Optical transmission path characteristics estimation apparatus, optical transmission system, and optical transmission path characteristics estimation method

Abstract

To provide an optical transmission path characteristic estimation device, an optical transmission system, and an optical transmission path characteristic estimation method, which estimate a characteristic value caused by the polarization characteristic of an optical transmission path.SOLUTION: An optical transmission path characteristic estimation device estimates the polarization characteristic values of an optical path that includes a first section in service of an optical communication service using multiple wavelengths and a second section not in service, and includes an acquisition unit that acquires a first polarization characteristic value for each of the multiple wavelengths in the first section and acquires a second polarization characteristic value for each of the multiple wavelengths in the second section on the basis of information representing the operational state of the optical communication service, and a calculation unit that calculates a wavelength-specific polarization characteristic value for each of the multiple wavelengths of the optical path on the basis of the first polarization characteristic value and the second polarization characteristic value.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] This relates to an optical transmission path characteristic estimation device, an optical transmission system, and an optical transmission path characteristic estimation method.

Background Art

[0002] It is known that multi - value modulation methods such as QPSK (Quadrature Phase Shift Keying) and 16QAM (Quadrature Amplitude Modulation) are selected using the maximum value of the PMD (Polarization Mode Dispersion) value estimated based on design values such as the standard value of an optical fiber. Also, a technique for calculating the maximum value of the PMD value that varies over time by multiplying the average value of the PMD value for each wavelength by a predetermined ratio is known. The ratio of the maximum value to the average value of the PMD value is described, for example, in Table 9 - 2 of ITU - T Recommendation G.680 (see, for example, Patent Document 1).

[0003] In addition, it is known that the design of an optical fiber transmission path varies widely for each project, and it is almost impossible to prepare a simulated transmission path equivalent to the actual transmission path (see, for example, Patent Document 2). Also, a design method for an optical fiber transmission path for eliminating signal degradation due to PDL (Polarization Dependent Loss) is known (see, for example, Patent Document 3).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when an optical communication service is provided and operated for customers, it may be difficult to accurately estimate the limit values (such as maximum values and worst values) of polarization characteristic values such as the above-described PMD value and PDL value. Specifically, in the case of an optical network in which a plurality of relay nodes are arranged between a transmission node and a reception node, it is rare that the entire transmission section from the transmission node to the reception node is used for the optical communication service. Depending on the customer, for example, a part of the transmission section from the transmission node to the relay node is used for the optical communication service.

[0006] In addition, in the optical communication service, different wavelengths are assigned to each customer. For this reason, a part of the transmission section may be used for a customer to whom a specific wavelength is assigned, and another transmission section may be used for another customer to whom a different wavelength from this wavelength is assigned. Thus, in an optical communication service using a plurality of wavelengths, an in-operation section during which the optical communication service is in operation and an out-of-operation section during which the optical communication service is not in operation are mixed.

[0007] When the in-operation section and the out-of-operation section are mixed, it is difficult to perform wavelength sweeping end-to-end from the transmission node to the reception node for the entire wavelengths that can be assigned to the customers. Therefore, the polarization characteristic value cannot be obtained by wavelength sweeping, and it is difficult to estimate the limit value of the polarization characteristic value. In addition, although a measuring device for measuring the PMD value is provided in the relay node and the reception node, it is difficult to measure the PMD value with the measuring device because the wavelength characteristics cannot be measured in the out-of-operation section.

[0008] In addition, polarization characteristic values that change randomly over time, such as the PMD value and the PDL value, may have a large measurement error even when measured with a measuring device, and there is also a possibility that the estimation accuracy is low even when estimating the transmission penalty (degradation amount) that varies over time based on the measured value.

[0009] Therefore, in one aspect, an object is to provide an optical transmission line characteristic estimation apparatus, an optical transmission system, and an optical transmission line characteristic estimation method for estimating characteristic values resulting from the polarization characteristics of an optical transmission line.

Means for Solving the Problems

[0010] In one embodiment, an optical transmission line characteristic estimation apparatus is an optical transmission line characteristic estimation apparatus that estimates polarization characteristic values of an optical path in which a first section during service operation and a second section outside service operation of an optical communication service using a plurality of wavelengths are mixed. The apparatus includes an acquisition unit that acquires first polarization characteristic values of each of the plurality of wavelengths in the first section and second polarization characteristic values of each of the plurality of wavelengths in the second section based on information indicating an operation state of the optical communication service, and a calculation unit that calculates wavelength-specific polarization characteristic values of each of the plurality of wavelengths of the optical path based on the first polarization characteristic values and the second polarization characteristic values.

[0011] Also, in one embodiment, an optical transmission system includes a plurality of nodes having an optical device with a CDC function and a wavelength-variable optical transceiver. Based on an instruction from the above-described optical transmission line characteristic estimation apparatus, the optical transmission system sets the wavelength of the optical transceiver and the path of the optical device with the CDC function, and acquires the second polarization characteristic value.

[0012] Furthermore, in one embodiment, an optical transmission line characteristic estimation apparatus is an optical transmission line characteristic estimation apparatus that estimates a characteristic value that varies temporally according to the polarization characteristic of an optical transmission line including a plurality of nodes arranged from one end to the other end of an optical network. The apparatus includes an acquisition unit that acquires a signal quality index of signal light after propagating through the optical transmission line from a receiving node arranged at the other end of the optical network, a calculation unit that calculates a quality change amount over a certain period of the signal quality index, and an estimation unit that estimates the characteristic value based on the quality change amount.

Advantages of the Invention

[0013] Characteristic values resulting from the polarization characteristics of an optical transmission line can be estimated.

Brief Description of the Drawings

[0014]

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Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments for carrying out the present case will be described with reference to the drawings.

[0016] (First Embodiment) As shown in FIG. 1, the optical network NW includes a plurality of nodes #1, ···, #5. The nodes #1, ···, #5 include, for example, ROADM (Reconfigurable Optical Add / Drop Multiplexer) devices. For example, the node #1 is arranged at one end of the optical network NW, and the node #5 is arranged at the other end of the optical network NW. The nodes #2, ···, #4 are arranged as relay nodes between the node #1 and the node #5.

[0017] The node #2 is connected to the adjacent nodes #1 and #3 by the optical fiber 20. Since the connection forms of the nodes #3 and #4 are basically the same as that of the node #2, detailed description thereof will be omitted. The node #2 includes an optical receiver R2 that receives signal light (specifically, wavelength-division multiplexed signal light) and an optical transmitter T2 that transmits signal light.

[0018] The optical receiver R2 includes a measuring device M2 that measures the DGD (Differential Group Delay) in PMD as the PMD value. The PMD value is an example of a polarization characteristic value. Instead of the PMD value, a PDL value may be adopted as the polarization characteristic value. Note that DGD is sometimes called the first-order PMD amount. The configurations of nodes #1, #3, ···, #5 are basically the same as that of node #2. Therefore, for example, node #1 is provided with an optical transmitter T1. Further, node #5 includes an optical receiver R5 that includes a measuring device M5. Note that node #3 that includes another measuring device Mx that measures the polarization fluctuation speed may be included in the optical network NW in combination with the measuring device M3.

[0019] Based on the estimation instruction transmitted from the operation terminal 10, the optical network controller 100 controls the operations of the plurality of nodes #1, ···, #5. Although details will be described later, when the optical network controller 100 detects the estimation instruction, it acquires the PMD value from at least one of nodes #1, ···, #5. When the optical network controller 100 acquires the PMD value, based on the acquired PMD value, it estimates the worst value (or maximum value), which is the limit value of the PMD value of the optical transmission line corresponding to the entire transmission section from one end to the other end of the optical network NW.

[0020] Thereby, even if an excessive PMD value is estimated based on the design value of the optical transmission line as the worst value, it is possible to specify that the worst value is excessive based on the actual measurement of the PMD value. Therefore, when it is determined that the worst value is excessive, the optical network controller 100 can select and use an appropriate signal type (for example, modulation method, transmission capacity, baud rate, etc.) based on the estimated worst value.

[0021] Referring to FIG. 2, the details of node #2 will be described. Since nodes #1, #3, ···, #5 have the same configuration as node #2, detailed descriptions thereof will be omitted. Node #2 includes an optical transceiver 30 and a plurality of wavelength selection units 35, ···, 38. The optical transceiver 30 includes the above-described optical receiver R2, optical transmitter T2, and MCSs (Multicast Switches) 31, 32 of N×M (both N and M are natural numbers). Instead of MCSs 31, 32, an N×M WSS (Wavelength Selective Switch) or other devices may be employed, but it is necessary to be an optical device having a CDC (Colorless Directionless Contentionless) function. This is to realize measuring the polarization characteristic value at a desired path and at a desired wavelength using one available optical transceiver through which signals are not passing.

