Transmission quality degradation determination device and transmission quality degradation determination method in optical transmission system

Abstract

To prevent an error or missing of a transmission quality degradation determination in an optical transmission system.SOLUTION: A transmission quality degradation determination device 10 in an optical transmission system includes: a degradation determination threshold value setting part 12; a degradation determination part 13 that determines the degradation in a transmission quality of a received optical signal; a time series data acquisition part 14 that acquires one or a plurality of types of time series data including the transmission quality data of the received optical signal; a time series data division part 15 that divides the time series data into a left window and a right window and calculates a variation index of the time series data of each of the left window, the right window, and all the windows; and a steady-state value change detection part 16 that instructs the degradation determination threshold setting part 12 to reset the degradation determination threshold value when it is determined that there is a change in a steady-state value of the acquired time-series data based on a relational expression for determining whether or not there is a change in the steady-state value of the acquired time-series data according to a mutual relationship between the variation indexes of the respective time-series data.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a transmission quality degradation determination device and a transmission quality degradation determination method in an optical transmission system. [Background technology]

[0002] In optical transmission systems, correction is generally performed at the optical receiver using forward error correction (FEC). The Q factor, calculated by conversion from the bit error rate before FEC (Pre-FEC BER), is one of the most important indicators (transmission quality indicators) for evaluating the quality of optical transmission. The Q factor decreases due to various types of degradation of the optical signal and the influence of noise on the optical signal. If the Q factor falls below the limit that can be corrected by FEC, it will affect communication services, such as packet loss.

[0003] FIG. 9 is a schematic diagram showing an example of transmission quality data (Q-factor). The horizontal axis of the graph represents time, and the vertical axis represents Q-factor (dB). Note that the Q-factor (dB) on the vertical axis is an average value over 15 minutes, and the range of the horizontal axis represents, for example, several hours, several days, or several tens of days. At times t1, t2, and t3, Q-factor data was measured that showed a significant drop from the steady-state value of the Q-factor. This phenomenon, in which the Q-factor suddenly drops temporarily and then recovers, is called a Q-drop. It is known that a Q-drop may be a sign of a malfunction. In this example, a malfunction occurs at time t4, and then the value falls below the correction limit (Q-limit).

[0004] Conventionally, technologies have been proposed to detect abnormal changes in the Q-factor (whether it has fallen below a threshold). For example, Non-Patent Documents 1 and 2 describe a degradation determination method that takes into account differences in the variation in transmission quality for each optical path. In this degradation determination method, the threshold (degradation determination threshold ThSF) for determining whether or not a Q-drop has occurred is determined based on the following equation (101):

[0005] ThSF= <q>-kσ … Equation (101)

[0006] where: <q>is the average of the Q values, σ is the standard deviation of the Q values, and k is a positive constant. For example, k=4 is used as the constant k. Furthermore, for example, Non-Patent Document 3 describes a method for detecting a Q-drop using the difference in the Q value between two times. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] C. Delezoide et al. ,"Pre-Emptive Detection and Localization of Failures Towards Marginless Operations of Optical Networks," 2018 20th International Conference on Transparent Optical Networks (ICTON), We.D2.3. [Non-patent document 2] Alba P. Vela et al. ,"Early Pre-FEC BER Degradation Detection to Meet Committed QoS," Optical Fiber Communication Conference, January 2017, DOI:10.1364 / OFC.2017.W4F.3 [Non-patent document 3] Kohei Watanabe and six others, "Proposal of a fault sign detection method using first-order differential series data of receiving end quality data of optical transmission systems," Proceedings of the IEICE Conference (CD-ROM), Japan, February 28, 2023, Volume: 2023, Issue: General Conference, Page: ROMBUNNO.B-6-55 Summary of the Invention [Problem to be solved by the invention]

[0008] In conventional technology, an abnormal change in the Q factor is detected when the steady-state value of the Q factor falls below a threshold. However, if the transmission conditions change, such as when the optical path route is changed, the steady-state value of the Q factor will also change. Therefore, in conventional technology, errors or omissions in determining degradation in transmission quality occur when the steady-state value of the Q factor changes due to a route change or other reason.

