Raman amplification device and raman amplification method

Abstract

To enable a Raman amplification device to suppress Auto Power Shut Down (APSD) at a time of an Optical Supervisory Channel (OSC) shutdown with a main signal in a canalized state.SOLUTION: A Raman amplification device inhibits APSD at a time of an OSC shut down with a main signal, being an optical signal, in a canalized state by: monitoring the canalized main signal (S801); switching Wavelength Division Multiplexing Loss of Signal (WDMLOS) detection threshold values for determining presence / absence of a WDMLOS output at a transmission path shutdown in accordance with whether or not a monitoring result of the main signal exceeds a predetermined condition (S803); and, for example, in the case where a wavelength number of the canalized main signal is larger than a certain wavelength number, e.g., a reference wavelength number, or in the case where whole power of the main signal is larger than a reference power, determining presence or absence of an APSD control, by using an APSD determination condition 1 based on AND of the OSC shutdown and the WDMLOS (S805), or otherwise, in the case where the wavelength number of the canalized main signal is less than the reference wavelength number, the whole power of the main signal is smaller than the reference power, determining the presence or absence of the APSD control, by using an APSD determination condition 2 based on the OSC shutdown (S804).SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a Raman amplifier and a Raman amplification method. [Background technology]

[0002] A Raman amplifier optically amplifies an optical signal in a transmission path such as an optical fiber based on Raman pump light. The Raman amplifier has a safety control function that cuts off the optical output using APSD (Auto Power Shut Down), preventing the laser light of optical power from being emitted outside and causing harm to the human body. The APSD stops the output of the optical amplifier when it detects that the end of the optical fiber has been opened.

[0003] Prior art includes, for example, a system that absorbs noise optical components such as ASE in wavelength bands outside the wavelength band of wavelength-multiplexed optical WDM, thereby detecting optical signal interruptions regardless of whether the number of wavelengths increases or decreases. In addition, when a link failure occurs in the west-east link, the east Raman module stops the Raman pump based on the absence of a pilot signal and stops the west Raman pump by sending a fault signal to the west link. Another system transmits WDM signals between multiple nodes, and the booster EDFA at each node switches from AGC to a low-power APC method based on in-band IB and out-of-band OB signals transmitted via an OSC. In addition to the OSC function, there is also a system that transmits SV signals, including the number of multiplexed wavelengths extracted from the WDM signal, via an inter-OSC communication bus that is different from the transmission path of the main signal, and transmits and receives management data such as the number of multiplexed wavelengths of the general line signal between nodes (see, for example, Patent Documents 1 to 4 listed below).

[0004] Above, WDM stands for Wavelength Division Multiplexing. ASE stands for Amplified Spontaneous Emission. EDFA stands for Erbium Doped Fiber Amplifier, and OSC stands for Optical Supervisory Channel. AGC stands for Auto Gain Control, and APC stands for Auto Power Control. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-66610 [Patent Document 2] U.S. Patent Application Publication No. 2010 / 0080553 [Patent Document 3] U.S. Patent Application Publication No. 2009 / 0142061 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-279355 Summary of the Invention [Problem to be solved by the invention]

[0006] For example, in a system where the Raman amplifier at the downstream node performs backward Raman excitation, even if the main signal is in a normal communication state, if the OSC is interrupted, the APSD function will be activated due to the influence of Raman noise, causing the main signal to be interrupted.

[0007] In one aspect, the present invention aims to be able to suppress APSD when an OSC is disconnected while a main signal is in a communication state in a Raman amplifier that performs Raman pumping. [Means for solving the problem]

[0008] According to one aspect of the present invention, a Raman amplifier that Raman-amplifies an optical signal on a transmission line by Raman pumping requires a control unit that monitors a main signal that is being communicated by the optical signal, switches a WDMLOS detection threshold that determines whether or not to output an alarm (WDMLOS) when the transmission line is cut off, depending on the monitoring result of the main signal, and if the monitoring result of the main signal that is being communicated exceeds a predetermined condition, determines whether or not to perform APSD control using APSD (Auto Power Shut Down) judgment condition 1 based on an OSC (Optical Supervisory Channel) cutoff and an accumulation of WDMLOS, and if the monitoring result of the main signal that is being communicated falls below the predetermined condition, determines whether or not to perform APSD control using APSD judgment condition 2 based on the OSC cutoff. [Effects of the Invention]

[0009] According to one aspect of the present invention, in a Raman amplifier that performs Raman pumping, it is possible to suppress APSD when an OSC is disconnected while a main signal is in a communication state. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an explanatory diagram of a Raman amplifier according to an embodiment. [Figure 2] Figure 2 is an explanatory diagram of the problems that arise with existing technology. (Part 1: When a transmission line fails) [Figure 3] Figure 3 is an explanatory diagram of the issues that arise with existing technology. (Part 2: When the OSC fails) [Figure 4A] Figure 4A is an explanatory diagram of the effect of Raman noise generated by backward Raman excitation. (Part 1) [Figure 4B] Figure 4B is an explanatory diagram of the effect of Raman noise generated by backward Raman excitation. (Part 2) [Figure 4C] Figure 4C is an explanatory diagram of the effect of Raman noise generated by backward Raman excitation. (Part 3) [Figure 5] FIG. 5 is an explanatory diagram of an example of control in the Raman amplifier according to the embodiment. [Figure 6]FIG. 6 is a functional block diagram of a Raman amplifier according to an embodiment. [Figure 7] FIG. 7 is a diagram illustrating an example of the hardware configuration of a control unit of a Raman amplifier. [Figure 8] FIG. 8 is a flowchart showing an outline of an example of APSD control processing performed by the Raman amplifier. [Figure 9] FIG. 9 is a chart showing an example of setting the WDMLOS detection threshold. [Figure 10A] FIG. 10A is a table showing a specific example of setting the WDMLOS detection threshold and the reference value of the number of wavelengths. (Part 1) [Figure 10B] FIG. 10B is a table showing specific examples of setting the WDMLOS detection threshold and the reference value of the number of wavelengths. (Part 2) [Figure 11] FIG. 11 is a table showing an example of setting the APSD determination conditions. [Figure 12] FIG. 12 is a flowchart showing an example of the overall processing of APSD control performed by the Raman amplifier. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the disclosed Raman amplifier will be described in detail with reference to the drawings.

[0012] (Configuration example of Raman amplifier according to embodiment) Fig. 1 is an explanatory diagram of a Raman amplifier according to an embodiment. In the example shown in Fig. 1, Raman amplifiers 100 are arranged at upstream Node A and downstream Node B, each having the same configuration, and transmit WDM light (main signal) via a transmission line 101 such as SMF. SMF stands for Single Mode Optical Fiber.

[0013] The transmission line 101 includes a downstream transmission line 101a from the upstream (Node A) Raman amplifier 100A to the downstream (Node B) Raman amplifier 100B, and an upstream transmission line 101b from the downstream (Node B) Raman amplifier 100B to the upstream (Node A) Raman amplifier 100A.

[0014] An example of the configuration in which the downstream (Node B) Raman amplifier 100B is the local station will be described below. The Raman amplifier 100 (100B) includes a Raman amplifier 111 and a ROADM 112. ROADM is an abbreviation for Reconfigurable Optical Add / Drop Multiplexer.