[0022] The optical receiver R2 includes a plurality of digital coherent receivers Rx. Although not shown, each digital coherent receiver Rx includes a wavelength-variable light source whose wavelength can be set by the optical network controller 100 together with the above-described measuring device M2 (hereinafter, also appropriately referred to as a channel). Each digital coherent receiver Rx is connected to MCS 31. The optical transmitter T2 includes a plurality of digital coherent transmitters Tx. Although not shown, each digital coherent transmitter Tx includes a wavelength-variable light source whose wavelength can be set by the optical network controller 100. Each digital coherent transmitter Tx is connected to MCS 32.

[0023] The wavelength selection unit 35 includes WSSs 35M, 35D. The wavelength selection unit 36 includes WSSs 36M, 36D. The wavelength selection unit 37 includes WSSs 37M, 37D. The wavelength selection unit 38 includes WSSs 38M, 38D.

[0024] WSS35M, 36M, 37M, and 38M are all connected to MCS32. WSS35M, 36M, 37M, and 38M multiplex the input wavelength lights of different wavelengths according to the settings and output them as signal light. For example, WSS36M multiplexes the wavelength light input from MCS32 and the wavelength lights input from WSS35D, 37D, and 38D, and outputs them as signal light to the adjacent node #3.

[0025] WSS35D, 36D, 37D, and 38D are all connected to MCS31. WSS35D, 36D, 37D, and 38D demultiplex the input signal light into wavelength lights of different wavelengths according to the settings and output them. For example, WSS35D demultiplexes the signal light transmitted from and input by the adjacent node #1 into wavelength lights of different wavelengths, outputs a part of the wavelength light to MCS31, and outputs the remaining part of the wavelength light to any one of WSS36M, 37M, and 38M.

[0026] Referring to FIG. 3, the hardware configuration of the optical network controller 100 will be described.

[0027] The optical network controller 100 includes a CPU (Central Processing Unit) 100A as a processor, a RAM (Random Access Memory) 100B and a ROM (Read Only Memory) 100C as memories. The optical network controller 100 includes a network I / F (interface) 100D and an HDD (Hard Disk Drive) 100E. Instead of the HDD (Hard Disk Drive) 100E, an SSD (Solid State Drive) may be adopted.

[0028] The optical network controller 100 may include at least one of an input I / F 100F, an output I / F 100G, an input / output I / F 100H, and a drive device 100I as required. From the CPU 100A to the drive device 100I, they are connected to each other by an internal bus 100J. That is, the optical network controller 100 can be realized by a computer.

[0029] An input device 710 is connected to the input I / F 100F. Examples of the input device 710 include a keyboard, a mouse, a touch panel, etc. A display device 720 is connected to the output I / F 100G. Examples of the display device 720 include a liquid crystal display. A semiconductor memory 730 is connected to the input / output I / F 100H. Examples of the semiconductor memory 730 include a USB (Universal Serial Bus) memory, a flash memory, etc. The input / output I / F 100H reads an optical transmission path characteristic estimation program stored in the semiconductor memory 730. The input I / F 100F and the input / output I / F 100H are provided with, for example, a USB port. The output I / F 100G is provided with, for example, a display port.

[0030] A portable recording medium 740 is inserted into the drive device 100I. Examples of the portable recording medium 740 include removable disks such as a CD (Compact Disc)-ROM and a DVD (Digital Versatile Disc). The drive device 100I reads an optical transmission path characteristic estimation program recorded on the portable recording medium 740. The network I / F 100D is provided with, for example, a LAN port, a communication circuit, etc. The communication circuit includes either or both of a wired communication circuit and a wireless communication circuit. The network I / F 100D is connected to the operation terminal 10 and the nodes #1, ···, #5.

[0031] The optical transmission path characteristic estimation program stored in at least one of the ROM 100C, the HDD 100E, and the semiconductor memory 730 is temporarily stored in the RAM 100B by the CPU 100A. The optical transmission path characteristic estimation program recorded on the portable recording medium 740 is temporarily stored in the RAM 100B by the CPU 100A. By executing the stored optical transmission path characteristic estimation program by the CPU 100A, the CPU 100A realizes various functions described later and executes an optical transmission path characteristic estimation method including various processes described later. Note that the optical transmission path characteristic estimation program may conform to the flowchart described later.

[0032] Referring to FIGS. 4 and 5, the functional configuration of the optical network controller 100 according to the first embodiment will be described.

[0033] As shown in FIG. 4, the optical network controller 100 includes a storage unit 110, a processing unit 120, and a communication unit 130. The storage unit 110 can be realized by either one or both of the above-described RAM 100B and HDD 100E. The processing unit 120 can be realized by the above-described CPU 100A. The communication unit 130 can be realized by the above-described network I / F 100D.

[0034] The storage unit 110, the processing unit 120, and the communication unit 130 are connected to each other. The storage unit 110 includes a network information storage unit 111. The processing unit 120 includes an identification unit 121, an acquisition unit 122, a calculation unit 123, and an estimation unit 124.

[0035] The network information storage unit 111 stores network information. The network information represents the operation state of an optical communication service using the optical network NW, as shown in FIG. 5. For example, the wavelength λ represents any wavelength in the C band (Conventional Band) with a wavelength range of 1530 nm (nanometers) to 1565 nm. Instead of the C band, a wavelength in the L band (Long Band) with a long wavelength range of 1565 nm to 1625 nm may be adopted for the wavelength λ.

[0036] In ch.1 (channel 1), which is the lowest wavelength of the C band, among the transmission sections from node #1 to node #5, the individual section from node #1 to node #2 is used to provide an optical communication service to customers. Therefore, the individual section from node #1 to node #2 corresponds to an in-service operation section. The in-service operation section is an example of the first section.

[0037] On the other hand, the individual sections from Node #2 to Node #5 are not utilized. That is, no optical communication service is provided to customers in this individual section. Therefore, the individual section from Node #2 to Node #5 corresponds to an out-of-service operation section. The out-of-service operation section is an example of the second section. Since ch.2 to ch.N are basically the same as ch.1, detailed description is omitted. In this way, the network information storage unit 111 stores network information in which in-service operation sections and out-of-service operation sections are mixed.

[0038] Returning to FIG. 4, when the specifying unit 121 detects an estimation instruction transmitted from the operation terminal 10, it refers to the network information and specifies all channels from ch.1 to ch.N used in the optical network NW. When the specifying unit 121 specifies all channels from ch.1 to ch.N, it selects any one channel from ch.1 to ch.N and specifies the measurement section of the PMD. For example, when ch.1 is selected, the specifying unit 121 specifies the in-service operation section from Node #1 to Node #2 and the out-of-service operation section from Node #2 to Node #5.

[0039] When the specifying unit 121 specifies the in-service operation section and the out-of-service operation section in the selected ch.1, it also specifies the in-service operation section and the out-of-service operation section in the remaining ch.2 to ch.N in the same way. Thereby, the specifying unit 121 specifies all in-service operation sections and all out-of-service operation sections.

[0040] The acquisition unit 122 acquires the PMD value. For example, in the service operation period from node #1 to node #2 in ch.1, the node #2 receives the signal light transmitted from node #1. Therefore, the acquisition unit 122 can acquire the PMD value from the measuring instrument M2 of node #2. On the other hand, in the non-service operation period from node #2 to node #5 in ch.1, the signal light is not propagating. Therefore, the acquisition unit 122 temporarily sets (or stretches) an optical path in ch.1 in the non-service operation period from node #2 to node #5. As a result, node #5 can receive the signal light transmitted from node #2, and the acquisition unit 122 can acquire the PMD value from the measuring instrument M5 of node #5.

[0041] The calculation unit 123 calculates the average value of the PMD values. For example, when ch.1 is specified, the calculation unit 123 calculates the square root of the sum of the square of the first PMD value, which is the PMD value acquired from the measuring instrument M2, and the square of the second PMD value, which is the PMD value acquired from the measuring instrument M5, as the wavelength-specific average value of the PMD values. The calculation unit 123 calculates the wavelength-specific average value of the PMD values for each channel from ch.2 to ch.N in the same manner as ch.1. That is, the calculation unit 123 calculates N wavelength-specific average values corresponding to the number of channels of the PMD values. After calculating the N wavelength-specific average values, the calculation unit 123 divides the sum of the N wavelength-specific average values by the number of channels. That is, the calculation unit 123 calculates the simple average (or arithmetic mean) of the N wavelength-specific average values. Thereby, the calculation unit 123 can calculate the average value of the PMD values from node #1 to node #5.