[0009] Therefore, an object of the present invention is to solve the above problems and prevent errors or omissions in determining transmission quality degradation in an optical transmission system. [Means for solving the problem]

[0010] a degradation determination unit that determines transmission quality degradation of an optical signal received at an optical receiving end based on the degradation determination threshold; a time-series data acquisition unit that acquires one or more types of time-series data including transmission quality data of the optical signal received at the optical receiving end; a time-series data division unit that selects, for each acquired data type, a predetermined region of the acquired time-series data using one time window, divides the time window into a first time window and a second time window at a predetermined time boundary, and calculates variation indices of each time-series data for the first time-series data arranged in the first time window, the second time-series data arranged in the second time window, and third time-series data arranged in the time window selected before the division; and a steady-state value change detection unit that, when it is determined that there is a change in the steady-state value of the acquired time-series data based on a predetermined relational expression that determines whether or not there is a change in the steady-state value of the acquired time-series data based on a mutual relationship between the variation indices of the respective time-series data, instructs the degradation determination threshold setting unit to reset the degradation determination threshold. [Effects of the Invention]

[0011] According to the present invention, it is possible to prevent errors or omissions in determining degradation in transmission quality in an optical transmission system. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a block diagram showing a configuration of a transmission quality degradation determination device according to an embodiment of the present invention; [Figure 2] 1 is a schematic configuration diagram of an optical transmission system including a transmission quality degradation determination device according to an embodiment of the present invention. [Figure 3] 1 shows time series data acquired by a transmission quality degradation determination device, where (a) is time series data of Q value and (b) is time series data of chromatic dispersion. [Figure 4] 10 is a flowchart showing the flow of a transmission quality degradation process performed by a transmission quality degradation determination device. [Figure 5] 10 is a flowchart showing the flow of steady-state value change determination processing performed by the transmission quality degradation determination device. [Figure 6] FIG. 10 is a conceptual diagram showing Example 1 in which a degradation determination threshold is reset. [Figure 7] FIG. 10 is a conceptual diagram showing Example 2 in which the degradation determination threshold value is reset. [Figure 8] 1 is a hardware configuration diagram illustrating an example of a computer that realizes the functions of a transmission quality degradation determination device according to an embodiment of the present invention. [Figure 9] FIG. 10 is a schematic diagram showing an example of transmission quality data (Q value). DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, the transmission quality degradation determination device according to this embodiment will be described in detail with reference to the drawings. [System configuration overview] The transmission quality degradation determination system 1 shown in FIG. 1 includes a transmission quality degradation determination device 10, an optical transmitter 20, and a management terminal 30 in an optical transmission system. As shown in FIG. 2, the optical transmission system includes a multiplexer / demultiplexer (optical cross connect) 102 and a transponder device 103 as network devices connected by an optical fiber 101. As an example, the transponder device 103 on the transmitting side in the optical transmission system is assumed to be an optical transmitter 20. Also, the transponder device 103 at the optical receiving end (optical receiving end) in the optical transmission system is assumed to function as a transmission quality degradation determination device 10. Here, the multiplexer / demultiplexer 102 on the transmitting side multiplexes optical signals from multiple transponder devices 103 (optical transmitters 20) on the transmitting side. The multiplexer / demultiplexer 102 on the receiving side selects an optical signal of a desired wavelength from a multiplexed optical signal in which optical signals of many different wavelengths are multiplexed, and outputs the selected optical signal to the transponder device 103 (transmission quality degradation determination device 10) at the optical receiving end. Note that the transmission quality degradation determination device 10 can be applied to optical transmission devices in general, into which an optical communication module can be inserted, in addition to transponder devices.

[0014] [Configuration of the transmission quality degradation detection device] As shown in FIG. 1, the transmission quality degradation determination device 10 includes an optical receiving terminal 11, a degradation determination threshold setting unit 12, a degradation determination unit 13, a time series data acquisition unit 14, a time series data division unit 15, and a steady-state value change detection unit 16.