[0015] In the example of FIG. 1, the Raman amplifier 111 has an internal Raman pumping light source and performs Raman pumping on the transmission line 101a by backward pumping. The present invention is not limited to backward pumping, but can also be applied to forward pumping and Raman pumping that combines forward and backward pumping. In forward pumping, the Raman amplifier 111 is provided on the Raman amplifier 100A side to perform forward pumping on the transmission line 101a. The ROADM 112 includes a multiplexer / demultiplexer 121, an optical amplifier 123, a wavelength selective switch (WSS) 124, a multiplexer (MUX / DEMUX) 125, and an OSC optical transceiver 126. WSS stands for Wavelength Selective Switch.

[0016] In terms of the downstream transmission path 101a, the multiplexer / demultiplexer 121a separates the wavelength band of the OSC light for monitoring from the optical signal on the transmission path 101a and outputs the separated wavelength band to the OSC light transceiver 126. The OSC light transceiver 126 performs control based on the control signal included in the OSC light transmitted from the upstream (Node A) Raman amplifier 100A.

[0017] The optical amplifier 123a is, for example, an EDFA, and optically amplifies the optical signal on the transmission line 101a. The WSS 124a adds and drops any optical signal to and from the transmission line 101a. The multiplexer 125a multiplexes the optical signals input and output to the WSS 124.

[0018] Also, in terms of the upstream transmission path 101b, the WSS 124b adds and drops any optical signal to and from the transmission path 101b. The optical amplifier 123b optically amplifies the optical signal on the transmission path 101b. The OSC optical transceiver 126 incorporates fault information detected by its own Raman amplifier 100B into the OSC light. The OSC light is multiplexed with the main signal on the upstream transmission path 101b via the multiplexer / demultiplexer 121b and transmitted to the upstream (Node A) Raman amplifier 100A.

[0019] An example of the configuration of the upstream (Node A) Raman amplifier 100A is similar to the downstream (Node B) Raman amplifier 100B described above, and the same components are denoted by the same reference numerals.

[0020] The Raman amplifier 100B according to the embodiment performs the following controls 1. and 2. 1. The WDMLOS detection threshold is changed depending on the number of wavelengths of the main signal being communicated. For example, if the number of wavelengths is greater than a predetermined number, the WDMLOS detection threshold is increased accordingly. WDMLOS is an alarm that notifies of a loss state (loss of signal) in which the WDM main signal does not reach the receiving unit due to a fiber break in the transmission path 101, etc.

[0021] In FIG. 1 and the embodiments described below, a control example based on the "number of wavelengths" of the transmitted main signal (referred to as wavelength number control) will be mainly described. However, control based on the "power" of the transmitted main signal (referred to as power control) may also be performed. The "number of wavelengths" and "power" of the main signal have an equivalent relationship. Therefore, the "number of wavelengths" in FIG. 1 can be replaced with "power" in the following description. In the power control described below, control is performed, for example, based on the power of the entire band of the WDM main signal (total power). Furthermore, power control is not limited to total power, and may also be based on the power of a specified wavelength, for example, the power of one specified wavelength or the power of multiple wavelengths. Here, when the control in 1 above is performed using power control, the WDMLOS detection threshold is switched depending on the total power of the transmitted main signal.

[0022] 2. The APSD criteria are switched depending on the number of wavelengths of the main signal. The Raman amplifier 100B of the local station (Node B) performs APSD control based on preset APSD criteria, and switches these APSD criteria depending on the number of wavelengths of the main signal. Furthermore, when the control in 2 is performed using power control, the APSD criteria are switched depending on the total power of the main signal being transmitted.

[0023] The WDMLOS detection threshold can be set according to the power or number of wavelengths of the transmitted main signal. For example, the WDMLOS detection threshold may be variably set according to the power or number of wavelengths of the transmitted main signal, or may be set to a fixed value as follows. For example, as the number of wavelengths of the main signal increases, the minimum main signal power increases. In this case, the Raman amplifier 100 switches the WDMLOS detection threshold to a first setting value that increases it from the initial reference value. Furthermore, APSD determination condition 1 is set to the AND (integration) of OSC loss and WDMLOS detection. This allows WDMLOS to be output based on the WDMLOS detection threshold when a main signal loss (including OSC loss) occurs, and APSD can be applied based on the main signal loss. Furthermore, if only an OSC sudden failure (OSC loss) occurs, APSD is not applied, thereby avoiding any impact on the transmitted main signal.

[0024] Furthermore, if the number of wavelengths of the main signal decreases, the Raman amplifier 100 switches the APSD judgment condition to APSD judgment condition 2 = OSC loss only. At this time, the WDMLOS detection threshold is switched to a second setting value. The second setting value is different from and lower than the first setting value. For example, if the number of wavelengths of the main signal decreases below the reference number after operating the WDMLOS detection threshold at its initial value, the second setting value remains at the initial value (reference value) and is not changed. This is based on the fact that operation with a small number of wavelengths below a predetermined number is rare. Furthermore, if the number of wavelengths of the main signal decreases while operating the WDMLOS detection threshold at the first setting value, the WDMLOS detection threshold is changed to a second setting value (equivalent to the reference value) lower than the first setting value. This allows APSD to be applied based on (1) OSC loss. Furthermore, in power control, if the total power of the transmitted main signal decreases, the Raman amplifier 100 switches the APSD judgment condition to APSD judgment condition 2 = OSC loss only.

[0025] As a specific example, assume that the number of wavelengths of the main signal communicated between the Raman amplifier 100A of Node A is greater than a certain reference number of wavelengths, as shown in Fig. 1. Furthermore, assume that no loss of the main signal has been detected, but (0) an OSC loss has occurred in the OSC light from the Raman amplifier 100A of Node A.

[0026] In this case, the Raman amplifier 100B (1) detects an OSC interruption in the optical amplifier 123a, and (2) does not apply APSD by the optical amplifier 123b based on the APSD determination condition = OSC interruption & WDMLOS. "Not applying" APSD means control to "not perform" optical output blocking by APSD. "Applying" APSD means control to "perform" optical output blocking by APSD.

[0027] Furthermore, when the number of wavelengths of the main signal decreases below the reference number of wavelengths, the Raman amplifier 100 "applies" APSD if an OSC interruption is detected based on the APSD determination condition=OSC interruption.

[0028] In the Raman amplifier 100 that performs backward Raman pumping according to the embodiment, when the number of wavelengths is greater than the reference number of wavelengths and the transmission path 101 is in a normal communication state without fiber breaks (main signal breaks) as shown in FIG. 1, APSD is not applied (optical output is not blocked) simply because the OSC is broken. The relationship between the generated Raman noise, the number of wavelengths of the main signal, and the WDMLOS detection threshold will be described in detail later. This allows APSD control to be performed more accurately without being affected by Raman noise. APSD control is not limited to being performed based on the number of wavelengths as described above, but may also be performed based on power.

[0029] (Issues with existing technology) Here, the problems that arise in the existing technology will be explained. Figures 2 and 3 are explanatory diagrams of the problems that arise in the existing technology, and Figures 4A to 4C are explanatory diagrams of the influence of Raman noise that occurs in backward Raman pumping.

[0030] First, Fig. 2 shows the APSD control state when a transmission line failure occurs. Fig. 2(a) shows a ROADM without Raman amplification, and Fig. 2(b) shows a ROADM with Raman amplification. For convenience, in both Fig. 2(a) and Fig. 2(b), the same components as those in the Raman amplifier device 100 with Raman amplification described in Fig. 1 are denoted by the same reference numerals.

