Optical transmission system and quality estimation method

Abstract

The objective is to provide an optical transmission system and quality estimation method for estimating the quality of signal light during actual operation, at locations other than the terminal station. [Solution] The optical transmission system includes: a first optical transmission device that transmits a first signal light in actual operation and a first pseudo-light having a different wavelength from the first signal light; a second optical transmission device that receives the first signal light and the first pseudo-light from the first optical transmission device; a measurement unit that measures the first quality of the first pseudo-light between the first optical transmission device and the second optical transmission device; and an estimation unit that estimates the second quality of the first signal light between the first optical transmission device and the second optical transmission device based on the first quality and an index value of wavelength dependence in the signal band.

Description

Technical Field

[0001] This invention relates to an optical transmission system and a quality estimation method.

Background Art

[0002] There is known an undersea optical communication system in which terminals communicate with each other by transmitting and receiving wavelength-division multiplexed optical signals via an undersea cable. It is also known to provide a transponder at a terminal (see, for example, Patent Document 1). The wavelength-division multiplexed optical signal output from the transmitting terminal includes an optical signal (main signal) with data addressed to the receiving terminal superimposed thereon, and dummy light inserted to compensate for the intensity of the wavelength-division multiplexed optical signal according to the presence or absence of the optical signal (see, for example, Patent Documents 2 and 3).

[0003] The dummy light includes a plurality of lights having arbitrary center wavelengths and arbitrary bandwidths. The dummy light source that outputs the dummy light includes, for example, an ASE (Amplified Spontaneous Emission) light source and a WSS (Wavelength Selective Switch) (see, for example, Patent Document 4). In addition, it is also known that one index of the quality of a signal transmitted in a WDM (Wavelength Division Multiplexing) optical communication system is the OSNR (Optical Signal-to-Noise Ratio) (see, for example, Patent Document 5).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

[0005] Incidentally, signal quality, such as OSNR, is sometimes measured by transponders during the actual operation of an optical network. Therefore, if transponders are installed at the terminal stations, the signal quality from one terminal station to the other is measured by the transponder. Multiple transmission nodes, such as ROADMs (Reconfigurable Optical Add / Drop Multiplexers), may be installed between the two terminal stations. However, even in such cases, only the signal quality between terminal stations is measured, and there is a problem in that the signal quality between transmission nodes is not measured for each transmission node during actual operation.

[0006] Therefore, one objective is to provide an optical transmission system and quality estimation method that estimates the quality of signal light during actual operation at locations other than the terminal station. [Means for solving the problem]

[0007] In one embodiment, the optical transmission system includes: a first optical transmission device that transmits a first signal light in actual operation and a first pseudo-light having a different wavelength from the first signal light; a second optical transmission device that receives the first signal light and the first pseudo-light from the first optical transmission device; a measurement unit that measures a first quality of the first pseudo-light between the first optical transmission device and the second optical transmission device; and an estimation unit that estimates a second quality of the first signal light between the first optical transmission device and the second optical transmission device based on the first quality and an index value of wavelength dependence in the signal band.

[0008] In one embodiment, the optical transmission system includes: a first optical transmission device that transmits a first signal light and a second signal light of different wavelengths, both of which are in actual operation; a second optical transmission device that receives the first signal light and the second signal light and transmits the first signal light and a plurality of pseudo-lights of wavelengths including the wavelengths of the second signal light; a third optical transmission device that receives the first signal light and the first pseudo-light from the second optical transmission device; a measurement unit that measures the first quality of the first pseudo-light between the second optical transmission device and the third optical transmission device; and an estimation unit that estimates the second quality of the first signal light between the first optical transmission device and the third optical transmission device based on the first quality and an index value of wavelength dependence in the signal band. [Effects of the Invention]

[0009] The quality of the signal light during actual operation can be estimated at locations other than the terminal station. [Brief explanation of the drawing]

[0010] [Figure 1] This is an example of an optical network. [Figure 2] (a) is an example of a spectral diagram of an inserted signal light. (b) is an example of a spectral diagram of a WDM light. (c) is an example of a spectral diagram of a branched signal light. [Figure 3] This is an example of the ROADM circuit configuration. [Figure 4] This is an example of the functional configuration of the control unit. [Figure 5] This is an example of an OSNR database. [Figure 6] This diagram illustrates an example of correction in the OSNR database. [Figure 7] This is an example of a corrected OSNR database. [Figure 8] This diagram illustrates Case #1, which describes a real-world operation of an optical network. [Figure 9] This is an example of estimating the OSNR of a signal light in Case #1. [Figure 10] This is another example of OSNR estimation for signal light in Case #1. [Figure 11] This is a diagram for explaining Case #2 during the actual operation of the optical network. [Figure 12] This is an example of estimating the OSNR of the signal light in Case #2. [Figure 13] This is another example of estimating the OSNR of the signal light in Case #2. [Figure 14] This is a diagram for explaining Case #3 during the actual operation of the optical network. [Figure 15] This is an example of estimating the OSNR of the signal light in Case #3. [Figure 16] This is another example of estimating the OSNR of the signal light in Case #3. [Figure 17] This is a flowchart showing an example of the operation of the ROADM. [Figure 18] This is a diagram comparing three comparative examples and an example of the implementation.

Mode for Carrying Out the Invention

[0011] Hereinafter, the mode for carrying out the present case will be described with reference to the drawings.

[0012] As shown in FIG. 1, the optical network NW includes a plurality of transponders (denoted as TRPN in FIG. 1) 10 and 20, and a plurality of ROADMs 40S, 40X, 40Y, ···, 40J, 40G. The transponders 10 and 20 are transceiver nodes provided at the terminal stations of the optical network NW.

[0013] The ROADMs 40S, 40X, 40Y, ···, 40J, 40G are all transmission nodes provided at non-terminal stations (such as relay stations or switching stations, etc.) excluding the terminal stations from the optical network NW. The ROADM 40S is an example of the first optical transmission device. At least one of the ROADMs 40X, 40Y, ···, 40J is an example of the second optical transmission device. The ROADM 40G is an example of the third optical transmission device. At least one of the ROADMs 40X, 40Y, ···, 40J may be the third optical transmission device, and the ROADM 40G may be the second optical transmission device.

[0014] Transponder 10 and ROADM40S are connected to each other by transmission line 30. ROADM40S and 40X are connected to each other by transmission line 31. ROADM40X and 40Y are connected to each other by transmission line 32. ROADM40J and 40G are connected to each other by transmission line 33. ROADM40G and transponder 20 are connected to each other by transmission line 34.