[0042] Based on the Maxwell distribution with the fixed occurrence probability of the worst value of the PMD value and the average value of the PMD value, the estimation unit 124 estimates the worst value of the PMD value as a constant k times the average value of the PMD value. The constant k corresponds to the ratio of the maximum value to the average value of the PMD value described in Table 9-2 of ITU-T Recommendation G.680 (see also Patent Document 1 described above). Details such as the Maxwell distribution used by the estimation unit 124 when estimating the worst value of the PMD value will be described later.

[0043] Referring to FIGS. 6 to 9, the operation of the optical network controller 100 according to the first embodiment will be described.

[0044] First, as shown in FIG. 6, the specifying unit 121 waits until it detects an estimation instruction (step S1: NO). The estimation instruction is an instruction for requesting the optical network controller 100 to estimate the worst value of the PMD value. When the estimation instruction is detected (step S1: YES), the specifying unit 121 specifies a channel and a measurement interval (step S2). Specifically, the specifying unit 121 refers to the network information and specifies all channels from ch.1 to ch.N used in the optical network NW. Further, when specifying all channels from ch.1 to ch.N, the specifying unit 121 specifies the service operation middle section and the service operation outside section for each channel from ch.1 to ch.N as the measurement interval.

[0045] After specifying the channel and the measurement interval, the specifying unit 121 outputs a measurement instruction (step S3). The measurement instruction is an instruction for requesting the measuring instrument M2, the measuring instrument M5, etc. to measure the PMD value. For example, when all channels from ch.1 to ch.N are specified, the specifying unit 121 selects ch.1 with the minimum wavelength, and also selects the service operation middle section and the service operation outside section in the selected ch.1. In this embodiment, the specifying unit 121 selects the individual section from node #1 to node #2 as the service operation middle section. Further, the specifying unit 121 selects the individual section from node #2 to node #5 as the service operation outside section.

[0046] When the specifying unit 121 selects ch.1 and the service operation middle section, it outputs a measurement instruction to the measuring instrument of the end node located at the end of the service operation middle section. In this embodiment, the specifying unit 121 outputs a measurement instruction to the measuring instrument M2 of node #2 located at the end of the service operation middle section.

[0047] Also, when the specific unit 121 selects ch.1 and the out-of-service interval, it sets ch.1 to any one of the digital coherent transmitters Tx included in the optical transmitter T2 of node #2, and sets ch.1 to any one of the digital coherent receivers Rx included in the optical receiver R5 of node #5. After the setting, the specific unit 121 temporarily sets a logical optical path in the out-of-service interval from node #2 to node #5. When the optical path is set, the specific unit 121 outputs a measurement instruction to the measuring instrument of the terminal node located at the end of the out-of-service interval. In this embodiment, the specific unit 121 outputs a measurement instruction to the measuring instrument M5 of node #5 located at the end of the out-of-service interval.

[0048] When the specific unit 121 outputs a measurement instruction, the acquisition unit 122 acquires the PMD value (step S4). As described above, when the specific unit 121 outputs a measurement instruction to the measuring instrument M2 of node #2, as shown in Fig. 7(a), the acquisition unit 122 acquires the PMD value from the measuring instrument M2. When the specific unit 121 outputs a measurement instruction to the measuring instrument M5 of node #5, as shown in Fig. 7(b), the acquisition unit 122 acquires the PMD value from the measuring instrument M5. When the specific unit 121 sets an optical path in the out-of-service interval, the acquisition unit 122 deletes the optical path after acquiring the PMD value and returns to the original standby state before the optical path setting.

[0049] When the acquisition unit 122 acquires the PMD value, the calculation unit 123 calculates the average value of the PMD values (step 5). For example, as described above, when the acquisition unit 122 acquires the first PMD value, which is the PMD value in the in-service interval of ch.1, and the second PMD value, which is the PMD value in the out-of-service interval, the calculation unit 123 calculates the wavelength-specific average value of the PMD values in ch.1 according to the following formula. Thereby, the average value of the PMD values in the transmission interval from node #1 to node #5 in ch.1 is calculated. <Formula> Wavelength-specific average value = √((First PMD value) 2 +(Second PMD value) 2 )

[0050] When the calculation unit 123 calculates the wavelength - average value of the PMD value in ch.1, it calculates the wavelength - average value of the PMD value in the same way as ch.1 from ch.2 to ch.N. For example, when the specifying unit 121 selects ch.N with the maximum wavelength and outputs a measurement instruction to the measuring instrument M3 of node #3, as shown in Fig. 8(a), the acquisition unit 122 acquires the PMD value from the measuring instrument M3. When the specifying unit 121 outputs a measurement instruction to the measuring instrument M5 of node #5, as shown in Fig. 8(b), the acquisition unit 122 acquires the PMD value from the measuring instrument M5. Thereby, the calculation unit 123 can calculate the wavelength - average value of the PMD value in ch.N. In this way, the calculation unit 123 calculates not only the wavelength - average value of the PMD value in ch.1 for the transmission section from node #1 to node #5, but also the wavelength - average value of the PMD value in all of ch.2 to ch.N.

[0051] When the calculation unit 123 calculates the wavelength - average value of the PMD value for all channels from ch.12 to ch.N for the transmission section from node #1 to node #5, it calculates the average value of the PMD values (i.e., the total average value). Specifically, the calculation unit 123 calculates the simple average of N wavelength - average values. Thereby, the calculation unit 123 can calculate the average value of the PMD value in the transmission section from node #1 to node #5.

[0052] When the average value of the PMD values is calculated, the estimation unit 124 estimates the worst value of the PMD value (step S6) and ends the process. Here, as shown in Fig. 9, the estimation unit 124 estimates the worst value X of the PMD value based on the average value μ of the PMD value and the Maxwell distribution in which the probability P of the occurrence of the worst value of the PMD value of the optical transmission line is fixed. max Here, when the PMD value varies temporally due to fluctuations in the optical transmission line (e.g., polarization rotation by the optical fiber 20), its statistical distribution (probability density distribution) can be theoretically approximated by the Maxwell distribution.

[0053] In the Maxwell distribution, when the average value μ of the PMD value is determined, the curve shape of the cumulative distribution function Gf is uniquely determined. Also, in the Maxwell distribution, when the probability P is fixed, the value of the inverse function of the survival function of the Maxwell distribution (i.e., the worst value X max ) of the PMD value is a constant multiple of the average value μ. The estimation unit 124 utilizes these properties to simply estimate the worst value of the PMD value in the transmission intervals from node #1 to node #5 as a constant k times (e.g., k = 3, etc.) of the average value μ.

[0054] In this way, the optical network controller 100 according to the first embodiment can estimate the worst value of the PMD value of the optical transmission paths from node #1 to node #5 even when the in-service intervals and out-of-service intervals are mixed.

[0055] (Second Embodiment) Subsequently, referring to FIGS. 10 to 12, the second embodiment of the present case will be described. Note that in FIG. 10, some processes overlapping with the flowchart shown in FIG. 6 are omitted. The same applies to the flowcharts of the embodiments described later. In the second embodiment, by limiting the channels selected by the specifying unit 121, the number of calculated average values of the PMD value is reduced. As a result, for example, the processing load of the CPU 100A is decreased, and the power consumption of the optical network controller 100 is suppressed.

[0056] First, as shown in FIG. 10, when the process of step S2 ends, the specifying unit 121 counts the number of individual intervals (step S11). More specifically, as shown in FIG. 11, the specifying unit 121 counts the number of individual intervals out of service for each of all the channels from ch.1 to ch.N that it has specified. For example, the specifying unit 121 counts the number of individual intervals for ch.1 as 1. Also, the specifying unit 121 counts the number of individual intervals as 2 for any one of ch.4 to ch.N - 1 (not shown).

[0057] When counting the number of individual intervals, the specifying unit 121 selects the channel with the minimum number (step S12). In the present embodiment, since the minimum number of individual intervals is 1, for example, the specifying unit 121 selects ch.1 with the minimum wavelength. Note that the specifying unit 121 may select ch.N with the maximum wavelength. When selecting the channel with the minimum number, the specifying unit 121 outputs a measurement instruction in the same manner as the process of step S3 (step S13). Thereby, the acquisition unit 122 acquires the PMD value in the same manner as the process of step S4 (step S14). That is, when the specifying unit 121 selects ch.1, the acquisition unit 122 acquires the PMD value from each of the measuring instruments M2 and M5.

[0058] Here, the specifying unit 121 determines whether or not it has exceeded a predetermined threshold bandwidth (step S15). For example, when the channels from ch.1 to ch.N correspond to the C band, one-eighth of the C band can be adopted as the predetermined threshold bandwidth. As shown in FIG. 12, when the average value AVR1 of the PMD values of the entire C band, the average value AVR2 of the PMD values of one-half of the C band, and the average value AVR4 of the PMD values of one-fourth of the C band are calculated, they become near a specific numerical value α.