[0031] In the ROADM without Raman amplification shown in Figure 2(a), assume that a fiber cut (transmission line cut) occurs in the transmission line 101 between (0) NodeA (100A) and NodeB (100B). In this case, (1) NodeB (100B)'s optical amplifier 123a detects the main signal cut and the OSC cut. Although not shown in Figure 2(a), the optical amplifier 123a has a photodetector (PD), and the PD detects the main signal cut.

[0032] Then, (2) in Node B (100B), optical amplifier 123b applies APSD. As a result, (3) in Node A (100A), a fiber break is detected, and (4) APSD is applied. Thus, the APSD determination condition for a ROADM without Raman amplification is main signal break and OSC break.

[0033] In contrast, in the ROADM with Raman amplification shown in Figure 2(b), suppose that a fiber cut (transmission line cut) occurs in the transmission line 101 between (0)-1: Node A (100A) and Node B (100B). In this case, (0)-2: Raman noise (Raman noise power) of a predetermined power is generated on the transmission line 101 due to Raman noise light that is folded back at the fiber cut portion due to backward pumping by the Raman amplifier 111. In this case, (1) Node B (100B) cannot detect the main signal cut due to the influence of Raman noise, and the optical amplifier 123a detects only the OSC cut.

[0034] For this reason, in a ROADM with Raman amplification, (2) Node B (100B) causes optical amplifier 123b to apply APSD based on the OSC loss. As a result, (3) Node A (100A) detects the OSC loss and (4) applies APSD. For this reason, the APSD determination criterion for a ROADM with Raman amplification is OSC loss. As such, a ROADM with Raman amplification cannot correctly detect a loss of the main signal, and therefore cannot use main signal loss as an APSD determination criterion.

[0035] Next, the APSD control state when an OSC fails is shown in Figure 3. Figure 3(a) shows a ROADM without Raman amplification, and Figure 3(b) shows a ROADM with Raman amplification.

[0036] In the ROADM without Raman amplification shown in Figure 3(a), assume that an OSC interruption occurs at (0) NodeA (100A). In this case, (1) NodeB (100B)'s optical amplifier 123a detects the OSC interruption. Here, (2) NodeB (100B)'s optical amplifier 123b does not apply APSD. As described above, the APSD determination criteria for a ROADM without Raman amplification are main signal interruption and OSC interruption, so APSD is not applied based on OSC interruption alone.

[0037] 3(b), it is assumed that an OSC interruption occurs at (0) Node A (100A). In this case, at (1) Node B (100B), the optical amplifier 123a detects the OSC interruption.

[0038] Then, (2) in Node B (100B), optical amplifier 123b applies APSD based on the OSC loss. As a result, (3) in Node A (100A), the OSC loss is detected, and (4) APSD is applied. As described above, the APSD determination condition for ROADMs with Raman amplification is OSC loss. In this case, in a ROADM with Raman amplification, even if there is no main signal loss, APSD is applied due to the OSC loss, resulting in a main signal loss.

[0039] Next, problems that arise in the above-described ROADM with Raman amplification will be described with reference to FIGS. 4A to 4C.

[0040] FIG. 4A shows the signal states due to a transmission line break between Node A (100A) and Node B (100B). When a transmission line break occurs in transmission line 101a, the main signal transmitted from Node A (100A) is lost. However, when Raman amplifier 111 in Node B (100B) back-pumps transmission line 101a, the generated Raman noise remains and becomes noise. Here, as described above, PD 123p of optical amplifier 123a in Node B (100B) cannot detect the loss of the main signal. For this reason, Node B (100B) performs control to apply APSD when it detects an OSC light linkdown.

[0041] Therefore, even if the main signal is in a normal communication state at NodeB (100B), the optical amplifier 123a is shut down due to an OSC interruption such as a sudden failure of the OSC light, resulting in a main signal interruption during operation.

[0042] FIG. 4B shows the main signal and OSC light. The horizontal axis of FIG. 4B represents wavelength, and the vertical axis represents received power. FIG. 4B(a) shows the wavelength settings of the OSC light and the main signal. The OSC light and the main signal are in different wavelength bands and are wavelength-multiplexed and transmitted through the same optical fiber (transmission path 101). The main signal is WDM light, and the number of wavelengths of the main signal can range from 1 to 128, for example. The OSC light is one wave.

[0043] Figure 4B(b) shows the received power of the main signal and Raman noise shown in Figure 4A. The main signal and Raman noise each have a predetermined received power. As shown in Figure 4B(b), the Raman noise power may be greater than the main signal power depending on the number of wavelengths.

[0044] Here, even when the main signal is interrupted as shown in FIG. 4A and the received power of the main signal disappears, the NodeB (100B) detects the Raman noise power from the folded light due to backward Raman pumping.

[0045] Figure 4C shows the detection threshold for main signal loss. In NodeB (100B), the WDMLOS detection threshold Th for determining main signal loss is set to the same value regardless of the number of wavelengths transmitted in the main signal. When the main signal is lost, NodeB (100B) outputs WDMLOS.

[0046] The WDMLOS detection threshold Th shown in Figure 4C(a) is set to a value (dotted line in the figure) that allows WDMLOS to be detected even when only one wavelength is in operation. The WDMLOS detection threshold Th is the same value regardless of whether a Raman amplifier is used. However, in a configuration in which NodeB (100B) performs Raman amplification, the WDMLOS detection threshold Th shown in Figure 4(a) is set. In this case, when the main signal power is lost, it becomes impossible to determine that the main signal has been lost due to the influence of Raman noise power that is greater than the WDMLOS detection threshold Th.

[0047] For this reason, if the WDMLOS detection threshold Th is set high based on the case where the number of wavelengths is large, as shown in Fig. 4C(b), it will be possible to detect a loss of the main signal, but the number of wavelengths of the main signal will decrease and the received power of the main signal will fall below the WDMLOS detection threshold Th, resulting in an erroneous detection of a loss of the main signal.

[0048] To address the above-described problems, the Raman amplifier 100 performing backward Raman pumping according to the embodiment uses wavelength number control to monitor the number of wavelengths of the main signal in operation (transmission) on the transmission line 101 and switch the WDMLOS detection threshold and APSD judgment condition. However, the Raman amplifier 100 may also use power control to monitor the total power of the main signal in operation (transmission) and switch the WDMLOS detection threshold and APSD judgment condition.

[0049] (Control of the embodiment) 5A and 5B are diagrams illustrating an example of control in the Raman amplifier according to the embodiment. In the initial state shown in Fig. 5A, the WDMLOS detection threshold Th0 is set to a value (reference value) that allows detection of both the main signal and Raman noise.

[0050] Furthermore, as shown in Figure 5(b), when the number of wavelengths in the main signal is greater than a predetermined reference value, the minimum main signal power becomes higher. In this case, the Raman amplifier 100 switches the WDMLOS detection threshold Th0 to Th1 (first set value), which is increased by Δ, and also sets the APSD determination condition to 1. APSD determination condition = AND of OSC loss and WDMLOS. As a result, when a main signal loss occurs, this main signal loss state can be determined using the WDMLOS detection threshold Th1. Furthermore, if only the OSC loss occurs due to a sudden OSC failure, APSD is not applied, thereby avoiding any impact on the main signal in a continuous state.