[0015] Transmission lines 30, 31, 32, 33, and 34 all contain optical fibers. Relay nodes such as ILA (Optical In-Line Amplifier Equipment) may be installed in the middle of each of the transmission lines 31, 32, and 33. Note that ROADM40Y and 40J are connected in the same way as ROADM40S and 40X, but are omitted in Figure 1. One or more ROADMs or ILAs (not shown) may be installed between ROADM40Y and 40J via the transmission line.

[0016] Transponder 10 comprises an optical transmitter (labeled Tx in Figure 1) 11 and an optical receiver (labeled Rx in Figure 1) 12. Transponder 20 comprises an optical transmitter 21 and an optical receiver 22. Optical transmitter 11 transmits signal light L1. Signal light L1 is input to the transmission path 30, propagates through the transmission path 30, and reaches ROADM 40S.

[0017] For example, when the optical power of a signal light L1 with wavelength λ1 belonging to the C-band (Conventional-band) is measured at the first measurement point P1 on the transmission line 30, the optical power of the signal light L1 with wavelength λ1 appears alone in the spectral diagram, as shown in Figure 2(a).

[0018] As shown in Figure 1, the ROADM40S outputs WDM light Lw1, which is obtained by combining signal light L1 and dummy light (pseudo-light) Ld. In the ROADM40S, as shown in Figure 2(b), not only dummy light Ld wavelengths λp1, λp2, etc., belonging to the C band, but also dummy light Ld wavelengths λp3, λp4, λp5, etc., belonging to the L band (Long-wavelength-band), are combined. In the ROADM40S, signal light L1 is inserted (added) into the empty wavelength λ1 among these dummy light Ld. In this embodiment, the ROADM40S into which signal light L1 is inserted corresponds to the starting point of signal light L1.

[0019] As shown in Figure 1, the WDM light Lw1 output from ROADM40S is input to the transmission path 31, propagates along the transmission path 31, and reaches the first ROADM40X installed after ROADM40S. Therefore, when the optical power of WDM light Lw1 is measured at the second measurement point P2 on the transmission path 31, as shown in Figure 2(b), the spectral diagram shows the optical power of the signal light L1 with wavelength λ1 and the optical power of dummy light Ld with wavelengths λp1, λp2, λp3, λp4, λp5, etc. In this way, the dummy light Ld fills the empty bandwidths in the signal bands such as the C band and L band used in the actual operation of the optical network NW, excluding the wavelength λ1 of the signal light L1.

[0020] As shown in Figure 1, ROADM40X forwards WDM optical signal Lw1 from ROADM40S to ROADM40Y, which is the second unit installed. Similarly, ROADM40Y forwards WDM optical signal Lw1 from ROADM40S to ROADM40J, which is the Jth unit installed. ROADM40J forwards WDM optical signal Lw1 to ROADM40G.

[0021] ROADM40G separates the signal light L1 from the WDM light Lw1 and outputs it to the transmission path 34. The signal light L1 propagates along the transmission path 34 and reaches the transponder 20. As a result, the optical receiver 22 of the transponder 20 receives the signal light L1. In this embodiment, ROADM40G, which branches (drops) the signal light L1 from the WDM light Lw1, corresponds to the destination of the signal light L1. When the optical power of the signal light L1 with wavelength λ1 is measured at the third measurement point P3 on the transmission path 34, the optical power of the signal light L1 with wavelength λ1 appears alone in the spectral diagram, as shown in Figure 2(c).

[0022] ROADM40S, 40X, 40Y, ..., 40J, and 40G are all electrically connected to an NMS (Network Management System) 80. The NMS 80 controls the operation of ROADM40S and other devices via a communication network 81 such as a LAN (Local Area Network) or the Internet. The NMS 80 includes an optical network controller, which can control the operation of ROADM40S and other devices. The NMS 80 or optical network controller is an example of a control device. As will be described in detail later, the NMS 80 manages the wavelength arrangement and various measured values ​​of signal light L1 and dummy light Ld, and estimates the OSNR of signal light L1 as the quality of signal light L1 based on the wavelength arrangement and various measured values.

[0023] The optical transmission system may be implemented using ROADM40S, 40X, 40Y, ..., 40J, 40G excluding NMS80, or it may be implemented using NMS80 and ROADM40S, 40X, ..., 40Y, 40J, 40G.

[0024] The circuit configuration of ROADM40S will be explained with reference to Figure 3. Note that ROADM40X, 40Y, ..., 40J, and 40G have basically the same circuit configuration as ROADM40S, so detailed explanations will be omitted. In Figure 3, the symbols necessary for explaining ROADM40G are shown in parentheses.

[0025] The ROADM40S comprises an OSC (Optical Supervisory Channel) optical receiver (indicated as OSC Rx in Figure 3) 41, an OSC optical transmitter (indicated as OSC Tx in Figure 3) 42, and a PD (Photo Diode) 43. The ROADM40S also includes an OCM (Optical Channel Monitor) 44, optical amplifiers 45 and 46, and an MCS (Multicast Switch) 47. Furthermore, the ROADM40S includes WSS (Wavelength Selective Switch) 48 and 49, an ASE (Amplified Spontaneous Emission) light source (simply referred to as ASE in Figure 3) 50, and a control unit 100. Details of the control unit 100 will be described later.

[0026] The OSC optical transmitter 42 transmits OSC optical Lo1 based on instructions from the control unit 100. OSC optical Lo1 is output to the transmission path 31 via the WDM coupler 54. In other words, ROADM40S outputs OSC optical Lo1 to the transmission path 31. The transmission path 31 is connected to ROADM40X (see Figure 1). Therefore, OSC optical Lo1 reaches ROADM40X.

[0027] Similarly, the OSC optical Lo2 output from ROADM40J reaches ROADM40G via the transmission path 33. The OSC optical receiver 41 receives the OSC optical Lo2 via the branch coupler 51. Upon receiving the OSC optical Lo2, the OSC optical receiver 41 measures the optical power of the received OSC optical Lo2 and notifies the control unit 100 of the measured value.

[0028] PD43 detects the WDM light Lw1 output from ROADM40J and branched by the branch coupler 52. The branch coupler 52 is positioned before or upstream of the optical amplifier 45. This allows PD43 to detect the WDM light Lw1 before it is input to ROADM40G and then to the optical amplifier 45. When PD43 detects the WDM light Lw1, it notifies the control unit 100 of the detected value of the WDM light Lw1.