[0015] The degradation determination threshold setting unit 12 sets the degradation determination threshold. In conventional technology, it was sufficient to set one degradation determination threshold, and the threshold obtained by one calculation remained a fixed value thereafter. On the other hand, when the degradation determination threshold setting unit 12 receives an instruction from the steady-state value change detection unit 16, it recalculates the degradation determination threshold to set a different value. The degradation determination threshold can be calculated, for example, based on statistical values ​​of measured transmission quality data. The degradation determination threshold can be set to a value calculated based on the temporal average value of the transmission quality data, or a value calculated based on a predetermined relational expression from the average value and standard deviation. The degradation determination threshold may be, for example, only a lower limit value (outside), or a set of an upper limit value (inside) and a lower limit value (outside).

[0016] The degradation determination unit 13 determines degradation of the transmission quality of the optical signal received at the optical receiving terminal 11 based on the degradation determination threshold. The degradation determination unit 13 determines degradation of the transmission quality based on the threshold set by the degradation determination threshold setting unit 12. The degradation determination unit 13 determines that the transmission quality has deteriorated when the measured transmission quality data falls below the degradation determination threshold (lower limit value), for example.

[0017] The time-series data acquiring unit 14 acquires one or more types of time-series data including transmission quality data (Q value) of the optical signal received at the optical receiving terminal 11. Other types of data that can be acquired besides the Q value include, for example, chromatic dispersion and polarization-mode dispersion (PMD). Chromatic dispersion is a physical phenomenon that occurs when the speed of each wavelength differs during transmission of an optical signal, causing distortion in the optical signal. Chromatic dispersion is monitored as the amount of chromatic dispersion compensation. Chromatic dispersion of optical fibers in a transmission path has small time fluctuations, making it suitable as time-series data to be used as an index. Polarization mode dispersion (PMD) is a physical phenomenon that occurs when the speed of light differs between two orthogonal axes during transmission, causing distortion in the optical signal. PMD is monitored as the amount of PM compensation.

[0018] The time series data acquisition unit 14 acquires time series data for the most recent predetermined period. The most recent period can be determined as a period in which the time series data includes a large number of measurements, and the length of the time series data may be, for example, eight hours.

[0019] The time series data division unit 15 selects a predetermined region of the acquired time series data for each acquired data type as one time window, and divides the time window into a first time window (hereinafter referred to as the left window) and a second time window (hereinafter referred to as the right window) using a predetermined time as a boundary. The time window selected before division will be referred to as the full window below. The time series data division unit 15 calculates a variability index for each of the time series data: the first time series data arranged in the left window, the second time series data arranged in the right window, and the third time series data (acquired time series data for a predetermined period) arranged in the full window.

[0020] Specifically, as shown schematically in FIG. 3( a), the time series data division unit 15 divides the entire window W into a left window WL and a right window WR. The length of the entire window W is, for example, 8 hours. At this time, the time series data division unit 15 divides the time series data of the Q value arranged in the entire window W into time series data arranged in the left window WL and time series data arranged in the right window WR. Furthermore, as shown schematically in FIG. 3( b), the time series data division unit 15 can also divide the time series data of the chromatic dispersion arranged in the entire window W into time series data arranged in the left window WL and time series data arranged in the right window WR. When dividing the entire window W, the time-series data dividing unit 15 sets the time regions of the left window WL and the right window WR to be continuous and not overlap each other. It is preferable that the left window WL and the right window WR have the same time width.

[0021] Variance, standard deviation, etc. can be used as the variation index used in the time-series data division unit 15. When the variation index is expressed as a cost function, which indicates a constant multiple of the variance, the time-series data division unit 15 calculates the variation index of each of the time-series data of the full window W, the left window WL, and the right window WR using the following formulas (1), (2), and (3).

[0022]

number

[0023] where x i denotes the i-th measurement value, mean(W) denotes the mean value of all measurements in all windows W, mean(WL) denotes the mean value of all measurements in the left window WL, and mean(WR) denotes the mean value of all measurements in the right window WR.