[0051] Furthermore, as shown in FIG. 5(c), when the number of wavelengths of the main signal decreases, the Raman amplifier 100 sets APSD judgment condition 2: OSC interruption. At this time, the WDMLOS detection threshold Th remains unchanged at a second set value, for example, the initial value Th0. This is based on the fact that operation with a small number of wavelengths below the reference number is rare. This allows APSD to be applied based on the OSC interruption.

[0052] (Example of functional configuration of Raman amplifier) Fig. 6 is a functional block diagram of a Raman amplifier according to an embodiment. In Fig. 6, the same components as those of the NodeN (100B) described above are denoted by the same reference numerals. In Fig. 6, dotted lines indicate optical signals, and solid lines indicate electrical signals.

[0053] The Raman amplifier 100 includes the functions of the above-described Raman amplifier 111, multiplexer / demultiplexers 121a and 121b, and OSC optical transmitter / receiver 126. It also includes the functions of a main signal receiver 601, a WDMLOS detector 602, a monitor 603, a WDMLOS detection threshold switch 604, an APSD controller 605, a WDM optical transmitter 606, an APSD determination condition database 615, and setting information 616.

[0054] In the main signal receiving unit 601, the PD 123p detects the main signal transmitted from NndeA (100A) via the transmission path 101a, and the OCM 611 detects the number of wavelengths of the main signal. The main signal receiving unit 601 includes the optical amplifier 123a described above. OCM stands for Optical Channel Monitor. The WDMLOS detecting unit 602 outputs a WDMLOS signal when it detects a loss of the main signal detected by the PD 123p.

[0055] The monitor 603 monitors the number of wavelengths of the main signal detected by the OCM 611 using wavelength number control. In the case of power control, the monitor 603 monitors the total power of the main signal detected by the PD 123p. The WDMLOS detection threshold switching unit 604 switches the WDMLOS detection threshold Th according to the number of wavelengths of the main signal monitored by the monitor 603 and the WDMLOS detection threshold for each APSD determination condition held in the APSD determination condition database 615. The WDMLOS detection threshold Th may be switched based on the total power of the main signal instead of the number of wavelengths.

[0056] The WDM optical transmitter 606 includes the optical amplifier 123b described above, and transmits WDM light (main signal) to NodeA (100A) via the transmission line 101b.

[0057] The APSD control unit 605 performs APSD control based on whether or not there is an OSC interruption detected by the OSC optical transceiver 126 and whether or not there is a WDMLOS output from the WDMLOS detection unit 602. At this time, the APSD control unit 605 references an APSD determination condition database 615 and setting information 616. The setting information 616 holds information on the number of wavelengths set in the device, power information for each signal, bandwidth, and signal type information.

[0058] Then, in response to fluctuations in the number of wavelengths of the active main signal monitored by the monitoring unit 603, if the number of monitored wavelengths is greater than the number of wavelengths set in the device, as described above, the APSD control unit 605 sets the APSD judgment condition to AND condition 1: OSC loss and WDMLOS. If the number of wavelengths of the main signal decreases, the APSD judgment condition is switched to 2: OSC loss only.

[0059] The APSD control unit 605 may also switch the APSD judgment condition based on fluctuations in the number of wavelengths of the main signal using power control, rather than simply switching the APSD judgment condition based on fluctuations in the total power of the main signal using the wavelength count control described above. In the case of power control, for example, if the monitored total power is greater than a reference power set in the device, the APSD judgment condition is set to 1. APSD judgment condition = AND condition of OSC loss and WDMLOS. Furthermore, if the total power of the main signal decreases, the APSD judgment condition is switched to 2. APSD judgment condition = OSC loss only.

[0060] For wavelength count control, the monitoring unit 603 also obtains power information for each signal from the setting information 616. Because the number of wavelengths is determined based on the reference power, if there is a main signal with high power, it may be counted as more than one wavelength rather than one wavelength. The monitored main signals have different power levels per wavelength. Therefore, if the total power of the monitored main signals is twice the reference power, the monitoring unit 603 counts it as two wavelengths. Also, if the power of the main signals is lower than the reference power, it may count a wavelength number less than one, for example, 0.5 wavelengths. Note that if there is a relationship between the bandwidth, signal type, etc. and the signal power, the monitoring unit 603 may also obtain bandwidth and signal type information from the setting information 616. For example, the wider the bandwidth, the greater the signal power. This allows the method of counting wavelengths when controlling the wavelength count to accommodate fluctuating main signal power.

[0061] In addition, in an embodiment, the monitoring unit 603 may replace the power of the main signal being communicated with the corresponding number of wavelengths, replace the reference power with the reference number of wavelengths, and perform APSD control based on the replaced number of wavelengths and the reference number of wavelengths.

[0062] If the number of monitored wavelengths is greater than the number of wavelengths set in the device, the APSD control unit 605 shuts down the WDM optical transmitting unit 606 and the Raman amplifier 111 based on the AND condition of 1. APSD judgment condition = OSC interruption and WDMLOS. At this time, the APSD control unit 605 notifies the OSC optical transmitting and receiving unit 126 of an APSD request to NodeA (100A) using an OSC signal.

[0063] Furthermore, if the number of monitored wavelengths is less than the number of wavelengths set in the device, the APSD control unit 605 shuts down the WDM optical transmitting unit 606 and the Raman amplifier 111 based on 2. APSD judgment condition = OSC loss only. At this time, the APSD control unit 605 notifies the OSC optical transceiver unit 126 of an APSD request to NodeA (100A) using an OSC signal. Furthermore, in power control, the APSD control unit 605 may shut down the WDM optical transmitting unit 606 and the Raman amplifier 111 based on 2. APSD judgment condition = OSC loss only if the total power of the monitored main signals is less than the reference power set in the device.

[0064] (Example of hardware configuration of the control unit of a Raman amplifier) 7 is a diagram showing an example of the hardware configuration of the control unit of the Raman amplifier. For example, the function relating to the APSD control of the Raman amplifier 100 can be configured by general-purpose hardware shown in FIG.

[0065] Of the functions described in FIG. 6, mainly the APSD control unit 605, and further the functions related to signal processing, for example, the functions of performing electrical signal processing within the main signal receiving unit 601 to the WDM optical transmitting unit 606, can be realized using the hardware configuration shown in FIG. 7.

[0066] 7 includes a processor 701 such as a CPU (Central Processing Unit), a memory 702, a network IF 703, a recording medium IF 704, and a recording medium 705. The components are connected to each other via a bus 700.

[0067] Here, processor 701 is a control unit that mainly controls APSD control. Processor 701 may have multiple cores. Memory 702 includes, for example, a read-only memory (ROM), a random access memory (RAM), and a flash ROM. Specifically, for example, the flash ROM stores a control program, the ROM stores an application program, and the RAM is used as a work area for processor 701. The programs stored in memory 702 are loaded into processor 701, causing processor 701 to execute the coded processes.

[0068] The network IF 703 controls the interface with the network NW and controls the input and output of information to and from the outside. The network NW is not limited to a wired or wireless electrical transmission path, but may also use an optical transmission path via the transmission path 101, for example.

[0069] The recording medium IF 704 controls reading / writing of data from / to the recording medium 705 under the control of the processor 701. The recording medium 705 stores the data written under the control of the recording medium IF 704.

[0070] In addition to the above-mentioned components, for example, an input device, a display, etc. may be connectable via the IF.