[0029] The OCM44 measures the optical power of the WDM light Lw1, which is output from the ROADM40J and branched by the branch coupler 53, for each wavelength. The branch coupler 53 is located after or downstream of the optical amplifier 45. This allows the OCM44 to measure the optical power of the WDM light Lw1 for each wavelength after it has passed through the optical amplifier 45. In other words, the OCM44 can measure the optical power of the signal light L1 and the dummy light Ld for each wavelength. After measuring the optical power of the signal light L1 and the dummy light Ld, the OCM44 notifies the control unit 100 of the measured value for the dummy light Ld.

[0030] Optical amplifier 45 amplifies the optical power of WDM optical Lw1 output from ROADM40J and input to ROADM40G. Optical amplifier 46 amplifies the optical power of WDM optical Lw1 output from ROADM40S toward ROADM40X.

[0031] When the signal light L1 is input to the MCS47, it detects the wavelength λ1 of the signal light L1 and notifies the control unit 100. Also, when the signal light L1 is input to the MCS47, based on instructions from the control unit 100, it selects a path to output the signal light L1 and outputs the signal light L1 to the selected path. For example, when the signal light L1 transmitted from the optical transmitter 11 and propagated through the transmission path 30 is input to the MCS47, it selects WSS49 from the WSS48 and 49 which are optically connected to the MCS47. When the signal light L1 output from WSS48 is input to the MCS47, it selects the transmission path 34 which is optically connected to the optical receiver 22.

[0032] The WSS48 includes a demultiplexer that separates the WDM light Lw1 into individual wavelengths. When the WDM light Lw1 is input to the WSS48, it separates the WDM light Lw1 into individual wavelengths and outputs the signal light L1 contained in the WDM light Lw1 to the MCS47 based on instructions from the control unit 100. The WSS48 can also block the transmission of dummy light Ld contained in the WDM light Lw1.

[0033] The WSS49 includes a multiplexer that combines the signal light L1 and the dummy light Ld. When the signal light L1 is input to the WSS49, based on instructions from the control unit 100, it outputs WDM light Lw1, which is the combined signal light L1 and the dummy light Ld, to the optical amplifier 46. The ASE light source 50 switches between emitting and stopping emission based on instructions from the control unit 100, and for example, when emitting light, it outputs dummy light Ld with a wavelength excluding the wavelength λ1 of the signal light L1. The dummy light Ld output from the ASE light source 50 is input to the WSS49. As a result, the WSS49 can output WDM light Lw1, which is the combined signal light L1 and the dummy light Ld.

[0034] The hardware and functional configuration of the control unit 100 will be described with reference to Figures 4 to 7.

[0035] The control unit 100 is implemented by a processor such as a CPU (Central Processing Unit) and memory such as RAM (Random Access Memory) and ROM (Read Only Memory). The control program stored in ROM is temporarily stored in RAM by the CPU. By executing the stored control program, the CPU implements various functions described later. The control program should conform to the flowchart described later. The control unit 100 may also be implemented by hardware circuits such as FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit).

[0036] As shown in Figure 4, the control unit 100 includes a storage unit 110, an arithmetic unit 120, an input unit 130, and an output unit 140. The storage unit 110 can be implemented by the memory described above. The arithmetic unit 120 can be implemented by the processor described above. The input unit 130 and the output unit 140 can be implemented by a communication interface (I / F).

[0037] The memory unit 110, the calculation unit 120, the input unit 130, and the output unit 140 are connected to each other. The memory unit 110 includes a first wavelength memory unit 111, a second wavelength memory unit 112, a measurement value memory unit 113, a first quality index memory unit 114, a second quality index memory unit 115, and a second quality memory unit 116. The calculation unit 120 includes a first wavelength detection unit 121, a second wavelength detection unit 122, a span loss measurement unit 123, and an input optical power measurement unit 124. The calculation unit 120 also includes a first quality measurement unit 125, a correction unit 126, a second quality estimation unit 127, and a second quality notification unit 128. The span loss measurement unit 123, the input optical power measurement unit 124, and the first quality measurement unit 125 are examples of measurement units. The second quality estimation unit 127 is an example of an estimation unit.

[0038] The first wavelength detection unit 121 detects the wavelength λ1 of the signal light L1 to be inserted, which is input to the WSS49 (see Figure 3), and the wavelengths λp1, ..., λp5, etc., of the dummy light Ld associated with the signal light L1 to be inserted. When the first wavelength detection unit 121 detects wavelength λ1 and wavelengths λp1, ..., λp5, etc., it stores wavelength λ1 and wavelengths λp1, ..., λp5, etc., in the first wavelength storage unit 111.

[0039] The first wavelength storage unit 111 stores the wavelength λ1 and the wavelengths λp1, ..., λp5, etc., as post-wavelength data. The NMS 80 accesses the first wavelength storage unit 111 periodically or irregularly to acquire the post-wavelength data. Once the NMS 80 acquires the post-wavelength data, it manages the post-wavelength data.

[0040] The second wavelength detection unit 122 detects the wavelength λ1 of the signal light L1 to be branched, which is included in the WDM light Lw1 input to the WSS48 (see Figure 3), and the wavelengths λp1, ..., λp5, etc., of the dummy light Ld included in the WDM light Lw1. When the second wavelength detection unit 122 detects wavelengths λ1 and λp1, ..., λp5, etc., it stores the wavelengths λ1 and λp1, ..., λp5, etc., in the second wavelength storage unit 112.

[0041] The second wavelength storage unit 112 stores pre-wavelength data by associating wavelength λ1 with wavelengths λp1, ..., λp5, etc. The NMS 80 accesses the second wavelength storage unit 112 periodically or irregularly to acquire the pre-wavelength data. Once the NMS 80 acquires the pre-wavelength data, it manages the pre-wavelength data.

[0042] The span loss measurement unit 123 measures the span loss between ROADM 40S and 40G based on the set value of the optical power of OSC optical Lo2 transmitted by the OSC optical transmission unit 42 and the measured value of the optical power of OSC optical Lo2 notified by the OSC optical reception unit 41. Once the span loss measurement unit 123 has measured the span loss, it stores the measured value in the measured value storage unit 113.

[0043] The input optical power measurement unit 124 measures the input optical power of the WDM optical Lw1 input to the optical amplifier 45 based on the detected value of the WDM optical Lw1 notified from the PD43. After measuring the input optical power, the input optical power measurement unit 124 stores the measured value of the input optical power in the measured value storage unit 113.