[0024] When the steady-state value change detection unit 16 determines based on a predetermined relational expression that there is a change in the steady-state value of the acquired time-series data, it instructs the deterioration determination threshold setting unit 12 to reset the deterioration determination threshold. The relational expression used by the steady-state value change detection unit 16 is a relational expression that determines whether or not there is a change in the steady-state value of the acquired time-series data based on the mutual relationship between the variability indexes of the time-series data of the full window, the left window, and the right window calculated by the time-series data division unit 15.

[0025] The steady-state value change detection unit 16 determines whether or not the difference value obtained by subtracting the variation index of the time-series data arranged in the left window and the variation index of the time-series data arranged in the right window from the variation index of the time-series data arranged in all windows for the acquired data type is equal to or greater than a predetermined steady-state value change threshold. The steady-state value change detection unit 16 determines a change in the steady-state value using, for example, a discrepancy value (difference value) shown in the following equation (4).

[0026]

number

[0027] Here, cost(W), cost(WL), and cost(WR) represent the variation indexes shown in the above-mentioned formulas (1) to (3). The steady-state value change detection unit 16 determines that there is a change if the discrepancy value shown in equation (4) is equal to or greater than the steady-state value change threshold. The steady-state value change threshold can be set to a desired upper limit. The steady-state value change threshold may also be determined by experiments or simulations using actually measured transmission quality data.

[0028] The steady-state value change detection unit 16 determines that there is a change in the steady-state value of the acquired time-series data when the discrepancy value (difference value) in any one of the acquired types of time-series data is equal to or greater than the steady-state value change threshold value. When the steady-state value change detection unit 16 determines that there is a change in the steady-state value of the acquired time-series data, it notifies the management terminal 30 that a steady-state value change has been detected.

[0029] [Operation of the transmission quality degradation determination device] Next, the operation of the transmission quality degradation determination device 10 will be described with reference to Fig. 4 and Fig. 5 (and Fig. 1 as appropriate). Fig. 4 is a flowchart showing the flow of the transmission quality degradation processing by the transmission quality degradation determination device 10. Fig. 5 is a flowchart showing the flow of the steady-state value change determination processing by the transmission quality degradation determination device 10.

[0030] First, as shown in FIG. 4, in the transmission quality degradation determination device 10, the degradation determination threshold setting unit 12 sets a degradation determination threshold (step S10). Then, the degradation determination unit 13 acquires a degradation determination threshold from the degradation determination threshold setting unit 12 (step S11). Furthermore, the degradation determination unit 13 acquires transmission quality data (Q value) of the optical signal received by the optical receiving end 11 (step S12). Then, the degradation determination unit 13 determines whether the transmission quality of the optical signal received by the optical receiving end 11 has deteriorated based on the degradation determination threshold (step S13). If the transmission quality has not deteriorated (step S13: No), the degradation determination unit 13 returns to step S11 and repeats the determination process. On the other hand, if the transmission quality has deteriorated (step S13: Yes), the degradation determination unit 13 notifies that the transmission quality has deteriorated (step S14).

[0031] Next, as shown in FIG. 5, in the transmission quality degradation determination device 10, the time series data acquisition unit 14 selects a predetermined data type related to time series data (step S21), and acquires time series data for the most recent predetermined period for the selected data type (step S22). Then, the time-series data dividing unit 15 obtains the time-series data of the data type from the time-series data obtaining unit 14, divides the time-series data into a left window WL and a right window WR, and calculates the variation index of the time-series data for each of the left window WL, the right window WR, and the whole window W (step S23).The steady-state value change detecting unit 16 then determines whether the steady-state value of the time-series data obtained for the data type has changed based on each variation index (step S24).