[0071] The processor 701 shown in FIG. 7 can implement functions related to the APSD control unit 605 and the electrical signal processing in the main signal receiving unit 601 to the WDM optical transmitting unit 606 shown in FIG. 6 by executing a program.

[0072] (APSD control overview) Fig. 8 is a flowchart showing an example of APSD control processing performed by a Raman amplifier. Fig. 8 shows processing related to switching of APSD determination conditions, which is mainly executed by the APSD control unit 605 (processor 701 in Fig. 7) shown in Fig. 6.

[0073] First, the APSD control unit 605 monitors the main signal being communicated on the transmission path 101a (step S801). Next, the APSD control unit 605 determines whether the monitoring result of the communicated main signal monitored in step S801 exceeds a predetermined condition (step S802). The predetermined condition may be, for example, the number of wavelengths in wavelength number control or power in power control.

[0074] If the result of the determination shows that the monitoring result of the communicating main signal exceeds the predetermined condition (step S802: Yes), the APSD control unit 605 proceeds to the process of step S803. When the monitoring result of the main signal exceeds the predetermined condition, for example, in wavelength number control, this corresponds to a case where the number of wavelengths is greater than the reference number of wavelengths, and in power control, this corresponds to a case where the total power of the communicating main signal is greater than the reference power.

[0075] On the other hand, if the monitoring result of the communicating main signal falls below the predetermined condition (step S802: No), the APSD control unit 605 proceeds to the process of step S804. When the monitoring result of the main signal falls below the predetermined condition, for example, in wavelength number control, this corresponds to the case where the number of wavelengths is less than the reference number of wavelengths, and in power control, this corresponds to the case where the total power of the communicating main signal is less than the reference power.

[0076] In step S803, the APSD control unit 605 switches the WDMLOS detection threshold value Th (step S803). Here, the WDMLOS detection threshold value Th is switched from the initial setting reference value to a higher value in accordance with the number of connected wavelengths or the total power of the main signal. After this, the APSD control unit 605 sets the APSD determination condition to be the AND condition of OSC interruption and WDMLOS (step S805).

[0077] In step S804, the APSD control unit 605 sets the APSD determination condition to OSC interruption only (step S804). By the process of step S805 or step S804, the APSD control unit 605 ends the process of switching the APSD determination condition.

[0078] (Example of setting the WDMLOS detection threshold) FIG. 9 is a chart showing an example of setting the WDMLOS detection threshold. The horizontal axis of FIG. 9 is the number of wavelengths of the main signal, and the vertical axis is the received power of the main signal. The received power of the main signal indicates the minimum received power for each number of wavelengths. The WDMLOS detection threshold Th is set as a reference value to the number of wavelengths at which the main signal received power S in the main signal receiver 601 becomes greater than the power of the Raman noise N, based on the maximum Raman noise N, the fiber type (classification) of the transmission line 101, and the Raman gain of the Raman amplifier 111. In the explanation of FIG. 9, the horizontal axis can also be replaced with the set value (reference power) of the main signal power.

[0079] As shown in Fig. 9, the main signal reception power S has the characteristic that the reception power increases as the number of wavelengths increases, and the intersection point between the main signal reception power S and the maximum Raman noise N is seven wavelengths. In this case, if the WDMLOS detection threshold Th is set in a wavelength region X where the number of wavelengths is less than seven, it will not be possible to determine whether the main signal has been lost due to the influence of the Raman noise power.

[0080] On the other hand, if the WDMLOS detection threshold Th is set in region F where the number of wavelengths exceeds seven, it is possible to determine whether the main signal has been lost without being affected by the power of Raman noise. In the example shown in Fig. 9, the reference value of the WDMLOS detection threshold Th is set to 24 wavelengths as the number of wavelengths corresponding to the main signal reception power S, with a margin α (e.g., 3 dB) from the maximum Raman noise N for safety.

[0081] 10A and 10B are charts showing specific examples of setting the WDMLOS detection threshold and the reference value of the number of wavelengths.

[0082] Figure 10A is a chart showing the simulation results of the amount of Raman noise generated. The horizontal axis of Figure 10A is Raman gain, and the vertical axis is Raman noise amount. When the fiber type of transmission line 101 is SMF (Single Mode Fiber), the Raman gain target is 12 dB. Based on these two parameters, the fiber type and Raman gain target, a Raman noise N level of -21.2 dBm is obtained at a Raman gain target of 12 dB.

[0083] Figure 10B is a chart for explaining WDMLOS and the determination of the wavelength number reference value. The horizontal axis of Figure 10B is the number of wavelengths of the main signal, and the vertical axis is the optical power. In Figure 10B, the characteristics of the main signal received power (minimum) S are indicated by circles. The Raman noise + main signal received power characteristics SN are also indicated by squares.

[0084] Under the system operating conditions shown in FIG. 10B, the fiber type of the transmission line 101 is SMF, the Raman gain target is 12 dB, and the minimum reception target level of the main signal is −29 dBm.

[0085] Regarding the reference value of the number of wavelengths, the WDMLOS detection threshold Th is set to a value of −18.2 dBm, which is 3 dB larger than the power of the Raman noise N shown in FIG. 10A, “−21.2 dBm,” as a margin α. The number of wavelengths at which the main signal reception power S exceeds the WDMLOS detection threshold Th is set as the reference value (reference number of wavelengths).

[0086] In FIG. 10B, the margin α is a margin (for example, 3 dB) for the variation in the power of Raman noise N caused by the fiber characteristics of the transmission line 101, as described above. Also, the margin β is a margin (for example, 3 dB) for the variation in the main signal reception power S caused by level deviation between wavelengths due to optical level control, etc. In the example of FIG. 10B, for the power of Raman noise N of "-21.2 dBm," the margin α+β is set to a reference wavelength number of 24 from the intersection with the main signal reception power S. Also, in FIG. 10B, the main signal reception power S can also be used as the reference power.

[0087] The WDMLOS detection threshold Th and the reference wavelength number (and reference power) take different values ​​depending on the following parameters 1 to 4. 1. Optical wavelength band of the transmission system (C-band / L-band) 2. Fiber type of transmission line 101 3. Raman gain target of Raman amplifier 111 4.Minimum receiving target for main signal

[0088] (Example of APSD judgment conditions) 11 is a table showing an example of setting the APSD judgment conditions. APSD judgment condition setting information 1100 shown in FIG.

[0089] The APSD judgment condition setting information 1100 includes the number of wavelengths for each combination of the parameters 1 to 4 above, the WDMLOS detection threshold Th, and the APSD judgment condition. The number of wavelengths is divided into two groups based on the number of wavelengths in operation relative to the reference number of wavelengths. However, the number of wavelengths may also be divided based on the magnitude of the reference power of the main signal.

[0090] For example, for 1. the optical wavelength band of the transmission system "C-band" and 2. the fiber type of the transmission path 101 "SMF," 3. the Raman gain target "11" dB and 4. the minimum reception target of the main signal "-29 dBm" are set. Corresponding to these four parameters, when the number of connected wavelengths is "12 or more," the WDMLOS detection threshold Th is set to "-18.6" dBm and the APSD judgment condition is set to "WDMLOS & OSC loss." Furthermore, when the number of wavelengths is "11 or less," the WDMLOS detection threshold Th is set to "-39.2" dBm and the APSD judgment condition is set to "OSC loss."