[0059] On the other hand, when the average value AVR8 of the PMD values of one-eighth of the C band is calculated, large variations occur. That is, if less than one-eighth of the C band is adopted, the calculation accuracy of the average value of the PMD values may decrease. For this reason, in the second embodiment, the specifying unit 121 determines whether or not it has exceeded one-eighth of the C band. Thereby, a decrease in the calculation accuracy of the average value of the PMD values is suppressed.

[0060] When it has not exceeded the predetermined threshold bandwidth (step S15: NO), the specifying unit 121 repeats the processes of steps S12 to S14. Thereby, for example, the specifying unit 121 selects ch.2 with the next minimum wavelength for which the number of individual intervals is 1, and the acquisition unit 122 acquires the PMD value. That is, when the specifying unit 121 selects ch.2, the acquisition unit 122 acquires the PMD value from each of the measuring instruments M2 and M5. In this way, the processes of steps S12 to S14 are repeated until the predetermined threshold bandwidth is exceeded.

[0061] When the bandwidth exceeds a predetermined threshold (step S15: YES), the calculation unit 123 executes the processes of steps S5 and S6 in the same manner as in the first embodiment. As a result, the worst value of the PMD value is estimated. Thus, according to the second embodiment, even if the selection of channels is partially limited, the optical network controller 100 can accurately estimate the worst value of the PMD value.

[0062] (Third Embodiment) Subsequently, with reference to FIGS. 13 to 17, the third embodiment of the present invention will be described. The optical network controller 100 according to the third embodiment can estimate the worst value of the PMD value by avoiding the setting of the optical path described in the first embodiment. Thereby, for example, the use of the digital coherent receiver Rx and the digital coherent transmitter Tx can be avoided, and the lifetimes of the digital coherent receiver Rx and the digital coherent transmitter Tx can be suppressed.

[0063] First, as shown in FIG. 13, when the acquisition unit 122 executes the process of step S4, the calculation unit 123 calculates the average value of the PMD values in the common individual section (step S21). The average value of the PMD values in the common individual section is an example of the first polarization characteristic average value. For example, as shown in FIG. 14, the individual section Z1 from node #1 to node #2 during service operation is common to ch.1 and ch.2. Here, the acquisition unit 122 acquires the PMD value of ch.1 and the PMD value of ch.2 from the measuring instrument M2 at node #2 by the process of step S4. Therefore, the calculation unit 123 calculates the simple average of these two PMD values as the average value of the PMD values.

[0064] When calculating the average value of the PMD values of the common individual intervals, the calculation unit 123 calculates the average value of the PMD values of the combined individual intervals (step S22). The average value of the PMD values of the combined individual intervals is an example of the second polarization characteristic average value. For example, as shown in FIG. 15, the calculation unit 123 identifies the individual intervals Z2a and Z2b that have no channel overlap and are adjacent to each other as service operation intervals as the combined individual intervals. When the combined individual intervals are identified, the calculation unit 123 calculates the square root of the sum of the square of the average value of the individual interval Z2a and the square of the PMD value of the individual interval Z2b. The calculation unit 123 uses this calculated square root as the average value of the PMD values of the combined individual intervals.

[0065] When calculating the average value of the PMD values of the combined individual intervals, the calculation unit 123 determines whether there are any combinable intervals (step S23). That is, it determines whether there are any individual intervals that have no channel overlap and are adjacent to each other as service operation intervals. For example, as shown in FIG. 15, when there is an individual interval Z4 that has no channel overlap and is adjacent to each other as service operation intervals, the calculation unit 123 determines that there is a combinable interval (step S23: NO). In this case, the calculation unit 123 repeats the processes of steps S21 and S22.

[0066] As a result, as shown in FIG. 16, the calculation unit 123 newly calculates the simple average of the average value of the PMD values of the combined individual intervals described above and the PMD value of ch.N as the average value of the PMD values of the common individual intervals for the individual interval Z3 including the individual interval Z1. Also, as shown in FIG. 17, the calculation unit 123 newly identifies the individual intervals Z3 and Z4 that have no channel overlap and are adjacent to each other as service operation intervals as the combined individual intervals. When the combined individual intervals are identified, the calculation unit 123 calculates the square root of the sum of the square of the average value of the individual interval Z3 and the square of the PMD value of the individual interval Z4. The calculation unit 123 uses this calculated square root as the average value of the PMD values of the newly combined individual intervals.

[0067] When there is no channel overlap and there are no individual sections that are adjacent to each other as service operation sections, the calculation unit 123 determines that there is no combinable section (step S23: YES). For example, as shown in FIG. 17, when there is no channel overlap and there is no combinable individual section adjacent to the individual section Z4 as the service operation section, the calculation unit 123 determines that there is no combinable section. Thereby, the average value of the PMD values from node #1 to node #5 is specified.

[0068] When there is no combinable section, the calculation unit 123 determines whether there is a non-service operation section in the transmission direction (step S24). In the present embodiment, as shown in FIG. 17, there is an individual section Z4 representing the service operation section from node #3 to node #5. Therefore, the calculation unit 123 determines that there is no non-service operation section in the transmission direction (step S24: NO), and skips the processes of subsequent steps S25 to S27. Thereby, the estimation unit 124 executes the process of step S6.

[0069] If there is a node #6 adjacent to node #5 in the transmission direction and the individual section from node #5 to node #6 is a non-service operation section, the calculation unit 123 determines that there is a non-service operation section in the transmission direction (step S24: YES). In this case, since it is a non-service operation section, the acquisition unit 122 cannot acquire the PMD value from the measuring instrument of node #6.

[0070] Therefore, the acquisition unit 122 temporarily sets an optical path, for example, in ch. 3 in the non-service operation section from node #5 to node #6 (step S25). Thereby, since the signal light transmitted from node #5 is received by node #6, the acquisition unit 122 acquires the PMD value from the measuring instrument of node #6 (step S26). When the PMD value is acquired, based on the average value of the PMD values in the combined individual section from node #1 to node #5 calculated in the process of step S22 and the PMD value acquired in the process of step S26, the calculation unit 123 calculates the average value of the PMD values.

[0071] In this case, the calculation unit 123 calculates the average value of the PMD values by the square root of the sum of squares. When the average value of the PMD values is calculated, the estimation unit 124 executes the process of step S6. Thus, according to the third embodiment, the optical network controller 100 may be able to estimate the worst value of the PMD value by avoiding the optical path setting described in the first embodiment. Thereby, for example, the use of the digital coherent receiver Rx and the digital coherent transmitter Tx can be avoided, and the lifetimes of the digital coherent receiver Rx and the digital coherent transmitter Tx can be suppressed. Also, when there is an out-of-service section in the transmission direction, the optical network controller 100 temporarily sets an optical path and calculates the average value of the PMD values in the same manner as in the first embodiment. Thereby, the optical network controller 100 can estimate the worst value of the PMD value.

[0072] (Fourth Embodiment) Subsequently, with reference to FIGS. 18 and 19, the fourth embodiment of the present case will be described. The optical network controller 100 according to the fourth embodiment collects the polarization fluctuation speed and calculates the average value of the PMD values based on the collected polarization fluctuation speed. By calculating the average value of the PMD values based on the polarization fluctuation speed, the optical network controller 100 can improve the calculation accuracy of the average value of the PMD values.

[0073] First, as shown in FIG. 18, the processing unit 120 of the optical network controller 100 further includes a request unit 125 and a collection unit 126. When the specifying unit 121 detects an estimation instruction, the request unit 125 requests the measuring device Mx (see FIG. 1) provided in the optical receiver R3 of, for example, node #3 to measure the polarization fluctuation speed as described in the first embodiment.

[0074] The collection unit 126 collects the polarization fluctuation speed measured by the measuring device Mx, and associates the collected polarization fluctuation speed with the network information. For example, the collection unit 126 associates the polarization fluctuation speed with the interval during service operation for each channel. Thereby, the specifying unit 121 that refers to the network information can determine whether polarization fluctuations frequently occur in the interval during service operation in which the signal light propagates.

[0075] Here, as shown in FIG. 19, in the process of step S1, when the specifying unit 121 detects an estimation instruction, the request unit 125 requests measurement of the polarization fluctuation speed (step S41). When the measuring device Mx is requested to measure the polarization fluctuation speed, it measures the polarization fluctuation speed. Thereby, the collection unit 126 collects the polarization fluctuation speed (step S42). After collecting the polarization fluctuation speed, in the process of step S2, the specifying unit 121 specifies the channel and the measurement interval based on the polarization fluctuation speed associated with the network information by the collection unit 126.