[0044] The first quality measurement unit 125 measures the OSNR of the dummy light Ld as the quality of the dummy light Ld based on the optical power measurement by the OCM44 when the dummy light Ld is emitting light and the optical power measurement by the OCM44 when the dummy light Ld stops emitting light. In other words, the OSNR of the dummy light Ld is an example of the first quality. When the first quality measurement unit 125 measures the OSNR of the dummy light Ld, it stores the measured value of the OSNR in the measured value storage unit 113.

[0045] As a result, the measurement value storage unit 113 stores the measured span loss, the measured input optical power, and the measured OSNR of the dummy optical Ld as measurement data. The NMS 80 accesses the measurement value storage unit 113 periodically or irregularly to acquire the measurement data. Once the NMS 80 acquires the measurement data, it manages the measurement data.

[0046] The first quality index storage unit 114 stores the OSNR database. The OSNR database is created in advance (for example, before shipment or before operation). The OSNR database may also be created before the start of operation of the optical communication service performed between ROADM40S and 40G based on the signal light L1. As shown in Figure 5, the OSNR database records wavelength-dependent OSNR index values ​​in signal bands such as the C band and L band for each span loss at all wavelengths including the wavelength λ1 of the signal light L1 and the wavelengths λp1, ..., λp5 of the dummy light Ld. As an example, Figure 5 shows a first OSNR index value 85 with a span loss of 10 dB, a second OSNR index value 86 with a span loss of 20 dB, and a third OSNR index value 87 with a span loss of 30 dB. The number of OSNR index values ​​may be increased or decreased by changing the unit interval of span loss, which is 10 dB.

[0047] The correction unit 126 corrects the OSNR database based on the span loss measurement value stored in the measurement value storage unit 113. For example, as shown in Figure 6, if the measurement value storage unit 113 stores 25 dB as the span loss measurement value, the correction unit 126 corrects the second OSNR index value 86 and the third OSNR index value 87 to the new OSNR index value 90 based on this measurement value. The correction unit 126 may correct both the second OSNR index value 86 and the third OSNR index value 87, or it may correct either one of them.

[0048] For example, the correction unit 126 can generate a new OSNR index value 90 with a span loss of 25 dB by calculating the average of a second OSNR index value 86 with a span loss of 20 dB and a third OSNR index value 87 with a span loss of 30 dB. If the measured span loss is 22 dB or 28 dB, the correction unit 126 may change the correction ratio of the second OSNR index value 86 and the third OSNR index value 87 based on these measured values.

[0049] When the correction unit 126 corrects the OSNR database, it stores the new OSNR index value 90 in the second quality index storage unit 115. As a result, as shown in Figure 7, the second quality index storage unit 115 stores the corrected OSNR database in which the new OSNR index value 90 is recorded. The NMS 80 accesses the second quality index storage unit 115 periodically or irregularly to obtain the corrected OSNR database. Once the NMS 80 obtains the corrected OSNR database, it manages the corrected OSNR database.

[0050] The second quality estimation unit 127 estimates the OSNR of the signal light L1. The OSNR of the signal light L1 is an example of the second quality. For example, the second quality estimation unit 127 estimates the OSNR of the signal light L1 between ROADM40S and 40G based on the measured OSNR of the dummy light Ld managed as measurement data by the NMS80 and the new OSNR index value 90. The second quality estimation unit 127 can obtain the measured OSNR of the dummy light Ld from the NMS80 via the input unit 130 and output unit 140. The second quality estimation unit 127 can also obtain the new OSNR index value 90 from the second quality index storage unit 115. Once the second quality estimation unit 127 estimates the OSNR of the signal light L1, it stores the estimated OSNR of the signal light L1 in the second quality storage unit 116. Details of the process for estimating the OSNR of the signal light L1 will be described later.

[0051] The second quality notification unit 128 notifies a carrier's terminal (hereinafter referred to as "carrier terminal") that requests the OSNR of signal light L1 during actual operation of the optical network NW of an estimated value of the OSNR of signal light L1. Depending on the carrier operating the optical network NW (for example, a telecommunications carrier), it may be necessary to check for the location of a failure in ROADM40S, ..., 40G or to check for signs of failure. In this case, the carrier terminal requests the second quality notification unit 128 to notify it of the OSNR of signal light L1.

[0052] When the second quality notification unit 128 receives a request for notification of the OSNR of the signal light L1, it accesses the second quality storage unit 116 to obtain an estimated value of the OSNR of the signal light L1 and notifies the operator terminal of the estimated value of the OSNR of the signal light L1 via the output unit 140. As a result, the estimated value of the OSNR of the signal light L1 is output, for example, on the screen of the operator terminal.

[0053] Referring to Figures 8 to 16, three cases in which ROADM40G estimates the OSNR of signal light L1 will be described individually. ROADM40G can access NMS80 and obtain post-wavelength data, pre-wavelength data, measurement data, and corrected OSNR database managed by NMS80.

[0054] First, let's explain Case #1 with reference to Figures 8 to 10. Case #1 is the case in which a dummy light Ld with wavelength λp, including wavelengths λp1,..., λp5, is translated from ROADM40S to ROADM40G in relation to a signal light L1 with wavelength λ1.

[0055] In Case #1, the second quality estimation unit 127 obtains the measured OSNR of the dummy light Ld at wavelength λp, measured by ROADM40G, and the corrected OSNR database from NMS80. The second quality estimation unit 127 may also obtain the measured OSNR of the dummy light Ld at wavelength λp from the measured value storage unit 113. Alternatively, the second quality estimation unit 127 may obtain the corrected OSNR database from the second quality index storage unit 115.

[0056] The second quality estimation unit 127 obtains the measured OSNR of the dummy light Ld at wavelength λp and the corrected OSNR database, and as shown in Figure 9, matches the measured OSNR values ​​for each wavelength λp1,...,λp5 included in wavelength λp with the new OSNR index value 90 included in the corrected OSNR database. Since the new OSNR index value 90 is generated based on the dummy light Ld at wavelength λp and the span loss, the measured OSNR values ​​for each are likely to match the new OSNR index value 90. For this reason, the second quality estimation unit 127 estimates the corresponding value 90X on the new OSNR index value 90 corresponding to wavelength λ1 as the OSNR of the signal light L1.

[0057] As shown in Figure 10, the measured values ​​of the OSNR for each wavelength λp1,..., λp5 may not match the new OSNR index value 90. In this case, the second quality estimation unit 127 may individually calculate the discrepancy between each OSNR and the new OSNR index value 90, and estimate the OSNR of the signal light L1 based on the new OSNR index value 90 and the discrepancy. For example, the second quality estimation unit 127 may modify the new OSNR index value 90 to match each OSNR based on the individually calculated discrepancy. After modifying the new OSNR index value 90, the second quality estimation unit 127 estimates the corresponding value 90Y of the modified new OSNR index value (not shown) corresponding to wavelength λ1 as the OSNR of the signal light L1.