[0091] Additionally, for 1. the optical wavelength band of the transmission system, "C-band," and 2. the fiber type of the transmission line 101, "DSF," 3. the Raman gain target, "9.6" dB, and 4. the minimum reception target of the main signal, "-29 dBm," are set. DSF stands for Dispersion Shifted Fiber. Corresponding to these four parameters, when the number of connected wavelengths is "39 ​​or more," the WDMLOS detection threshold Th is set to "-18.6" dBm, and the APSD judgment condition is set to "WDMLOS & OSC loss." Furthermore, when the number of wavelengths is "38 or less," the WDMLOS detection threshold Th is set to "-33.4" dBm, and the APSD judgment condition is set to "OSC loss."

[0092] Additionally, for 1. the optical wavelength band of the transmission system "L-band" and 2. the fiber type of the transmission line 101 "SMF," 3. the Raman gain target "11" dB and 4. the minimum reception target of the main signal "-27 dBm" are set. Corresponding to these four parameters, when the number of connected wavelengths is "4 or more," the WDMLOS detection threshold Th is set to "-21.5" dBm and the APSD judgment condition is set to "WDMLOS & OSC lost." Furthermore, when the number of wavelengths is "3 or less," the WDMLOS detection threshold Th is set to "-39.2" dBm and the APSD judgment condition is set to "OSC lost."

[0093] In addition, 1. the optical wavelength band of the transmission system is "L-band", 2. the fiber type of the transmission line 101 is "DSF", 3. the Raman gain target is "9.6" dB, 4. the minimum receiving power of the main signal is The target signal level is set to -27 dBm. Corresponding to these four parameters, when the number of connected wavelengths is four or more, the WDMLOS detection threshold Th is set to -21.5 dBm and the APSD judgment condition is set to WDMLOS & OSC loss. When the number of connected wavelengths is three or less, the WDMLOS detection threshold Th is set to -33.4 dBm and the APSD judgment condition is set to OSC loss.

[0094] The APSD control unit 605 accesses the monitoring unit 603, the setting information 616, and the APSD judgment condition database 615. Then, the APSD control unit 605 reads out setting information corresponding to the above parameters 1 to 4 during operation of the transmission system from the APSD judgment condition setting information 1100, and determines the WDMLOS detection threshold Th and APSD judgment conditions for each number of wavelengths.

[0095] (Example of overall processing for APSD control) 12 is a flowchart showing an example of the overall process of APSD control performed by the Raman amplifier. The process in Fig. 12 shows the overall process related to APSD control executed by each function (processor 701 in Fig. 7) of the Raman amplifier 100 shown in Fig. 6.

[0096] First, the Raman amplifier 100 monitors the main signal transmitted on the transmission path 101a (step S1201). Next, the Raman amplifier 100 determines whether the current device settings (setting information 616) exceed a predetermined condition (step S1202). For example, in wavelength number control, it determines whether the number of wavelengths in the current device settings (setting information 616) is greater than a reference wavelength number. In power control, it determines whether the total power of the main signal calculated from the current device settings (setting information 616) is greater than a reference power.

[0097] In controlling the number of wavelengths, if the determination result in step S1202 is that the number of wavelengths set in the device is greater than the reference number of wavelengths (step S1202: Yes), the Raman amplifier 100 proceeds to processing in step S1203. On the other hand, if the number of wavelengths set in the device is not greater than the reference number of wavelengths (step S1202: No), the Raman amplifier 100 proceeds to processing in step S1209.

[0098] In power control, if the determination result in step S1202 is that the total power of the main signal calculated from the device settings is greater than the reference power (step S1202: Yes), the Raman amplifier 100 proceeds to processing in step S1203. On the other hand, if the total power of the main signal calculated from the device settings is less than the reference power (step S1202: No), the Raman amplifier 100 proceeds to processing in step S1209.

[0099] In step S1203, the Raman amplifier 100 determines whether the monitoring result exceeds a predetermined condition (step S1203). For example, in wavelength number control, the Raman amplifier 100 determines whether the number of received wavelengths is greater than the reference number of wavelengths (step S1203). If the determination result shows that the number of received wavelengths is greater than the reference number of wavelengths (step S1203: Yes), the Raman amplifier 100 proceeds to processing in step S1204. On the other hand, if the number of received wavelengths is not greater than the reference number of wavelengths (step S1203: No), the Raman amplifier 100 proceeds to processing in step S1209.

[0100] In power control, the Raman amplifier 100 determines whether the total power of the received main signals is greater than the reference power (step S1203). If the determination result shows that the total power of the main signals is greater than the reference power (step S1203: Yes), the Raman amplifier 100 proceeds to processing in step S1204. On the other hand, if the total power of the main signals is not greater than the reference power (step S1203: No), the Raman amplifier 100 proceeds to processing in step S1209.

[0101] In step S1204, the Raman amplifier 100 switches the WDMLOS detection threshold Th (step S1204). In this switching, the Raman amplifier 100 refers to the APSD determination condition setting information 1100 and changes the setting of the WDMLOS detection threshold Th to the number of communicated wavelengths or the main signal power based on the above four parameters 1 to 4.

[0102] Next, the Raman amplifier 100 sets the APSD determination condition to OSC OFF & WDMLOS (step S1205).

[0103] Thereafter, the Raman amplifier 100 determines whether or not WDMLOS has been detected (step S1206). If the determination result shows that WDMLOS has been detected (step S1206: Yes), the Raman amplifier 100 proceeds to the process of step S1207. On the other hand, if WDMLOS has not been detected (step S1206: No), the Raman amplifier 100 returns to the process of step S1201.

[0104] In step S1207, the Raman amplifier 100 determines whether an OSC interruption has been detected (step S1207). If the determination result indicates that an OSC interruption has been detected (step S1207: Yes), the Raman amplifier 100 proceeds to step S1208. On the other hand, if a WDMLOS has not been detected (step S1207: No), the Raman amplifier 100 returns to step S1201.

[0105] In step S1209, the Raman amplifier 100 sets the APSD determination condition to OSC interruption (step S1209).

[0106] Thereafter, the Raman amplifier 100 determines whether or not an OSC linkdown has been detected (step S1210). If an OSC linkdown has been detected (step S1210: Yes), the Raman amplifier 100 proceeds to the process of step S1208. On the other hand, if an OSC linkdown has not been detected (step S1210: No), the Raman amplifier 100 returns to the process of step S1201.

[0107] In step S1208, the Raman amplifier 100 executes control related to APSD based on the APSD determination condition determined in step S1205 or step S1209 (step S1208).

[0108] The Raman amplifier according to the embodiment described above, which Raman amplifies an optical signal on a transmission line by Raman pumping, monitors a main signal that is operating as an optical signal and switches a WDMLOS detection threshold for determining whether to output a WDMLOS alarm when a transmission line is disconnected, based on the monitoring result of the main signal. If the monitoring result of the main signal that is operating exceeds a predetermined condition, APSD determination is made using APSD determination condition 1 based on an integration of OSC disconnection and WDMLOS. On the other hand, if the monitoring result of the main signal that is operating falls below the predetermined condition, APSD determination is made using APSD determination condition 2 based on OSC disconnection. For example, the monitoring may be made on the power of the main signal that is operating, in which case the predetermined condition is a predetermined reference power. The monitoring may also be made on the number of wavelengths of the main signal that is operating, in which case the predetermined condition is a predetermined reference number of wavelengths. Furthermore, the monitoring may be made on the power of the main signal that is operating, in which case the power of the main signal that is operating may be replaced with the corresponding number of wavelengths, and the predetermined condition may be a predetermined reference number of wavelengths. As a result, particularly in a Raman amplifier that performs backward Raman pumping, the device is affected by Raman noise due to backward pumping when the fiber in the transmission path is cut. However, according to the embodiment, it is possible to prevent APSD from being applied when an OSC cut occurs while the main signal is communicating, thereby making it possible to avoid unexpected cuts in the main signal.