[0076] More specifically, the specifying unit 121 determines whether polarization fluctuations frequently occur in the interval during service operation in which the signal light propagates based on the amount of polarization fluctuation. This amount of polarization fluctuation may be the average value of the polarization fluctuation speeds measured within a certain time, or may be the cumulative value of the polarization fluctuation time above the threshold speed measured within a certain time.

[0077] If the amount of polarization fluctuation exceeds the threshold amount of fluctuation, the specifying unit 121 determines that polarization fluctuations frequently occur, and specifies the channel and the measurement interval of the amount of polarization fluctuation that exceeds the threshold amount of fluctuation. If the calculation unit 123 calculates the average value of the PMD values based on the channel and the measurement interval specified in this way, the average value of the PMD values can be calculated with higher accuracy compared to the case where polarization fluctuations do not frequently occur. Thereby, the optical network controller 100 can improve the estimation accuracy of the worst value of the PMD value.

[0078] (Fifth Embodiment) Next, referring to FIG. 20, the fifth embodiment of the present case will be described. As described in the above embodiments, the acquisition unit 122 acquires PMD values. However, depending on the set of PMD values acquired by the acquisition unit 122, it may not conform to the Maxwell distribution. For example, when the number of PMD values acquired by the acquisition unit 122 is small, the set of PMD values is small, so it may not follow the Maxwell distribution. In this case, the optical network controller 100 may not be able to accurately estimate the worst value of the PMD value based on the Maxwell distribution.

[0079] Therefore, the acquisition unit 122 uses a goodness-of-fit test to determine whether the set of PMD values conforms to the Maxwell distribution. If the set of PMD values does not conform to the Maxwell distribution, the acquisition unit 122 may discard the PMD value, or may acquire the PMD value until it passes the goodness-of-fit test. As the goodness-of-fit test, for example, a known Kolmogorov-Smirnov test (K-S test) can be used.

[0080] For example, as shown in FIG. 20, as a result of comparing the cumulative distribution function Gs of the PMD values acquired by the acquisition unit 122 with the cumulative distribution function Gf of the Maxwell distribution, there may be a significant maximum statistical difference D in a part between the cumulative distribution function Gs and the cumulative distribution function Gf. In such a case, the acquisition unit 122 acquires PMD values until it passes the K-S test. Thereby, the calculation unit 123 can accurately calculate the average value of the PMD values. As a result, the estimation unit 124 can accurately estimate the worst value of the PMD value.

[0081] (Sixth Embodiment) Next, referring to FIGS. 21 to 23, the sixth embodiment of the present case will be described. The optical network controller 100 according to the sixth embodiment selects signal types such as modulation methods, baud rates, and transmission capacities based on the worst PMD values estimated in the first to fifth embodiments. As described in the first to fifth embodiments, even if there are mixed service operation intervals and non-service operation intervals, the optical network controller 100 can estimate the worst PMD value. Therefore, the optical network controller 100 can select an appropriate signal type based on the estimated worst value regardless of the design value of the PMD value.

[0082] First, as shown in FIG. 21, the processing unit 120 of the optical network controller 100 further includes a selection unit 127. The selection unit 127 selects a signal type based on the worst PMD value estimated by the estimation unit 124. Also, as shown in FIG. 22, when the estimation unit 124 estimates the worst PMD value by the process of step S6, the selection unit 127 selects a signal type (step S51) and ends the process.

[0083] Thereby, as shown in FIG. 23, for example, even when the worst PMD value allowable by design is estimated to be 70 ps (picoseconds), the estimation unit 124 may estimate 40 ps as the worst PMD value. In such a case, the selection unit 127 can select signal type IDs "1" and "2" whose worst allowable PMD value is 50 ps. At this time, it is desirable for the selection unit 127 to select the signal type ID "2" that realizes the maximum transmission capacity. Note that the selection unit 127 may select a combination of modulation method, baud rate, and transmission capacity associated with the signal type ID "2", or may select at least one of them.

[0084] As a result, for example, the optical network controller 100 can reduce the number of combinations of the digital coherent transmitter Tx and the digital coherent receiver Rx required for transmitting and receiving the optical signal from two pairs to one pair, or from three pairs to two pairs. As a result, the power consumption of the digital coherent transmitter Tx and the digital coherent receiver Rx can be reduced.

[0085] (Seventh Embodiment) Subsequently, with reference to FIGS. 24 to 28, the seventh embodiment of the present invention will be described. As shown in FIG. 24, the optical network NW includes a node #T, a plurality of nodes #1, ···, #5 described in the first embodiment, and a node #R. The node #T is an example of a transmitting node and includes a transponder that transmits an optical signal. The node #R is an example of a receiving node and includes a transponder that receives an optical signal. The node #T is arranged at one end of the optical network NW. The node #R is arranged at the other end of the optical network NW. The nodes #1, ···, #5 are arranged as relay nodes between the node #T and the node #R.

[0086] The optical network controller 100 according to the seventh embodiment acquires and accumulates the Q value of the optical signal after propagating through the optical transmission path corresponding to the entire transmission section from one end to the other end of the optical network NW from the node #R. The node #R includes a measuring device M6 that measures the PreFEC BER (Pre Forward Error Correction Bit Error Rate) and converts the measured PreFEC BER into a Q value based on a known conversion method. Therefore, the optical network controller 100 can acquire and accumulate the Q value from the measuring device M6.

[0087] When the optical network controller 100 accumulates the Q value, it calculates the change amount ΔQ of the Q value over a certain period, and based on the change amount ΔQ, estimates the transmission penalty that varies temporally according to polarization characteristics such as PMD and PDL. More specifically, the optical network controller 100 estimates the OSNR penalty, which is an example of the transmission penalty, based on the change amount ΔQ and the OSNR (Optical Signal-to-Noise Ratio)-Q characteristic. Although details will be described later, the OSNR-Q characteristic is a graph representing the correlation between the Q value and the OSNR.

[0088] Note that the Q value is an example of a signal quality indicator, and the transmission penalty is an example of a characteristic value that varies temporally according to polarization characteristics. The signal quality indicator is not limited to the Q value and may be the PreFEC BER (Pre Forward Error Correction Bit Error Rate). The PreFEC BER is the bit error rate before forward error correction. For example, instead of the measuring instrument M6 converting the PreFEC BER to the Q value, the optical network controller 100 may acquire the PreFEC BER and convert the acquired PreFEC BER to the Q value.

[0089] Referring to FIG. 25, the functional configuration of the optical network controller 100 according to the seventh embodiment will be described. As shown in FIG. 7, the storage unit 110 includes a measurement value storage unit 112. Further, the processing unit 120 includes an acquisition unit 122, a calculation unit 123, an estimation unit 124, and a design unit 128.

[0090] The acquisition unit 122 acquires the Q value from the measuring instrument M6 of node #R. For example, the acquisition unit 122 acquires the Q value at regular intervals such as 15 minutes or 1 hour over a long period such as several days or several months. When the acquisition unit 122 acquires the Q value, it stores the Q value in the measurement value storage unit 112. As a result, the measurement value storage unit 112 stores the Q values that change in time series. In this way, time-series Q values that change over time are accumulated in the optical network controller 100.

[0091] In addition, when the acquisition unit 122 acquires the PreFEC BER from the measuring instrument M6, it may convert the PreFEC BER into a Q value based on a known conversion method and store the Q value in the measurement value storage unit 112. As the known conversion method, for example, the conversion method disclosed in Japanese Patent Application Laid-Open No. 2018-082344 can be referred to.

[0092] The calculation unit 123 extracts Q values for a certain period (for example, 3 days, 1 week, etc.) from the measurement value storage unit 112 and calculates the change amount ΔQ of the Q values over the certain period. Although details will be described later, when the calculation unit 123 extracts the Q values, it generates a distribution of the Q values (for example, a frequency distribution table or a histogram) and calculates the average value of the Q values. When the calculation unit 123 calculates the average value of the Q values, it fits the average value of the Q values to a Maxwell distribution (see FIG. 9) and calculates the worst value of the Q values as the change amount ΔQ of the Q values. Thus, when the Q value changes over time, its statistical distribution (probability density distribution) can theoretically approximate a Maxwell distribution.

[0093] The estimation unit 124 estimates the transmission penalty based on the change amount ΔQ calculated by the calculation unit 123. As described above, the estimation unit 124 estimates the OSNR penalty corresponding to the change amount ΔQ based on the change amount ΔQ and the OSNR-Q characteristic. When the estimation unit 124 estimates the OSNR penalty, it applies the OSNR penalty to the design unit 128. Thus, the estimation unit 124 estimates the OSNR penalty caused by the polarization characteristic using the Q value without using the polarization characteristic value with a large measurement error (specifically, the PMD value or the PDL value). Thereby, the estimation accuracy of the OSNR penalty is improved compared to the case of using the polarization characteristic value.