[0058] Next, Case #2 will be explained with reference to Figures 11 to 13. Case #2 is a case in which, as shown in Figure 11, a signal light L1 with wavelength λ1 is translated from ROADM40S to ROADM40G with interruptions in between, by a dummy light Ld with wavelength λq including wavelengths λq1,..., λq5 and a dummy light Ld with wavelength λr including wavelengths λr1,..., λr5.

[0059] Specifically, the ROADM40S receives a signal light L2 with wavelength λr from upstream. As a result, the ROADM40S transmits WDM light Lw2, which is a combination of signal light L1 with wavelength λ1, signal light L2 with wavelength λr, and dummy light Ld with wavelength λq. In the ROADM40X, the signal light L2 included in WDM light Lw2 is branched, and signal light L3 with wavelength λq is inserted. As a result, the ROADM40X transmits WDM light Lw3, which is a combination of signal light L1 with wavelength λ1, signal light L3 with wavelength λq, and dummy light Ld with wavelength λr. In the ROADM40G, the signal light L1 included in WDM light Lw3 is branched, and signal light L3 is excluded from the branching. The ROADM40G outputs signal light L3 downstream.

[0060] In Case #2, the second quality estimation unit 127 obtains the OSNR measurement value of dummy light Ld with wavelength λr measured by ROADM40G from NMS80 as the first measurement value. The second quality estimation unit 127 also obtains the OSNR measurement value of dummy light Ld with wavelength λq measured by ROADM40G from NMS80 as the second measurement value. Furthermore, the second quality estimation unit 127 obtains the corrected OSNR database from NMS80.

[0061] When the second quality estimation unit 127 obtains the first measurement, the second measurement, and the corrected OSNR database, it matches the measured values ​​of each OSNR of wavelengths λq1, ..., λq5 included in wavelength λq with the new OSNR index value 91 included in the corrected OSNR database, as shown in Figure 12. Since the new OSNR index value 91 is generated based on the dummy light Ld and span loss of wavelength λq, the measured values ​​of each OSNR are likely to match the new OSNR index value 91. For this reason, the second quality estimation unit 127 estimates the corresponding value 91X on the new OSNR index value 91 corresponding to wavelength λ1 as part of the OSNR of signal light L1.

[0062] Furthermore, when the second quality estimation unit 127 obtains the first measurement value, the second measurement value, and the corrected OSNR database, it matches the measured values ​​of each OSNR of wavelengths λr1,..., λr5 included in wavelength λr with the new OSNR index value 92, as shown in Figure 13. Since the new OSNR index value 92 is generated based on the dummy light Ld and span loss of wavelength λr, the measured values ​​of each OSNR are likely to match the new OSNR index value 92. For this reason, the second quality estimation unit 127 estimates the corresponding value 92X on the new OSNR index value 92 corresponding to wavelength λ1 as the remainder of the OSNR of signal light L1.

[0063] The second quality estimation unit 127 estimates a portion and the remainder of the OSNR of the signal light L1, and then sums them up based on the following formula (1) to estimate the overall OSNR of the signal light L1 at wavelength λ1. <Formula (1)> 1 / OSNR(whole)={1 / OSNR(part)}+{1 / OSNR(remainder)}

[0064] As a result, even in case #2, ROADM40G can estimate the overall OSNR of the signal light L1 with wavelength λ1. If the measured values ​​of each OSNR do not match the new OSNR index value 91 or the new OSNR index value 92, the second quality estimation unit 127 can apply the deviation amount explained in case #1.

[0065] Next, we will explain Case #3 with reference to Figures 14 to 16. Case #3 is a case in which, as shown in Figure 14, a dummy light Ld with wavelength λs including wavelengths λs1,..., λs5 and a dummy light Ld with wavelength λt including wavelengths λt1,..., λt5 do not translate from ROADM40S to ROADM40G with interruptions in between, relative to a signal light L1 with wavelength λ1.

[0066] To explain in more detail, the ROADM40S receives a signal light L4 with wavelength λt from upstream. As a result, the ROADM40S transmits WDM light Lw4, which is a combination of signal light L1 with wavelength λ1, signal light L4 with wavelength λt, and dummy light Ld with wavelength λs. In the ROADM40X, the signal light L4 included in WDM light Lw4 is branched, and signal light L5 with wavelength λs is inserted. As a result, the ROADM40X transmits WDM light Lw5, which is a combination of signal light L1 with wavelength λ1, signal light L5 with wavelength λs, and dummy light Ld with wavelength λt.

[0067] In ROADM40J, a signal light L6 with wavelength λt is inserted. As a result, ROADM40J transmits WDM light Lw6, which is a combination of signal light L1 with wavelength λ1, signal light L5 with wavelength λs, and signal light L6 with wavelength λt. In ROADM40G, signal light L1 included in WDM light Lw6 is branched, and signal lights L5 and L6 are excluded from the branching. ROADM40G outputs signal lights L5 and L6 downstream of ROADM40G.

[0068] In Case #3, the second quality estimation unit 127 acquires the measured OSNR of dummy light Ld at wavelength λs, measured by ROADM40X, as the third measured value from NMS80. The second quality estimation unit 127 also acquires the measured OSNR of dummy light Ld at wavelength λt, measured by ROADM40J, as the fourth measured value from NMS80. Furthermore, the second quality estimation unit 127 acquires the measured input optical power as the fifth measured value from NMS80. In addition, the second quality estimation unit 127 acquires a corrected OSNR database from NMS80.

[0069] When the second quality estimation unit 127 obtains the third measurement, the fourth measurement, the fifth measurement, and the corrected OSNR database, it matches the measured values ​​of each OSNR of wavelengths λs1, ..., λs5 included in wavelength λs with the new OSNR index value 93 included in the corrected OSNR database, as shown in Figure 15. Since the new OSNR index value 93 is generated based on the dummy light Ld and span loss of wavelength λs, the measured values ​​of each OSNR are likely to match the new OSNR index value 93. For this reason, the second quality estimation unit 127 estimates the corresponding value 93X on the new OSNR index value 93 corresponding to wavelength λ1 as the first estimated value of the OSNR of signal light L1.