[0109] Furthermore, the Raman amplifier may determine the number of wavelengths of the main signal being transmitted under certain signal power conditions, and under other conditions, count one signal as a number of wavelengths other than 1. This allows the method of counting the number of wavelengths when performing APSD control based on the number of wavelengths to accommodate fluctuating main signal power.

[0110] Furthermore, the control unit of the Raman amplifier sets the WDMLOS detection threshold to a second set value, for example, an initial set reference value, when the power of the transmitted main signal is lower than the reference power or when the number of wavelengths of the transmitted main signal is lower than the reference number of wavelengths. The control unit of the Raman amplifier sets the WDMLOS detection threshold to a first set value when the power of the transmitted main signal is higher than the reference power or when the number of wavelengths of the transmitted main signal is higher than the reference number of wavelengths. For example, the first set value is higher than the reference value and different from the second set value. This allows the WDMLOS detection threshold to be set to an appropriate value corresponding to fluctuations in the power or number of wavelengths of the main signal, enabling more accurate APSD control.

[0111] Furthermore, the Raman amplifier may use a reference power or a reference number of wavelengths that is set based on the fiber type of the transmission line, the Raman noise power of the Raman amplification, and the Raman amplification gain, so that the received power of the transmitted main signal is greater than the Raman noise power. Based on these various parameters, the number of wavelengths of the transmitted main signal can be correctly monitored using the reference power or reference number of wavelengths applied to the operating system.

[0112] Furthermore, the Raman amplifier may use a WDMLOS detection threshold set based on one or a combination of the following: the wavelength band of the transmission line, the fiber type of the transmission line, the noise power of the Raman amplification, and the received power of the main signal. Based on these various parameters, the WDMLOS detection threshold applied to the operating system can accurately determine whether or not WDMLOS output is present.

[0113] The control unit of the Raman amplifier may also be capable of setting the WDMLOS detection threshold according to the power or number of wavelengths of the transmitted main signal. For example, the WDMLOS detection threshold may be variably set according to the power or number of wavelengths of the transmitted main signal. Alternatively, as a fixed value, when the power of the transmitted main signal is greater than a reference power or when the number of wavelengths of the main signal is greater than the reference number of wavelengths, the WDMLOS detection threshold may be set to a first setting value, APSD determination may be performed according to APSD determination condition 1, and APSD control may not be performed when the main signal is connected and an OSC is interrupted. This makes it possible to suppress APSD and avoid main signal interruption even if an OSC interruption occurs while the main signal is connected.

[0114] Furthermore, if the power of the transmitted main signal is less than the reference power or the number of wavelengths of the main signal is less than the reference number of wavelengths, the control unit of the Raman amplifier sets the WDMLOS detection threshold to a second set value, performs APSD judgment under APSD judgment condition 2, and performs APSD control when OSC is interrupted. This makes it possible to perform appropriate APSD control when OSC interruption occurs when the power of the transmitted main signal is less than the reference power or the number of wavelengths of the main signal is less than the reference number of wavelengths.

[0115] The following additional notes are provided regarding the above-described embodiment.

[0116] (Appendix 1) A Raman amplifier that amplifies an optical signal on a transmission line by Raman pumping, monitor a main signal transmitted by the optical signal; Switching a WDMLOS detection threshold for determining whether or not to output an alarm (WDMLOS) when a transmission line is disconnected according to the monitoring result of the main signal; If the monitoring result of the main signal being communicated exceeds a predetermined condition, the presence or absence of APSD (Auto Power Shut Down) control is determined using APSD (Auto Power Shut Down) determination condition 1 based on the OSC (Optical Supervisory Channel) disconnection and the WDMLOS integration. If the monitoring result of the main signal that is being communicated falls below a predetermined condition, the presence or absence of APSD control is determined using the APSD determination condition 2 due to OSC interruption. A Raman amplifier comprising a control unit.

[0117] (Supplementary Note 2) The monitoring is monitoring the power of the main signal being transmitted, 2. The Raman amplifier according to claim 1, wherein the predetermined condition is a predetermined reference power.

[0118] (Supplementary Note 3) The monitoring is monitoring the number of wavelengths of the main signal that are being communicated, 2. The Raman amplifier according to claim 1, wherein the predetermined condition is a predetermined reference wavelength number.

[0119] (Supplementary Note 4) The monitoring is monitoring the power of the main signal being transmitted, The power of the transmitted main signal is replaced with the corresponding number of wavelengths; 2. The Raman amplifier according to claim 1, wherein the predetermined condition is a predetermined reference wavelength number.

[0120] (Appendix 5) A Raman amplifier according to appendix 4, characterized in that the number of wavelengths of the main signal being communicated is determined under certain signal power conditions, and under other conditions, one signal is counted as a number of wavelengths other than one wave.

[0121] (Supplementary Note 6) The control unit 3. The Raman amplifier according to claim 2, wherein the WDMLOS detection threshold can be set according to the power of the main signal being transmitted.

[0122] (Supplementary Note 7) The control unit 4. The Raman amplifier according to claim 3, wherein the WDMLOS detection threshold can be set according to the number of wavelengths of the main signal being transmitted.

[0123] (Appendix 8) The Raman amplifier device according to appendix 2, characterized in that the reference power is set to a power at which the received power of the transmitted main signal is greater than the Raman noise power, based on the fiber type of the transmission path, the Raman noise power of the Raman amplification, and the Raman amplification gain.

[0124] (Appendix 9) The Raman amplifier according to appendix 3, characterized in that the reference wavelength number is set to a wavelength number at which the received power of the transmitted main signal becomes larger than the Raman noise power, based on the fiber type of the transmission path, the Raman noise power of the Raman amplification, and the Raman amplification gain.

[0125] (Appendix 10) The Raman amplification device according to appendix 1, characterized in that the WDMLOS detection threshold is set to a value based on one or a combination of a wavelength band of the transmission line, a fiber type of the transmission line, noise power of the Raman amplification, and received power of the main signal.