[0094] The design unit 128 calculates the reachability of the signal light based on the input power of the signal light input to node #R and the power loss of the signal light generated in the section from, for example, node #4 to node #5 (hereinafter referred to as span loss). The input power is an example of a power index, and the span loss is an example of a loss index. More specifically, the design unit 128 estimates the OSNR and transmission penalty for each time based on the input power and span loss at each time, and simulates the Q value at each time of the signal light after transmitting through the optical network NW. The transmission penalty estimated by the design unit 128 includes not only the PDL penalty caused by PDL and the PMD penalty caused by PMD, but also, for example, the penalty caused by wavelength dispersion.

[0095] Here, when simulating the Q value, the design unit 128 may simulate the Q value including information such as the network topology of the optical network NW, the span length, and the performance information of each device such as node #T, node #R, and nodes #1, ··· #5. When the design unit 128 simulates the Q value at each time, it outputs the simulated Q value at each time to the calculation unit 123. Thereby, the calculation unit 123 calculates the time difference of the Q value at each time as the correction value of the Q value. The correction value of the Q value is an example of the signal quality change amount and corresponds to the influence amount of the input power and the span loss on the Q value. The calculation unit 123 calculates a new Q value obtained by removing the correction value of the Q value from the Q value as the measured value acquired by the acquisition unit 122 as the corrected Q value. The corrected Q value is an example of a new signal quality index. Note that the calculation unit 123 may separately calculate the influence amount of the input power on the Q value and the influence amount of the span loss on the Q value as the signal quality change amount.

[0096] With reference to FIGS. 26 to 28, the operation of the optical network controller 100 according to the seventh embodiment will be described.

[0097] First, as shown in FIG. 26, the acquisition unit 122 waits until a estimation instruction is detected (step S61: NO). The estimation instruction is an instruction to request the estimation of the transmission penalty to the optical network controller 100. When the estimation instruction is detected (step S61: YES), the acquisition unit 122 acquires the Q value (step S62). For example, the acquisition unit 122 periodically acquires the Q value at regular intervals such as 15 minutes or 60 minutes. When the acquisition unit 122 acquires the Q value, it stores the Q value in the measurement value storage unit 112. As a result, as shown in FIG. 27, the measurement value storage unit 112 stores the time-series Q values 91 that change according to the passage of time.

[0098] When the acquisition unit 122 acquires the Q value and stores it in the measurement value storage unit 112, the calculation unit 123 generates the distribution of the Q value (step S63). More specifically, the calculation unit 123 extracts the Q values for a certain period from the measurement value storage unit 112 and generates the distribution of the Q value as shown in FIG. 28(a).

[0099] When the distribution of the Q value is generated, the calculation unit 123 calculates the change amount ΔQ of the Q value (step S64). More specifically, the calculation unit 123 calculates the average value of the Q values based on the distribution of the Q values, calculates the worst value of the Q values by fitting the average value of the Q values to the Maxwell distribution, and specifies the worst value of the Q values as the change amount ΔQ of the Q value as shown in FIG. 28(a).

[0100] When the calculation unit 123 calculates the change amount ΔQ of the Q value, the estimation unit 124 estimates the transmission penalty (step S65). More specifically, as shown in FIG. 28(b), the estimation unit 124 estimates the OSNR penalty ΔOSNR corresponding to the change amount ΔQ as the transmission penalty based on the change amount ΔQ of the Q value calculated by the calculation unit 123 and the OSNR-Q characteristic 92. In this way, the transmission penalty of the signal quality due to the polarization characteristic varies due to the time change of the polarization state and appears as a change in the Q value. Therefore, by measuring the Q value and calculating backward from the change in the Q value, the estimation unit 124 can estimate the transmission penalty.

[0101] When estimating the transmission penalty, the estimation unit 124 applies the transmission penalty to the design unit 128 (step S66) and ends a series of processes. As described above, the design unit 128 estimates the PDL penalty and the PMD penalty, but the estimation unit 124 changes the PDL penalty and the PMD penalty to the transmission penalty. As a result, in the next reachability calculation, the design unit 128 can simulate the Q value based on the transmission penalty estimated by the estimation unit 124.

[0102] Therefore, the transmission penalty according to the present embodiment is suppressed to less than half compared to the transmission penalty as a fixed value designed according to the specification standard and the transmission penalty dynamically estimated based on polarization characteristics values such as PMD values and PDL values. Thus, in the present embodiment, by improving the accuracy of the transmission penalty, it is possible to reduce a wasteful margin for ensuring transmission quality.

[0103] (Eighth Embodiment) Subsequently, with reference to FIGS. 29 to 32, the eighth embodiment of the present case will be described. In FIG. 29, the same components as those of the optical network NW described with reference to FIG. 24 are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0104] First, as shown in FIG. 29, the node #R includes, in addition to the measuring instrument M6, a measuring instrument M7 that measures the input power of the signal light input to the node #R. The measuring instrument M7 measures the input power in synchronization with the measurement of the PreFEC BER by the measuring instrument M6. The optical network controller 100 can acquire and accumulate the input power from the measuring instrument M7. Further, the node #5 includes a measuring instrument M8 that measures the span loss generated in the section from the node #4 to the node #5. The measuring instrument M8 measures the span loss in synchronization with the measurement of the PreFEC BER by the measuring instrument M6. The optical network controller 100 can acquire and accumulate the span loss from the measuring instrument M8.

[0105] Note that, although not shown, each of Node #1 to Node #4 may also include a measuring device that measures span loss, similar to Node #5. In this case, the optical network controller 100 can acquire and accumulate the span loss from each measuring device of Node #1 to Node #4.

[0106] Subsequently, with reference to FIGS. 30 to 32, the operation of the optical network controller 100 according to the eighth embodiment will be described. Note that in FIG. 30, some processes overlapping with the flowchart shown in FIG. 26 are omitted.

[0107] As shown in FIG. 30, when the process of step S62 ends, the acquisition unit 122 acquires the input power and the span loss (step S71). More specifically, the acquisition unit 122 acquires the optical power from the measuring device M7 of Node #R and the span loss from the measuring device M8 of Node #5, in the same manner as the acquisition of the Q value. When the acquisition unit 122 acquires the input power and the span loss, it stores the acquired input power and span loss in the measurement value storage unit 112. As a result, as shown in FIG. 31(a), the measurement value storage unit 112 stores the time-series input power 93 that changes over time. Also, as shown in FIG. 31(b), the measurement value storage unit 112 stores the time-series span loss 94 that changes over time.

[0108] When the acquisition unit 122 acquires the input power and the span loss and stores them in the measurement value storage unit 112, the calculation unit 123 calculates the amount of influence on the Q value (step S72). More specifically, the calculation unit 123 extracts the Q value, the input power, and the span loss for a certain period from the measurement value storage unit 112, and outputs the extracted Q value, input power, and span loss to the design unit 128 for each time. As a result, the design unit 128 simulates the Q value of the signal light at each time after the optical network NW transmission based on the input power and the span loss. When the design unit 128 simulates the Q value at each time, it outputs the Q value at each time to the calculation unit 123. As a result, the calculation unit 123 calculates the time difference of the Q value at each time as the correction value of the Q value, thereby calculating the amount of influence on the Q value by the input power and the span loss.

[0109] Here, for example, as shown in Fig. 32(a), when the span loss changes, the OSNR changes in response to the change in the span loss. Specifically, when the span loss increases, the OSNR decreases. Conversely, when the span loss decreases, the OSNR increases. When the OSNR increases, as shown in Fig. 32(b), the Q value increases. Also, as shown in Fig. 32(c), when the input power of the signal light to node #R is small, the performance of node #R deteriorates compared to when the input power is large, so the Q value decreases. Thus, changes in the span loss and input power appear as changes in the Q value.

[0110] When calculating the amount of influence on the Q value, the calculation unit 123 corrects the Q value (step S73). More specifically, the calculation unit 123 corrects the Q value by removing the amount of influence on the Q value from the Q value as the measured value. By removing the amount of influence on the Q value from the Q value as the measured value, as shown in Fig. 31(c), the time-series Q value 91 before correction changes to the time-series Q value 95 after correction. The time-series Q value 95 after correction has the influence of changes in the input power and span loss removed. When the calculation unit 123 corrects the Q value, it generates the distribution of the Q value after correction by the processes of steps S63 and S64, and calculates the change amount ΔQ of the Q value after correction. Then, the estimation unit 124 estimates the transmission penalty based on the change amount ΔQ of the Q value after correction.