[0070] Furthermore, when the second quality estimation unit 127 obtains the third measurement, the fourth measurement, the fifth measurement, and the corrected OSNR database, it matches the measured values ​​of each OSNR of wavelengths λt1,...,λt5 included in wavelength λt with the new OSNR index value 94, as shown in Figure 16. Since the new OSNR index value 94 is generated based on the dummy light Ld and span loss of wavelength λt, the measured values ​​of each OSNR are likely to match the new OSNR index value 94. For this reason, the second quality estimation unit 127 estimates the corresponding value 94X on the new OSNR index value 94 corresponding to wavelength λ1 as the second estimated value of the OSNR of signal light L1.

[0071] Furthermore, the second quality estimation unit 127 calculates a third estimated value of the OSNR of the signal light L1, which cannot be estimated based on the dummy light Ld of wavelengths λs and λt, based on the following formula (2). Note that NF (Noise Figure) is an example of the specification value of the optical amplifier, and specifically corresponds to the noise figure of the optical amplifier 45. <Formula (2)> OSNR (3rd Estimate) = 5th Measured Value - NF - Constant

[0072] The constants mentioned above are uniquely determined for each signal band by multiplying Planck's constant h, optical frequency v, and receiving bandwidth Δf (h × v × Δf). For example, for the C band with a center frequency equivalent of "193.625 (THz)" (center wavelength equivalent of 1548.3 (nm)), a unique constant of "-57.9 (dB)" is determined. For the L band with a center frequency equivalent of "188.5 (THz)" (center wavelength equivalent of 1590.4 (nm)), a unique constant of "-58.1 (dB)" is determined.

[0073] The second quality estimation unit 127 estimates the first and second estimated values ​​of the OSNR of the signal light L1, calculates the third estimated value, and then sums them up based on the following formula (3) to estimate the overall OSNR of the signal light L1 at wavelength λ1. <Formula (3)> 1 / OSNR(total) = {1 / OSNR(first estimate)} +{1 / OSNR(second estimate)} +{1 / OSNR(3rd estimate)}

[0074] As a result, even in case #3, ROADM40G can estimate the overall OSNR of the signal light L1 with wavelength λ1. If the measured values ​​of each OSNR do not match the new OSNR index value 93 or the new OSNR index value 94, the second quality estimation unit 127 can apply the deviation amount explained in case #1.

[0075] Refer to Figure 17 to explain an example of ROADM40G operation. Note that ROADM40S, 40X, 40Y, and 40J operate essentially the same as ROADM40G, so detailed explanations are omitted.

[0076] First, the second quality notification unit 128 determines whether or not notification of the OSNR of signal light L1 has been requested (step S1). For example, during actual operation of the optical network NW, the second quality notification unit 128 determines whether or not notification of the OSNR of signal light L1 has been requested via the NMS 80 from the operator terminal of the operator operating the optical network NW.

[0077] If notification of the OSNR of signal light L1 is not requested (step S1: NO), the second quality notification unit 128 terminates processing. If notification of the OSNR of signal light L1 is requested (step S1: YES), the second quality estimation unit 127 determines whether or not there is a drop in the signal light L1 (step S2). For example, the second quality estimation unit 127 determines whether or not there is a drop in the signal light L1 by acquiring and checking the pre-wavelength data and post-wavelength data managed by the NMS 80.

[0078] If there is no branching in the signal light L1 (step S2: NO), the second quality estimation unit 127 terminates processing. If there is branching in the signal light L1 (step S2: YES), the second quality estimation unit 127 checks the wavelength of the target signal light (step S3). In this embodiment, the second quality estimation unit 127 checks the wavelength λ1 of the signal light L1 as the target signal light.

[0079] Upon confirming the wavelength of the target signal light, the second quality estimation unit 127 determines whether or not it falls under case #1 (step S4). The second quality estimation unit 127 can determine whether or not it falls under case #1 by acquiring and confirming the pre-wavelength data and post-wavelength data managed by the NMS 80. If it falls under case #1 (step S4: YES), the second quality estimation unit 127 acquires the OSNR measured by ROADM#G (step S5). That is, the second quality estimation unit 127 acquires the measured OSNR values ​​for each wavelength λp1,...,λp5 measured by ROADM40G.

[0080] If the case does not fall under Case #1 (Step S4: NO), the second quality estimation unit 127 determines whether or not it falls under Case #2 (Step S6). The second quality estimation unit 127 can determine whether or not it falls under Case #2 by checking the pre-wavelength data and post-wavelength data. If it falls under Case #2 (Step S6: YES), the OSNRs measured by ROADM #1 and ROADM #G are obtained (Step S7). That is, the second quality estimation unit 127 obtains the measured OSNRs for each wavelength λq1,...,λq5 measured by ROADM40X and the measured OSNRs for each wavelength λr1,...,λr5 measured by ROADM40G.

[0081] If the case does not fall under Case #2 (Step S6: NO), the second quality estimation unit 127 obtains the OSNRs measured by ROADM #1 and ROADM #J (Step S8). In other words, if the case does not fall under Case #2, the second quality estimation unit 127 determines that the case falls under Case #3. In this case, the second quality estimation unit 127 obtains the measured OSNR values ​​for each wavelength λs1,..., λs5 measured by ROADM40X and the measured OSNR values ​​for each wavelength λt1,..., λt5 measured by ROADM40J.

[0082] After obtaining the OSNR measured by ROADM#1 and ROADM#J, the second quality estimation unit 127 then calculates the underperformance OSNR (step S9). That is, the second quality estimation unit 127 calculates a third estimated value of the OSNR of the signal light L1 as the underperformance OSNR.

[0083] Depending on case #1, case #2, or case #3, once any of the processes in steps S5, S7, or S9 is completed, the second quality estimation unit 127 acquires the span loss (step S10). More specifically, the second quality estimation unit 127 acquires the measured span loss value that the NMS 80 manages as measurement data. The second quality estimation unit 127 may also acquire the measured span loss value from the measured value storage unit 113.

[0084] Once the span loss is obtained, the second quality estimation unit 127 corrects the OSNR database (step S11). Specifically, the second quality estimation unit 127 corrects at least one of the first OSNR index value 85, the second OSNR index value 86, and the third OSNR index value 87 recorded in the OSNR database based on the obtained span loss measurement value.

[0085] After correcting the OSNR database, the second quality estimation unit 127 performs matching (step S12) and determines whether there is a match or a mismatch (step S13). That is, the second quality estimation unit 127 matches the measured values ​​of each OSNR of the dummy optical Ld with the new OSNR index values ​​included in the corrected OSNR database and determines whether there is a match or not.