[0126] (Supplementary Note 11) The control unit If the power of the main signal being communicated is greater than the reference power, the WDMLOS detection threshold is set to a first set value, and APSD determination is performed according to the APSD determination condition 1; When the main signal is in a communication state and the OSC is disconnected, the APSD control is not performed. 3. The Raman amplifier according to claim 2,

[0127] (Supplementary Note 12) The control unit If the number of wavelengths of the main signal that are communicated is greater than the reference number of wavelengths, the WDMLOS detection threshold is set to a first set value, and APSD determination is performed according to the APSD determination condition 1; When the main signal is in a communication state and the OSC is disconnected, the APSD control is not performed. 4. The Raman amplifier according to claim 3,

[0128] (Supplementary Note 13) The control unit If the power of the main signal being communicated is less than the reference power, the WDMLOS detection threshold is set to a second set value, and APSD determination is performed according to the APSD determination condition 2; When the OSC is cut off, the APSD control is performed. 3. The Raman amplifier according to claim 2,

[0129] (Supplementary Note 14) The control unit If the number of wavelengths of the main signal that are communicated is smaller than the reference number of wavelengths, the WDMLOS detection threshold is set to a second set value, and APSD determination is performed according to the APSD determination condition 2; When the OSC is cut off, the APSD control is performed. 4. The Raman amplifier according to claim 3,

[0130] (Appendix 15) A Raman amplification method for a Raman amplifier that amplifies an optical signal in a transmission line by Raman pumping, comprising: monitor a main signal transmitted by the optical signal; Switching a WDMLOS detection threshold for determining whether or not to output an alarm (WDMLOS) when a transmission line is disconnected according to the monitoring result of the main signal; If the monitoring result of the main signal being communicated exceeds a predetermined condition, the presence or absence of APSD (Auto Power Shut Down) control is determined using APSD (Auto Power Shut Down) determination condition 1 based on the OSC (Optical Supervisory Channel) disconnection and the WDMLOS integration. If the monitoring result of the main signal that is being communicated falls below a predetermined condition, the presence or absence of APSD control is determined using the APSD determination condition 2 due to OSC interruption. A Raman amplification method comprising:

[0131] (Supplementary Note 16) The monitoring is monitoring the power of the main signal being transmitted, 16. The Raman amplification method according to claim 15, wherein the predetermined condition is a predetermined reference power.

[0132] (Supplementary Note 17) The monitoring is monitoring the number of wavelengths of the main signal that are being communicated, 16. The Raman amplification method according to claim 15, wherein the predetermined condition is a predetermined reference wavelength number.

[0133] (Supplementary Note 18) The monitoring is monitoring the power of the main signal being transmitted, The power of the main signal being transmitted is replaced with the corresponding number of wavelengths, and the reference power is replaced with a predetermined reference number of wavelengths; 16. The Raman amplification method according to claim 15, wherein the predetermined condition is a predetermined reference wavelength number. [Explanation of symbols]

[0134] 100(100A, 100B) Raman amplifier 101(101a, 101b) Transmission line 111 Raman amplifier 121(121a,121b) Multiplexer / demultiplexer 123(123a,123b) Optical amplifier 125a multiplexer 126 OSC optical transceiver 601 Main signal receiver 602 WDMLOS detector 603 Monitoring Department 604 WDMLOS detection threshold switching unit 605 APSD Control Unit 606 WDM optical transmitter 615 APSD Judgment Condition Database 616 Setting Information 701 processor 702 memory 705 Recording Media 1100 APSD judgment condition setting information N Raman noise power S Main signal reception power Th WDMLOS detection threshold

Claims

1. In a Raman amplifier that Raman amplifies an optical signal on a transmission line by Raman pumping, monitoring a main signal transmitted by said optical signal; Switching a WDMLOS detection threshold for determining whether or not an alarm (WDMLOS) is output when a transmission line is cut off according to a result of monitoring the main signal; When the monitoring result of the main signal that is being communicated exceeds a predetermined condition, the presence or absence of APSD control is judged using APSD (Auto Power Shut Down) judgment condition 1 based on an OSC (Optical Supervisory Channel) cutoff and an integration of WDMLOS; When the monitoring result of the main signal being communicated falls below a predetermined condition, the presence or absence of APSD control is determined using the APSD determination condition 2 due to OSC interruption. A Raman amplifier comprising a control unit.

2. The monitoring is monitoring the power of the main signal being transmitted, 2. The Raman amplifier according to claim 1, wherein the predetermined condition is a predetermined reference power.

3. The monitoring is monitoring the number of wavelengths of the main signal that are being communicated, 2. The Raman amplifier according to claim 1, wherein the predetermined condition is a predetermined reference wavelength number.

4. The monitoring is monitoring the power of the main signal being transmitted, The power of the main signal being transmitted is replaced with the corresponding number of wavelengths, 2. The Raman amplifier according to claim 1, wherein the predetermined condition is a predetermined reference wavelength number.

5. 5. The Raman amplifier according to claim 4, wherein the number of wavelengths of the main signal that are in communication is determined under certain signal power conditions, and under other conditions, one signal is counted by a number of wavelengths other than one.

6. The control unit is 3. The Raman amplifier according to claim 2, wherein the WDMLOS detection threshold can be set according to the power of the transmitted main signal.

7. The control unit is 4. The Raman amplifier according to claim 3, wherein the WDMLOS detection threshold can be set in accordance with the number of wavelengths of the main signal that are communicated.

8. 3. The Raman amplifier according to claim 2, wherein the reference power is set to a power at which the received power of the main signal being transmitted is greater than the Raman noise power, based on a fiber type of the transmission line, the Raman noise power of the Raman amplification, and the Raman amplification gain.

9. 4. The Raman amplifier according to claim 3, wherein the reference wavelength number is set to a number of wavelengths at which the received power of the transmitted main signal is greater than the Raman noise power, based on a fiber type of the transmission line, the Raman noise power of the Raman amplification, and the Raman amplification gain.

10. 2. The Raman amplifier according to claim 1, wherein the WDMLOS detection threshold is set to a value based on one or a combination of a wavelength band of the transmission line, a fiber type of the transmission line, noise power of the Raman amplification, and a reception power of the main signal.

11. The control unit is When the power of the main signal being communicated is greater than the reference power, the WDMLOS detection threshold is set to a first set value, and an APSD judgment is performed according to the APSD judgment condition 1; When the main signal is in a communication state and the OSC is cut off, the APSD control is not performed.

3. The Raman amplifier according to claim 2.

12. The control unit is When the number of wavelengths of the main signal that are communicated is greater than the reference number of wavelengths, the WDMLOS detection threshold is set to a first set value, and an APSD judgment is performed according to the APSD judgment condition 1; When the main signal is in a communication state and the OSC is cut off, the APSD control is not performed.

4. The Raman amplifier according to claim 3.

13. The control unit is When the power of the main signal being communicated is less than the reference power, the WDMLOS detection threshold is set to a second set value, and an APSD judgment is performed according to the APSD judgment condition 2; When the OSC is cut off, the APSD control is performed.

3. The Raman amplifier according to claim 2.

14. The control unit is When the number of wavelengths of the main signal that are communicated is smaller than the reference number of wavelengths, the WDMLOS detection threshold is set to a second set value, and an APSD judgment is performed according to the APSD judgment condition 2; When the OSC is cut off, the APSD control is performed.

4. The Raman amplifier according to claim 3.

15. A Raman amplification method for a Raman amplifier that Raman amplifies an optical signal in a transmission line by Raman pumping, comprising: monitoring a main signal transmitted by said optical signal; Switching a WDMLOS detection threshold for determining whether or not an alarm (WDMLOS) is output when a transmission line is cut off according to a result of monitoring the main signal; When the monitoring result of the main signal that is being communicated exceeds a predetermined condition, the presence or absence of APSD control is judged using APSD (Auto Power Shut Down) judgment condition 1 based on an OSC (Optical Supervisory Channel) cutoff and an integration of WDMLOS; When the monitoring result of the main signal being communicated falls below a predetermined condition, the presence or absence of APSD control is determined using the APSD determination condition 2 due to OSC interruption. A Raman amplification method comprising:

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