[0111] Thus, in the eighth embodiment, based on the amount of influence on the Q value such as the input power and span loss, the calculation unit 123 corrects the Q value. Specifically, the calculation unit 123 corrects the Q value by removing the amount of influence on the Q value from the Q value as the measured value. Then, the calculation unit 123 calculates the change amount ΔQ based on the Q value after correction, and the estimation unit 124 estimates the transmission penalty based on this change amount ΔQ. Thus, since the transmission penalty is estimated based on the Q value after correction, the estimation accuracy of the transmission penalty is improved compared to the case of the seventh embodiment.

[0112] As described above in detail are the preferred embodiments of the present invention. However, the present invention is not limited to the specific embodiments described, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

[0113] For example, when the acquisition unit 122 detects a change in the operating state such as an increase or decrease in the number of wavelengths in an optical communication service using a plurality of wavelengths provided by the optical network NW, the acquired Q value may be discarded and the Q value may be acquired again. Thereby, the influence on the Q value due to the change in the operating state is avoided, and the transmission penalty is accurately estimated. Also, when such a change in the operating state is detected, the acquisition unit 122 may calculate the difference between the Q values before and after the change in the operating state and correct the acquired Q value based on the difference. Even with such a configuration, the influence on the Q value due to the change in the operating state is avoided, and the transmission penalty is accurately estimated.

[0114] In addition, the following supplementary notes are disclosed regarding the above description. (Supplementary Note 1) An optical transmission path characteristic estimation device for estimating the polarization characteristic value of an optical path in which a first section during service operation and a second section outside service operation of an optical communication service using a plurality of wavelengths are mixed, based on information representing the operating state of the optical communication service, an acquisition unit that acquires a first polarization characteristic value for each of the plurality of wavelengths in the first section and a second polarization characteristic value for each of the plurality of wavelengths in the second section, and a calculation unit that calculates a wavelength-specific polarization characteristic value for each of the plurality of wavelengths of the optical path based on the first polarization characteristic value and the second polarization characteristic value. (Supplementary Note 2) The calculation unit calculates a polarization characteristic average value, which is the average value of the wavelength-specific polarization characteristic values, based on the sum of the wavelength-specific polarization characteristic values and the number of wavelengths of the plurality of wavelengths. The optical transmission path characteristic estimation device according to Supplementary Note 1, characterized in that. (Supplementary Note 3) An estimation unit that estimates the limit value as a constant multiple of the polarization characteristic average value based on a Maxwell distribution in which the occurrence probability of the limit value of the polarization characteristic value of the optical path is fixed and the polarization characteristic average value. The optical transmission path characteristic estimation device according to Supplementary Note 2, characterized in that. (Appendix 4) A specifying unit that counts the number of the second intervals in the optical path for each wavelength and specifies a part of the plurality of wavelengths until the threshold bandwidth is reached in ascending order of the number, and the acquisition unit acquires the first polarization characteristic value of the first interval corresponding to the part of the plurality of wavelengths specified by the specifying unit. The optical transmission path characteristic estimation device according to Appendix 1, characterized in that. (Appendix 5) An optical transmission path characteristic estimation device that estimates the polarization characteristic value of an optical path in which a first interval during service operation and a second interval outside service operation of an optical communication service using a plurality of wavelengths are mixed. An acquisition unit that acquires the first polarization characteristic value of each of the plurality of wavelengths in the first interval based on information indicating the operation state of the optical communication service, and based on the first polarization characteristic value common to the first intervals, calculates a first polarization characteristic average value that is the average value of the first polarization characteristic values, and based on the first polarization characteristic value of the combined interval obtained by combining adjacent first intervals and the first polarization characteristic average value, calculates a second polarization characteristic average value that is the average value of the first polarization characteristic values in the combined interval. When there is no second interval adjacent to the combined interval in the transmission direction of the signal light including any of the plurality of wavelengths, an estimation unit that estimates the limit value as a constant multiple of the second polarization characteristic average value based on a Maxwell distribution in which the occurrence probability of the limit value of the polarization characteristic value of the optical path is fixed and the second polarization characteristic average value. An optical transmission path characteristic estimation device having. (Appendix 6) A collection unit that collects the speed of polarization fluctuation occurring in the first interval, and a specifying unit that specifies the first interval and a part of the plurality of wavelengths in which the polarization fluctuation amount corresponding to the speed of the polarization fluctuation exceeds a threshold fluctuation amount. The acquisition unit acquires the first polarization characteristic value and the second polarization characteristic value of a part of the plurality of wavelengths in the first interval specified by the specifying unit, and the calculation unit calculates the polarization characteristic average value based on the first polarization characteristic value and the second polarization characteristic value. The optical transmission path characteristic estimation device according to Appendix 2, characterized in that. (Supplementary Note 7) The calculation unit determines, based on a goodness-of-fit test, whether the set of the first polarization characteristic values conforms to the cumulative distribution function of the Maxwell distribution. The acquisition unit acquires the first polarization characteristic values until the set conforms to the cumulative distribution function when the set does not conform to the cumulative distribution function. The optical transmission path characteristic estimation device according to Supplementary Note 3, characterized by the above. (Supplementary Note 8) The optical transmission path characteristic estimation device according to Supplementary Note 3, characterized by including a selection unit that selects a signal type of signal light using the plurality of wavelengths based on the limit value estimated by the estimation unit. (Supplementary Note 9) In an optical transmission system including a plurality of nodes having an optical device with a CDC function and a wavelength-variable optical transceiver, based on an instruction of the optical transmission path characteristic estimation device according to Supplementary Note 1, the wavelength of the optical transceiver and the path of the optical device with the CDC function are set, and the second polarization characteristic value is acquired. An optical transmission system characterized by the above. (Supplementary Note 10) An optical transmission path characteristic estimation method in which a computer estimates polarization characteristic values of an optical path in which a first section during service operation and a second section outside service operation of an optical communication service using a plurality of wavelengths are mixed. Based on information indicating an operation state of the optical communication service, first polarization characteristic values of each of the plurality of wavelengths in the first section are acquired, second polarization characteristic values of each of the plurality of wavelengths in the second section are acquired, and wavelength-specific polarization characteristic values of each of the plurality of wavelengths of the optical path are calculated based on the first polarization characteristic values and the second polarization characteristic values. An optical transmission path characteristic estimation method characterized by the above. (Supplementary Note 11) An optical transmission path characteristic estimation device that estimates a characteristic value that varies temporally according to the polarization characteristic of an optical transmission path including a plurality of nodes arranged from one end to the other end of an optical network. The device includes an acquisition unit that acquires a signal quality index of signal light after propagating through the optical transmission path from a receiving node arranged at the other end of the optical network, a calculation unit that calculates a quality change amount of the signal quality index over a certain period, and an estimation unit that estimates the characteristic value based on the quality change amount. (Supplementary Note 12) The optical transmission path characteristic estimation device according to Supplementary Note 11, characterized in that the calculation unit calculates the quality change amount based on an average value of the signal quality index and the Maxwell distribution. (Appended Note 13) When the acquisition unit detects a change in the operating state including an increase or decrease in the number of wavelengths in an optical communication service using a plurality of wavelengths provided by the optical network, the acquisition unit discards the acquired signal quality index and acquires the signal quality index again. The optical transmission path characteristic estimation device according to Appended Note 11 or 12, characterized in that. (Appended Note 14) When the acquisition unit detects a change in the operating state including an increase or decrease in the number of wavelengths in an optical communication service using a plurality of wavelengths provided by the optical network, the acquisition unit calculates a difference between the signal quality indexes before and after the change in the operating state, and corrects the acquired signal quality index based on the difference. The optical transmission path characteristic estimation device according to Appended Note 11 or 12, characterized in that. (Appended Note 15) The acquisition unit acquires a loss index representing the power loss of the signal light generated in the section from the second relay node arranged upstream of the first relay node to the first relay node from the first relay node arranged between one end and the other end of the optical network. The calculation unit calculates a new signal quality index obtained by dividing the signal quality change amount calculated based on the loss index for the fixed period by the signal quality index, and the estimation unit estimates the characteristic value based on the new signal quality index. The optical transmission path characteristic estimation device according to Appended Note 11 or 12, characterized in that. (Appended Note 16) The acquisition unit acquires a power index representing the input power of the signal light input to the receiving node from the receiving node. The calculation unit calculates a new signal quality index obtained by dividing the signal quality change amount calculated based on the power index for the fixed period by the signal quality index, and the estimation unit estimates the characteristic value based on the new signal quality index. The optical transmission path characteristic estimation device according to Appended Note 11 or 12, characterized in that. (Appended Note 17) The acquisition unit acquires a loss index representing the power loss of the signal light generated in the section from a second relay node arranged upstream of the first relay node to the first relay node from the first relay node arranged between one end and the other end of the optical network, acquires a power index representing the input power of the signal light input to the receiving node from the receiving node, the calculation unit calculates a new signal quality index obtained by removing, from the signal quality index, the amount of signal quality change calculated based on the loss index for the fixed period and the amount of signal quality change calculated based on the power index for the fixed period, and the estimation unit estimates the characteristic value based on the new signal quality index. The optical transmission path characteristic estimation device according to Appended Note 11 or 12, characterized in that (Appended Note 18) The signal quality index includes either the Q value of the signal light or the bit error rate before error correction of the signal light. The optical transmission path characteristic estimation device according to Appended Note 11 or 12, characterized in that (Appended Note 19) An optical transmission path characteristic estimation method in which a computer estimates a characteristic value that varies temporally according to the polarization characteristic of an optical transmission path including a plurality of nodes arranged from one end to the other end of an optical network, acquires a signal quality index of the signal light after propagating through the optical transmission path from a receiving node arranged at the other end of the optical network, calculates an amount of quality change for a fixed period of the signal quality index, and estimates the characteristic value based on the amount of quality change. The optical transmission path characteristic estimation method, characterized in that