[0086] If the measured OSNR values ​​for each dummy light Ld match the new OSNR index values ​​included in the corrected OSNR database (step S13: YES), the second quality estimation unit 127 estimates the OSNR of the target signal light (step S15). That is, the second quality estimation unit 127 estimates the OSNR of the signal light L1 as the target signal light based on the estimation methods for cases #1, #2, and #3 described above.

[0087] If the measured OSNR values ​​for each dummy light Ld do not match the new OSNR index values ​​included in the corrected OSNR database (step S13: NO), the second quality estimation unit 127 calculates the discrepancy between the measured OSNR values ​​for each dummy light Ld and the new OSNR index values ​​included in the corrected OSNR database (step S14), and estimates the OSNR of signal light L1 based on the discrepancy. Once the second quality estimation unit 127 has estimated the OSNR of signal light L1, it notifies the estimated OSNR value of signal light L1 to the carrier terminal that requested notification of the OSNR of signal light L1, and then terminates the process.

[0088] Refer to Figure 18 to explain the effects of this case in comparison with three comparative examples.

[0089] In Comparative Example 1, the OSNR of signal light L1 is measured using a spectrum analyzer and an optical coupler. In this case, it is not possible to measure the OSNR of signal light L1 during actual operation of the optical network NW. Furthermore, for example, the installation of measuring equipment such as a spectrum analyzer in the ROADM40G may increase the manufacturing cost of the ROADM40G.

[0090] In Comparative Example 2, the OSNR of signal light L1 is measured using transponders 10 and 20. In this case, it is not possible to measure the OSNR of signal light L1 with ROADM 40S, 40X, 40Y, 40J, and 40G. Furthermore, the measurement accuracy of the OSNR of signal light L1 is approximately ±5 dB, which is not as high as that of the example described later.

[0091] In Comparative Example 3 (for example, Japanese Patent Publication No. 2015-39180), the OSNR of the signal light L1 is measured using a Mach-Zehnder delay interferometer or an oscilloscope. In this case, the ROADM40G is required to be equipped with measuring instruments such as a Mach-Zehnder delay interferometer, which may increase the manufacturing cost of the ROADM40G.

[0092] In contrast, in the embodiment, the OSNR of the signal light L1 is measured during actual operation of the optical network NW. Furthermore, for example, the ROADM40G does not require the installation of measuring instruments such as a spectrum analyzer or a Mach-Zehnder delay interferometer. Moreover, the OSNR of the signal light L1 can be measured with each of the ROADM40S, 40X, 40Y, 40J, and 40G, and the measurement accuracy is approximately ±1 dB, which is an improvement over Comparative Example 2.

[0093] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to specific embodiments, and various modifications and changes are possible within the scope of the gist of the invention as described in the claims.

[0094] For example, the NMS 80 may be provided with at least one of the following: a span loss measurement unit 123, an input optical power measurement unit 124, a first quality measurement unit 125, and a second quality estimation unit 127. Furthermore, various measurement values ​​may be transmitted and received via OSC optical Lo1 and LO2 without going through the NMS 80. Additionally, in case #2, for example, the dummy optical light Ld of wavelength λq and the signal optical light L3 of wavelength λq may not be transmitted, while the signal optical lights L1 and L2 of wavelengths λ1 and λr, respectively, and the dummy optical light Ld of wavelength λr may be transmitted.

[0095] Furthermore, the following additional information is disclosed regarding the above explanation. (Note 1) An optical transmission system comprising: a first optical transmission device that transmits a first signal light in actual operation and a first pseudo-light having a different wavelength from the first signal light; a second optical transmission device that receives the first signal light and the first pseudo-light from the first optical transmission device; a measurement unit that measures the first quality of the first pseudo-light between the first optical transmission device and the second optical transmission device; and an estimation unit that estimates the second quality of the first signal light between the first optical transmission device and the second optical transmission device based on the first quality and an index value of wavelength dependence in the signal band. (Note 2) The optical transmission system according to Note 1, characterized in that the second optical transmission device has an OCM, the first optical transmission device switches between emitting the first pseudo-light and stopping the emission of the first pseudo-light, and the measuring unit measures the first quality based on a first measurement value by the OCM during the emission and a second measurement value by the OCM during the stopping of the emission. (Note 3) The optical transmission system according to Note 1 or 2, characterized in that the first quality and the second quality are OSNR. (Note 4) The optical transmission system according to Note 1, characterized in that the index value shows a correspondence between a plurality of wavelengths, including the first wavelength of the first signal light and the second wavelength of the first pseudo-light, and at least the first quality. (Note 5) The optical transmission system according to Note 1, characterized in that the index value is measured before the commencement of operation of the optical communication service performed between the first optical transmission device and the second transmission device based on the first signal light. (Appendix 6) The optical transmission system according to Appendix 1, further comprising a third optical transmission device that receives the first pseudo-light from the first optical transmission device, switches the received first pseudo-light to a second pseudo-light having a different wavelength from the first pseudo-light, and transmits it to the second optical transmission device, wherein the measuring unit measures the third quality of the first pseudo-light between the first optical transmission device and the third optical transmission device, and the fourth quality of the second pseudo-light between the third optical transmission device and the second optical transmission device, and the estimation unit estimates the second quality based on the third quality, the fourth quality, and the index value. (Appendix 7) The optical transmission system according to Appendix 1, further comprising a third optical transmission device that receives the first pseudo-light from the first optical transmission device, switches the received first pseudo-light to a second signal light of any wavelength belonging to the wavelength of the first pseudo-light, and transmits it to the second optical transmission device, wherein the measuring unit measures the third quality of the first pseudo-light between the first optical transmission device and the third optical transmission device, and the estimation unit estimates the second quality based on the third quality and the index value. (Appendix 8) The optical transmission system according to Appendix 7, characterized in that the measuring unit further measures the span loss of the first pseudo-light between the first optical transmission device and the second optical transmission device, and the estimation unit estimates the second quality based on at least one of the first quality, the span loss, the index value, and the input optical power of the second signal light to the second optical transmission device at any wavelength belonging to the wavelength of the first pseudo-light. (Note 9) The optical transmission system according to Note 7, characterized in that the measurement unit calculates a fifth quality of the second signal light between the third optical transmission device and the second optical transmission device based on the input optical power of the second signal light to the second optical transmission device and the specification value of the optical amplifier provided in the second optical transmission device, and the estimation unit estimates the second quality based on the third quality, the fifth quality, and the index value. (Note 10) The optical transmission system according to Note 1, characterized in that the measuring unit or estimation unit is provided in at least one of the first optical transmission device, the second optical transmission device, the third optical transmission device located between the first optical transmission device and the second optical transmission device, and a control device that controls the operation of the first optical transmission device, the second optical transmission device and the third optical transmission device. (Note 11) The optical transmission system according to Note 1, characterized in that the measurement unit further measures the span loss of the first pseudo-light between the first optical transmission device and the second optical transmission device, corrects the index value based on the span loss, calculates the amount of deviation between the first quality and the corrected index value, and the estimation unit estimates the second quality based on the amount of deviation. (Note 12) An optical transmission system comprising: a first optical transmission device that transmits a first signal light and a second signal light of different wavelengths, both of which are in actual operation; a second optical transmission device that receives the first signal light and the second signal light and transmits the first signal light and a plurality of pseudo-lights of wavelengths including the wavelength of the second signal light; a third optical transmission device that receives the first signal light and the first pseudo-light from the second optical transmission device; a measurement unit that measures the first quality of the first pseudo-light between the second optical transmission device and the third optical transmission device; and an estimation unit that estimates the second quality of the first signal light between the first optical transmission device and the third optical transmission device based on the first quality and an index value of wavelength dependence in the signal band. (Note 13) A quality estimation method for estimating the signal quality of a first signal light between a first optical transmission device that transmits a first signal light in actual operation and a first pseudo-light having a different wavelength from the first signal light, and a second optical transmission device that receives the first signal light and the first pseudo-light from the first optical transmission device, characterized in that a second quality representing the signal quality of the first signal light between the first optical transmission device and the second optical transmission device is estimated based on a first quality representing the signal quality based on a measurement of the first pseudo-light between the first optical transmission device and the second optical transmission device, and an index value of wavelength dependence in the signal band. [Explanation of symbols]

