring control signal is used as a user channel (a channel that the user can use for monitoring purposes separately from the main signal).

  In the above-described embodiment, the input level of the monitoring control signal to the optical / electrical conversion unit during normal operation is controlled to be at or near the minimum input level. However, the input level of the monitoring control signal to the optical / electrical converter may be controlled to an input level obtained by adding a predetermined margin to the minimum input level. This margin is for allowing a light level fluctuation of, for example, about 1 to 2 dB in the optical transmission line. This margin may be appropriately changed by a maintenance person of the optical transmission system 100.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

  In the above-described embodiment shown in FIG. 1, the point-to-point optical transmission system is disclosed. However, the present invention is not limited to the point-to-point optical transmission system, and the optical transmission such as a ring network or a mesh network is performed. It is also applicable to the system.

  DESCRIPTION OF SYMBOLS 10 Transmission OADM node, 12 Reception OADM node, 14 Relay node, 16 1st optical transmission line, 18 2nd optical transmission line, 20 Monitoring apparatus, 24 Wavelength multiplexing part, 26 Transmission amplifier part, 28 Transmission OSC part, 30, 42 Optical multiplexing unit, 32, 46, 64 Device monitoring control unit, 34, 48, 54 Optical demultiplexing unit, 36, 62 Reception OSC unit, 38, 56 Reception amplifier unit, 40 Transmission amplifier unit, 44 Transmission OSC unit, 58 wavelengths Separation unit, 72 optical level monitoring unit, 73 variable optical attenuation unit, 74 optical / electrical conversion unit, 76 code error monitoring unit, 77 code error correction unit, 78 input level monitoring control unit, 80 notification unit, 100 optical transmission system.

Claims (4)

Multiple nodes,
An optical transmission line connecting the nodes;
E Bei a monitoring device for monitoring the status of the node and the optical transmission path,
Each node
An optical demultiplexing unit for demultiplexing the supervisory control signal combined with the main signal from the signal received from the previous node ;
A variable optical attenuator for attenuating the demultiplexed supervisory control signal;
An optical / electrical converter that converts the supervisory control signal output from the variable optical attenuator into an electrical signal for identification and reproduction;
A code error monitoring unit for detecting a code error of the identified and reproduced supervisory control signal;
The variable optical attenuating unit so that the input level of the monitoring control signal to the optical / electrical conversion unit during normal operation is at or near the minimum input level at which no code error is substantially detected by the code error monitoring unit. An input level monitoring control unit for performing a first control for controlling the attenuation amount of
A notification unit for notifying the monitoring device of information indicating that a light level variation has occurred when a code error of a monitoring control signal is detected by the code error monitoring unit;
The optical transmission system, characterized in that it comprises a.   Each node further includes an optical level monitoring unit that detects an input level of a monitoring control signal to the optical / electrical conversion unit,
  When the optical level monitor unit detects a monitoring control signal input disconnection, the notification unit notifies the monitoring device of the input disconnection occurrence information,
  The input level monitoring control unit performs a second control for controlling the variable optical attenuation unit so that the attenuation amount is minimized until a monitoring control signal is input. When the monitoring control signal is input, the input level monitoring control unit performs the second control. The optical transmission system according to claim 1, wherein control 1 is performed. Before filling power level monitoring control unit, in the first control to control the variable optical attenuating unit such that attenuation is minimized, after monitor control signal was confirmed that received normally, the optical / electrical conversion the optical transmission system according to claim 1 or 2 input level of the supervisory control signal to the part is characterized by controlling the attenuation amount of the minimum input level or the variable optical attenuation section so that the vicinity thereof.   An optical demultiplexing unit that demultiplexes the supervisory control signal combined with the main signal from the signal received via the optical transmission line from the optical transmission device in the previous stage;
  A variable optical attenuator for attenuating the demultiplexed supervisory control signal;
  An optical / electrical converter that converts the supervisory control signal output from the variable optical attenuator into an electrical signal for identification and reproduction;
  A code error monitoring unit for detecting a code error of the identified and reproduced supervisory control signal;
  The variable optical attenuating unit so that the input level of the monitoring control signal to the optical / electrical conversion unit during normal operation is at or near the minimum input level at which no code error is substantially detected by the code error monitoring unit. An input level monitoring control unit for controlling the attenuation amount of
  A notification unit for notifying a monitoring device of information indicating that a light level variation has occurred when a code error of a monitoring control signal is detected by the code error monitoring unit;
  An optical transmission device comprising:

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