Explanation of Signs

[0115] 10 Operation terminal 100 Optical network controller 110 Storage unit 111 Network information storage unit 112 Measurement value storage unit 120 Processing unit 121 Identification unit 122 Acquisition unit 123 Calculation unit 124 Estimation unit 125 Request unit 126 Collection unit 127 Selection unit 128 Design Department

Claims

1. An optical transmission path characteristic estimation device for estimating the polarization characteristic values of an optical path in which a first section during the service operation of an optical communication service using a plurality of wavelengths and a second section outside the service operation are mixed, an acquisition unit that acquires a first polarization characteristic value for each of the plurality of wavelengths in the first section and a second polarization characteristic value for each of the plurality of wavelengths in the second section based on information indicating the operation state of the optical communication service; a calculation unit that calculates a wavelength-specific polarization characteristic value for each of the plurality of wavelengths of the optical path based on the first polarization characteristic value and the second polarization characteristic value; An optical transmission path characteristic estimation device having the above.

2. The calculation unit calculates a polarization characteristic average value, which is an average value of the wavelength-specific polarization characteristic values, based on the sum of the wavelength-specific polarization characteristic values and the number of wavelengths of the plurality of wavelengths. The optical transmission path characteristic estimation device according to claim 1, characterized in that.

3. Based on a Maxwell distribution in which the occurrence probability of a limit value of the polarization characteristic value of the optical path is fixed and the polarization characteristic average value, it has an estimation unit that estimates the limit value as a constant multiple of the polarization characteristic average value. The optical transmission path characteristic estimation device according to claim 2, characterized in that.

4. Including a specifying unit that counts the number of the second sections in the optical path for each wavelength and specifies a part of the plurality of wavelengths until the threshold bandwidth is reached in ascending order of the number, The acquisition unit acquires the first polarization characteristic value of the first section corresponding to a part of the plurality of wavelengths specified by the specifying unit. The optical transmission path characteristic estimation device according to claim 1, characterized in that.

5. An optical transmission path characteristic estimation device for estimating the polarization characteristic values of an optical path in which a first section during the service operation of an optical communication service using a plurality of wavelengths and a second section outside the service operation are mixed, an acquisition unit that acquires a first polarization characteristic value for each of the plurality of wavelengths in the first section based on information indicating the operation state of the optical communication service; Based on the first polarization characteristic value common to the first section, a first polarization characteristic average value, which is an average value of the first polarization characteristic values, is calculated, and based on the first polarization characteristic value and the first polarization characteristic average value of a combined section obtained by combining adjacent first sections, a second polarization characteristic average value, which is an average value of the first polarization characteristic values in the combined section, is calculated. When there is no second section adjacent to the coupling section in the transmission direction of the signal light including any of the plurality of wavelengths, an estimation unit that estimates the limit value of the polarization characteristic value of the optical path as a constant multiple of the second polarization characteristic average value based on the Maxwell distribution in which the generation probability of the limit value is fixed and the second polarization characteristic average value; An optical transmission path characteristic estimation device having the above. **Claim 6** A collection unit that collects the speed of polarization fluctuation generated in the first section; A specifying unit that specifies the first section in which the amount of polarization fluctuation corresponding to the speed of the polarization fluctuation exceeds a threshold amount of fluctuation and a part of the plurality of wavelengths; The acquisition unit acquires the first polarization characteristic value and the second polarization characteristic value of a part of the plurality of wavelengths in the first section specified by the specifying unit; The calculation unit calculates the polarization characteristic average value based on the first polarization characteristic value and the second polarization characteristic value. The optical transmission path characteristic estimation device according to claim 2, characterized by the above. **Claim 7** The calculation unit determines whether the set of the first polarization characteristic values conforms to the cumulative distribution function of the Maxwell distribution based on a goodness-of-fit test; When the set does not conform to the cumulative distribution function, the acquisition unit acquires the first polarization characteristic values until the goodness-of-fit test is satisfied. The optical transmission path characteristic estimation device according to claim 3, characterized by the above. **Claim 8** Including a selection unit that selects a signal type of signal light using the plurality of wavelengths based on the limit value estimated by the estimation unit; The optical transmission path characteristic estimation device according to claim 3, characterized by the above. **Claim 9** In an optical transmission system including a plurality of nodes having an optical device with a CDC function and a wavelength-variable optical transceiver, Based on the instruction of the optical transmission path characteristic estimation device according to claim 1, the wavelength of the optical transceiver and the path of the optical device having the CDC function are set, and the second polarization characteristic value is acquired. An optical transmission system characterized by the above. **Claim 10** An optical transmission path characteristic estimation method in which a computer estimates the polarization characteristic value of an optical path in which a first section during service operation of an optical communication service using a plurality of wavelengths and a second section outside service operation are mixed, Based on information indicating the operation state of the optical communication service, the first polarization characteristic value of each of the plurality of wavelengths in the first section is acquired, and the second polarization characteristic value of each of the plurality of wavelengths in the second section is acquired. Based on the first polarization characteristic value and the second polarization characteristic value, calculating a wavelength-specific polarization characteristic value for each of the plurality of wavelengths of the optical path. An optical transmission path characteristic estimation method characterized by the above.

11. An optical transmission path characteristic estimation device for estimating a characteristic value that varies temporally according to the polarization characteristic of an optical transmission path including a plurality of nodes arranged from one end to the other end of an optical network, An acquisition unit that acquires a signal quality index of the signal light after propagating through the optical transmission path from a receiving node arranged at the other end of the optical network; A calculation unit that calculates a quality change amount for a certain period of the signal quality index; An estimation unit that estimates the characteristic value based on the quality change amount; An optical transmission path characteristic estimation device having the above.

12. The calculation unit calculates the quality change amount based on the average value of the signal quality index and the Maxwell distribution. The optical transmission path characteristic estimation device according to claim 11, characterized by the above.

13. When the acquisition unit detects a change in the operating state including an increase or decrease in the number of wavelengths in an optical communication service using a plurality of wavelengths provided by the optical network, the acquired signal quality index is discarded and the signal quality index is acquired again. The optical transmission path characteristic estimation device according to claim 11 or 12, characterized by the above.

14. When the acquisition unit detects a change in the operating state including an increase or decrease in the number of wavelengths in an optical communication service using a plurality of wavelengths provided by the optical network, the acquisition unit calculates a difference between the signal quality indexes before and after the change in the operating state, and corrects the acquired signal quality index based on the difference. The optical transmission path characteristic estimation device according to claim 11 or 12, characterized by the above.

15. The acquisition unit acquires a loss index representing the power loss of the signal light generated in a section from a second relay node arranged upstream of the first relay node to the first relay node from the first relay node arranged between the one end and the other end of the optical network, The calculation unit calculates a new signal quality index obtained by removing the signal quality change amount calculated based on the loss index for the certain period from the signal quality index, The estimation unit estimates the characteristic value based on the new signal quality index. The optical transmission path characteristic estimation device according to claim 11 or 12, characterized by the above.

16. The acquisition unit acquires a power index representing the input power of the signal light input to the receiving node from the receiving node. The calculation unit calculates a new signal quality index obtained by excluding the signal quality change amount calculated based on the power index during the fixed period from the signal quality index. The estimation unit estimates the characteristic value based on the new signal quality index. The optical transmission path characteristic estimation device according to claim 11 or 12, characterized in that.

17. An optical transmission path characteristic estimation method in which a computer estimates a characteristic value that varies temporally according to the polarization characteristic of an optical transmission path including a plurality of nodes arranged from one end to the other end of an optical network, acquiring a signal quality index of the signal light after propagating through the optical transmission path from a receiving node arranged at the other end of the optical network; calculating a quality change amount for a certain period of the signal quality index; estimating the characteristic value based on the quality change amount. An optical transmission path characteristic estimation method characterized by the above.

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