[0096] NW Optical Network 10,20 transponders 40S, 40X, 40Y, 40J, 40G ROADM 100 Control Unit 125 1st Quality Measurement Department 127 Second quality estimation section L1,L2,L3,L4,L5,L6 signal light Ld Dummy Light Lw1,Lw2,Lw3,Lw4,Lw5,Lw6 WDM light

Claims

1. A first optical transmission device that transmits a first signal light in actual operation and a first pseudo-light having a different wavelength from the first signal light, A second optical transmission device that receives the first signal light and the first pseudo-light from the first optical transmission device, A measuring unit for measuring the first quality of the first pseudo-light between the first optical transmission device and the second optical transmission device, An estimation unit that estimates the second quality of the first signal light between the first optical transmission device and the second optical transmission device based on the first quality and an index value of wavelength dependence in the signal band, An optical transmission system.

2. The second optical transmission device has an OCM (Optical channel monitor), The first optical transmission device switches between emitting the first pseudo-light and stopping the emission of the first pseudo-light. The measuring unit measures the first quality based on the first measurement value obtained by the OCM during light emission and the second measurement value obtained by the OCM during light emission cessation. The optical transmission system according to feature 1.

3. The first quality and the second quality are the OSNR (Optical Signal-to-Noise Ratio). The optical transmission system according to claim 1 or 2, characterized in that it is as described above.

4. The index value indicates the correspondence between a plurality of wavelengths, including the first wavelength of the first signal light and the second wavelength of the first pseudo-light, and at least the first quality. The optical transmission system according to feature 1.

5. The third optical transmission device further includes a third optical transmission device that receives the first pseudo-light from the first optical transmission device, switches the received first pseudo-light to a second pseudo-light having a different wavelength from the first pseudo-light, and transmits it to the second optical transmission device. The measuring unit measures the third quality of the first pseudo-light between the first optical transmission device and the third optical transmission device, and the fourth quality of the second pseudo-light between the third optical transmission device and the second optical transmission device. The estimation unit estimates the second quality based on the third quality, the fourth quality, and the index value. The optical transmission system according to feature 1.

6. The third optical transmission device further includes a third optical transmission device that receives the first pseudo-light from the first optical transmission device, switches the received first pseudo-light to a second signal light of any wavelength belonging to the wavelength of the first pseudo-light, and transmits it to the second optical transmission device. The measurement unit measures the third quality of the first pseudo-light between the first optical transmission device and the third optical transmission device. The estimation unit estimates the second quality based on the third quality and the index value. The optical transmission system according to feature 1.

7. The measurement unit further measures the span loss of the first pseudo-light between the first optical transmission device and the second optical transmission device. The estimation unit estimates the second quality based on the first quality, the span loss, the index value, and at least one of the input optical power of the second signal light to the second optical transmission device at any wavelength belonging to the wavelength of the first pseudo-light. The optical transmission system according to claim 6.

8. The measurement unit or estimation unit is provided in at least one of the first optical transmission device, the second optical transmission device, the third optical transmission device located between the first optical transmission device and the second optical transmission device, and a control device that controls the operation of the first optical transmission device, the second optical transmission device and the third optical transmission device. The optical transmission system according to feature 1.

9. The measurement unit further measures the span loss of the first pseudo-light between the first optical transmission device and the second optical transmission device, corrects the index value based on the span loss, and calculates the deviation between the first quality and the corrected index value. The estimation unit estimates the second quality based on the deviation amount. The optical transmission system according to feature 1.

10. The first optical transmission device transmits a first signal light and a second signal light of different wavelengths, both of which are currently in actual operation. A second optical transmission device that receives the first signal light and the second signal light, and transmits the first signal light and a first pseudo-light of a plurality of wavelengths including the wavelength of the second signal light, A third optical transmission device that receives the first signal light and the first pseudo-light from the second optical transmission device, A measuring unit for measuring the first quality of the first pseudo-light between the second optical transmission device and the third optical transmission device, An estimation unit that estimates the second quality of the first signal light between the first optical transmission device and the third optical transmission device based on the first quality and an index value of wavelength dependence in the signal band, An optical transmission system.

11. A quality estimation method for estimating the signal quality of a first signal light between a first optical transmission device that transmits a first signal light in actual operation and a first pseudo-light having a different wavelength from the first signal light, and a second optical transmission device that receives the first signal light and the first pseudo-light from the first optical transmission device, wherein Based on a first quality representing the signal quality based on the measurement of the first pseudo-light between the first optical transmission device and the second optical transmission device, and an index value of the wavelength dependence in the signal band, a second quality representing the signal quality of the first signal light between the first optical transmission device and the second optical transmission device is estimated. A quality estimation method characterized by the following:

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