[0032] If the transmission quality degradation determination device 10 determines that the steady-state value of the acquired time-series data has not changed (step S24: No), and if there is another data type (step S25: Yes), it selects another data type (step S26) and returns to the process of step S22. On the other hand, if there is no other data type (step S25: No), the transmission quality degradation determination device 10 returns to the process of step S21, selects a predetermined data type again, and repeats the process. On the other hand, if it determines in step S24 that the steady-state value of the acquired time-series data has changed (step S24: Yes), the steady-state value change detection unit 16 instructs the degradation determination threshold setting unit 12 to reset the degradation determination threshold (step S27). Then, the steady-state value change detection unit 16 notifies the management terminal 30 that it has detected a steady-state value change (step S28).

[0033] [Example] Next, specific examples (examples) of the transmission quality degradation determination method according to this embodiment will be described with reference to Fig. 6 and Fig. 7. Fig. 6 is a conceptual diagram showing Example 1 in which the degradation determination threshold is reset, and Fig. 7 is a conceptual diagram showing Example 2 in which the degradation determination threshold is reset. Figs. 6 and 7 show the results of resetting the threshold (thick dashed line) for determining degradation at the timing when the transmission quality degradation determination device 10 determines that there is a change in the steady-state value of the Q factor.

[0034] In each graph, the thin solid line indicates the Q-value in arbitrary units (au). The thick solid line indicates the change-point detection score in arbitrary units (au) superimposed on the Q-value. The change-point detection score is the discrepancy value (difference value) shown in the above-mentioned formula (4). In each graph, the thin dashed line indicates the threshold for detecting change points (steady-state value change threshold). The thick dashed line indicates the threshold for determining deterioration (deterioration determination threshold). The deterioration determination threshold is calculated as the difference obtained by subtracting a predetermined constant from the "average." Here, the "average" is calculated using exponential smoothing.

[0035] The graph in Figure 6 shows that when the Q value (thin solid line) is roughly constant (steady state), there are two instances where the value changes (increases) due to route changes, etc. On the other hand, the graph in Figure 7 shows that when the Q value (thin solid line) is roughly constant (steady state), there is one instance where the value changes (decreases) due to route changes, etc. The two black circles in the graph in Figure 6 and the one black circle in the graph in Figure 7 indicate the points where a change in the steady-state value was detected (change points). The change points are the starting points for recalculating the "average." For reference, the three white circles in the graph in Figure 6 indicate the Q-drop. As shown in Figures 6 and 7, even immediately after the steady-state value (thin solid line) changes, the deterioration determination threshold (thick dashed line) does not become inappropriate, and it was found that the deterioration determination threshold was set correctly.

[0036] [Hardware configuration] The transmission quality degradation determination device 10 according to the embodiment is realized by, for example, a computer 900 configured as shown in Fig. 8. Fig. 8 is a hardware configuration diagram showing an example of the computer 900 that realizes the functions of the transmission quality degradation determination device 10 according to the embodiment. The computer 900 includes a CPU (Central Processing Unit) 901, a ROM (Read Only Memory) 902, a RAM (Random Access Memory) 903, an HDD (Hard Disk Drive) 904, an input / output I / F (Interface) 905, a communication I / F 906, and a media I / F 907.

[0037] The CPU 901 operates based on a program stored in the ROM 902 or the HDD 904. The ROM 902 stores a boot program executed by the CPU 901 when the computer 900 is started up, programs related to the hardware of the computer 900, and the like.

[0038] The CPU 901 controls an input device 910 such as a mouse or keyboard, and an output device 911 such as a display or printer, via an input / output I / F 905. The CPU 901 acquires data from the input device 910 via the input / output I / F 905, and outputs generated data to the output device 911. Note that a GPU (Graphics Processing Unit) or the like may be used as a processor together with the CPU 901.

[0039] The HDD 904 stores programs executed by the CPU 901 and data used by the programs, etc. The communication I / F 906 receives data from other devices via the communication network 920 and outputs the data to the CPU 901, and also transmits data generated by the CPU 901 to other devices via the communication network 920.

[0040] The media I / F 907 reads a program or data stored in the recording medium 912 and outputs it to the CPU 901 via the RAM 903. The CPU 901 loads a program related to a target process from the recording medium 912 onto the RAM 903 via the media I / F 907, and executes the loaded program. The recording medium 912 is an optical recording medium such as a DVD (Digital Versatile Disc) or a PD (Phase Change Rewritable Disc), a magneto-optical recording medium such as an MO (Magneto Optical Disk), a magnetic recording medium, or a semiconductor memory.

[0041] For example, when the computer 900 functions as the transmission quality degradation determination device 10 according to the embodiment, the CPU 901 executes a program (transmission quality degradation determination program) loaded onto the RAM 903 to realize the functions of the transmission quality degradation determination device 10. Furthermore, the HDD 904 stores data in the RAM 903. The CPU 901 reads and executes a program relating to a target process from the recording medium 912. In addition, the CPU 901 can also read a program relating to a target process from another device via the communication network 920.

[0042] [effect] As described above, the transmission quality degradation determination device 10 in the optical transmission system includes a degradation determination threshold setting unit 12 that sets a degradation determination threshold, a degradation determination unit 13 that determines transmission quality degradation for an optical signal received at the optical receiving terminal 11 based on the degradation determination threshold, a time series data acquisition unit 14 that acquires one or more types of time series data including transmission quality data, and a time series data acquisition unit 15 that selects a predetermined region of the acquired time series data with one time window W, divides the time window W into a first time window WL and a second time window WR at a predetermined time boundary, and calculates a first time series data arranged within the first time window WL. The time series data dividing unit 15 calculates a variation index for each of the time series data, including the first time series data, the second time series data placed in the second time window WR, and the third time series data placed in the time window W selected before the division; and a steady-state value change detection unit 16 that, when it is determined that there is a change in the steady-state value of the acquired time series data based on a predetermined relational expression that determines whether there is a change in the steady-state value of the acquired time series data based on the mutual relationship between the variation indexes of the time series data, instructs the degradation determination threshold setting unit 12 to reset the degradation determination threshold.

[0043] By doing this, in the transmission quality degradation determination device 10, the time series data acquisition unit 14 acquires time series data for a certain period of time in the most recent period, and the time series data division unit 15 divides the acquired time series data into left and right windows, calculates each variability index including the original time series data, and by using these, it is possible to determine whether or not there is a change in the steady-state value of the acquired time series data.As a result, the transmission quality degradation determination device 10 can detect slight degradation of transmission quality data that could not be detected by conventional technology when transmission conditions such as a route change change, and automatically reset the threshold.As a result, the transmission quality degradation determination device 10 can prevent errors or omissions in determining transmission quality degradation.

[0044] The transmission quality degradation determination device 10 in the optical transmission system is characterized in that the steady-state value change detection unit 16 determines whether or not the difference value obtained by subtracting the variation index of the first time series data and the variation index of the second time series data from the variation index of the third time series data for the acquired data type is equal to or greater than a predetermined steady-state value change threshold, and determines that there is a change in the steady-state value of the acquired time series data when the difference value is equal to or greater than the steady-state value change threshold for any one type of acquired time series data.

[0045] In this manner, the transmission quality degradation determination device 10 uses the difference value calculated by the steady-state value change detection unit 16 by subtracting the variation index for the left and right windows from the variation index for the full window to determine whether the steady-state value of the acquired time series data has changed. The difference value thus defined has the following characteristics: when a change point is exactly at the boundary between the left and right windows, the variation of each of the left and right windows becomes small; and, because the full window includes the change point, the variation of the full window becomes very large. Therefore, as the steady-state value change detection unit 16 sequentially repeats the operation of selecting a predetermined region of the acquired time series data using one time window (full window), this difference value suddenly increases only at the moment when the change point is exactly at the boundary between the left and right windows, and it is possible to reliably determine that the steady-state value of the acquired time series data has changed at this moment.

[0046] The transmission quality degradation determination device 10 in an optical transmission system is characterized in that when the steady-state value change detection unit 16 determines that there is a change in the steady-state value of the acquired time series data, it notifies the management terminal 30 that a steady-state value change has been detected.

[0047] By doing this, if there is a change in the steady-state value of the acquired time-series data, the transmission quality degradation determination device 10 notifies the management terminal 30 of this fact. This allows the operator of the management terminal 30 to confirm that the degradation determination threshold has been reset. Furthermore, the operator of the management terminal 30 can take preventive maintenance measures against failures in the optical transmission network in response to minor degradation in the transmission quality data.

[0048] The present invention is not limited to the above-described embodiments, and many modifications can be made by a person having ordinary skill in the art within the technical concept of the present invention. For example, when there are multiple types of data, the steady-state value change detector 16 may determine that there is a change in the steady-state values ​​of all the acquired types of time-series data when the difference values ​​are equal to or greater than the steady-state value change threshold value for all the acquired types of time-series data. In this case, it is possible to further prevent errors or omissions in determining transmission quality degradation. [Explanation of symbols]

[0049] 1. Transmission quality degradation judgment system 10 Transmission quality degradation determination device 11 Optical receiving end 12 Deterioration determination threshold setting unit 13 Deterioration determination section 14 Time series data acquisition section 15 Time series data division 16 Steady-state value change detection section 20 Optical transmitter 30 Management terminal W window (time window) WL Left window (first time window) WR Right Window (Second Time Window)< / q> < / q>

Claims

1. a deterioration determination threshold setting unit that sets a deterioration determination threshold; a degradation determination unit that determines a degradation in transmission quality of an optical signal received at an optical receiving end based on the degradation determination threshold; a time-series data acquisition unit that acquires one or more types of time-series data including transmission quality data of the optical signal received at the optical receiving end; a time series data division unit that selects a predetermined region of the acquired time series data for each acquired data type as one time window, divides the time window into a first time window and a second time window at a predetermined time as a boundary, and calculates a variability index for each of the first time series data arranged in the first time window, the second time series data arranged in the second time window, and the third time series data arranged in the time window selected before division; a steady-state value change detection unit that instructs the deterioration determination threshold setting unit to reset a deterioration determination threshold when it is determined that there is a change in the steady-state value of the acquired time-series data based on a predetermined relational expression that determines whether or not there is a change in the steady-state value of the acquired time-series data based on the mutual relationship between variation indexes of each time-series data; 1. A transmission quality degradation determination device in an optical transmission system, comprising:

2. The steady-state value change detection unit determining whether a difference value obtained by subtracting the variation index of the first time series data and the variation index of the second time series data from the variation index of the third time series data is equal to or greater than a predetermined steady-state value change threshold for the acquired data type; When the difference value is equal to or greater than a steady-state value change threshold in any one type of acquired time-series data, it is determined that there is a change in the steady-state value of the acquired time-series data.

2. The transmission quality degradation determination device in an optical transmission system according to claim 1.

3. When the steady-state value change detection unit determines that there is a change in the steady-state value of the acquired time-series data, it notifies a management terminal that a steady-state value change has been detected.

3. The transmission quality degradation determination device in an optical transmission system according to claim 1.

4. A transmission quality degradation determination method for a transmission quality degradation determination device in an optical transmission system, comprising: The transmission quality degradation determination device setting a degradation determination threshold; determining a degradation in transmission quality of an optical signal received at an optical receiving end based on the degradation determination threshold; acquiring one or more types of time-series data including transmission quality data of the optical signal received at the optical receiving end; a step of selecting a predetermined region of the acquired time series data as one time window for the acquired data type, dividing the time window into a first time window and a second time window at a predetermined time as a boundary, and calculating a variability index of each of the time series data for the first time series data arranged in the first time window, the second time series data arranged in the second time window, and the third time series data arranged in the time window selected before the division; a step of instructing resetting of the deterioration determination threshold when it is determined that there is a change in the steady-state value of the acquired time-series data based on a predetermined relational expression that determines whether or not there is a change in the steady-state value of the acquired time-series data based on the mutual relationship between the variation indexes of each time-series data; A method for determining transmission quality degradation, comprising:

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