COMMUNICATION DEVICE, COMMUNICATION CONTROL METHOD, PROGRAM, AND OPTICAL COMMUNICATION SYSTEM

Abstract

The present invention provides a communication device (1) that can easily determine a communication quality state. The communication device (1) comprises: an acquisition unit (2) that acquires a predetermined number or more of measurements of communication quality information in an optical communication channel; an estimation unit (3) that calculates an average value of the acquired measurements, generates a first cumulative distribution function of communication quality information based on the acquired measurements, and estimates a second cumulative distribution function of communication quality information on the basis of the average value and the first cumulative distribution function, the second cumulative distribution function being based on hypothetically-acquired measurements the number of which is greater than the number of the acquired measurements; and a determination unit (4) that determines, as a standard quality value, a value of communication quality information the cumulative probability of which becomes a predetermined value in the second cumulative distribution function.

Description

[Technical field]

[0001] The present disclosure relates to a communication device, a communication control method, a non-transitory computer-readable medium, and an optical communication system. [Background technology]

[0002] For example, as disclosed in Patent Document 1, optical communication systems that communicate via undersea cables generally perform powerful error correction processing, and therefore have much fewer signal errors than terrestrial communication systems. Thus, optical communication systems generally have a much smaller error rate in transmitted and received data, and are capable of providing end users with so-called error-free communication. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2011 / 037245 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the number of communication carriers that manage the communication infrastructure in optical communication systems has been diversifying. Therefore, it is expected that some communication carriers will want to secure the communication capacity of the communication infrastructure by setting the acceptable communication quality lower than the communication quality in error-free communication. In this way, the diversification of communication carriers that manage the communication infrastructure has made it necessary to consider not only the communication quality but also the communication capacity.

[0005] Here, in order to secure communication capacity in the communication infrastructure, it is necessary to change the communication settings. On the other hand, when changing the communication settings, it is necessary to consider not only the communication capacity but also the communication quality. Therefore, the communication carrier changes the communication settings after grasping the communication quality situation before and after the change of the communication settings. However, since the communication quality situation in the optical communication path is not always constant, a lot of verification time is required to grasp the communication quality situation. Therefore, there is a possibility that the communication carrier cannot easily grasp the communication quality situation in the optical communication path.

[0006] One of the objectives of the present disclosure has been made to solve the above-mentioned problem, and is to provide a communication device, a communication control method, a non-transitory computer-readable medium, and an optical communication system that make it possible to easily grasp the communication quality status. [Means for solving the problem]

[0007] A communication device according to the present disclosure includes: an acquisition means for acquiring a predetermined number or more of measured values ​​of communication quality information in an optical communication path; an estimation means for calculating an average value of the acquired measurement values, generating a first cumulative distribution function of the communication quality information based on the acquired measurement values, and estimating a second cumulative distribution function of the communication quality information based on the acquired measurement values ​​when more measurement values ​​than the number of acquired measurement values ​​are acquired, based on the average value and the first cumulative distribution function; The communication quality information determining means determines, as a reference quality value, a value of the communication quality information at which a cumulative probability becomes a predetermined value in the second cumulative distribution function.

[0008] The communication control method according to the present disclosure includes: Acquire a predetermined number or more of measured values ​​of communication quality information in the optical communication path; calculating an average value of the acquired measurement values, generating a first cumulative distribution function of the communication quality information based on the acquired measurement values, and estimating a second cumulative distribution function of the communication quality information based on a measurement value when a number of measurement values ​​acquired is greater than the number of acquired measurement values, based on the average value and the first cumulative distribution function; In the second cumulative distribution function, a value of the communication quality information at which the cumulative probability becomes a predetermined value is determined as a reference quality value.

[0009] The non-transitory computer readable medium according to the present disclosure comprises: Acquire a predetermined number or more of measured values ​​of communication quality information in the optical communication path; calculating an average value of the acquired measurement values, generating a first cumulative distribution function of the communication quality information based on the acquired measurement values, and estimating a second cumulative distribution function of the communication quality information based on a measurement value when a number of measurement values ​​acquired is greater than the number of acquired measurement values, based on the average value and the first cumulative distribution function; The non-transitory computer-readable medium stores a program for causing a computer to execute a process of determining, as a reference quality value, a value of the communication quality information at which a cumulative probability becomes a predetermined value in the second cumulative distribution function.

[0010] The optical communication system according to the present disclosure comprises: a first communication device and a second communication device connected to the first communication device via an optical communication path; The first communication device is measuring communication quality information in the optical communication path a predetermined number of times or more to obtain a predetermined number of measurement values ​​or more; The second communication device is calculating an average value of the acquired measurement values, generating a first cumulative distribution function of the communication quality information based on the acquired measurement values, and estimating a second cumulative distribution function of the communication quality information based on a measurement value when a number of measurement values ​​acquired is greater than the number of acquired measurement values, based on the average value and the first cumulative distribution function; In the second cumulative distribution function, a value of the communication quality information at which the cumulative probability becomes a predetermined value is determined as a reference quality value. Effect of the Invention

[0011] According to the present disclosure, it is possible to provide a communication device, a communication control method, a non-transitory computer-readable medium, and an optical communication system that are capable of easily grasping the communication quality status. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram showing a configuration example of a communication device according to a first embodiment; [Diagram 2] 5 is a flowchart illustrating an example of the operation of the communication device according to the first embodiment. [Diagram 3] FIG. 11 is a diagram illustrating a configuration example of an optical communication system according to a second embodiment. [Figure 4] FIG. 11 illustrates an overview of the operation of the optical transmission device according to the second embodiment. [Diagram 5] FIG. 11 illustrates an outline of an operation of the optical transmission device according to the second embodiment. [Figure 6] FIG. 11 illustrates an outline of an operation of the optical transmission device according to the second embodiment. [Figure 7] 11 is a flowchart illustrating an example of an operation of the optical transmission device according to the second embodiment. [Figure 8] 11 is a flowchart illustrating an example of an operation of the optical transmission device according to the second embodiment. [Figure 9] 11 is a flowchart illustrating an example of an operation of the optical transmission device according to the second embodiment. [Figure 10] FIG. 11 is a diagram illustrating a configuration example of an optical communication system according to a third embodiment. [Figure 11] FIG. 2 is a diagram illustrating an example of a hardware configuration of a communication device or the like. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Note that the following description and drawings are omitted and simplified as appropriate for clarity of explanation. In addition, in each of the following drawings, the same elements are given the same reference numerals, and duplicate explanations are omitted as necessary.

[0014] (Considerations leading to the embodiment) First, before describing the embodiment, the considerations that led to the embodiment will be described. Internet traffic via long-distance optical communication cables has been increasing rapidly. Therefore, various technologies have been developed to process Internet traffic. Examples include EDFA (Erbium Doped Fiber Amplifier), WDM (Wavelength Division Multiplexing), QAM (Quadrature Amplitude Modulation), FEC (Forward Error Correction), DSP (Digital Signal Processor), and low-loss optical fiber. Due to the development of such various technologies, the communication capacity of optical communication systems has become large along with the increase in Internet traffic.

[0015] Moreover, in order to provide communication services to many users, optical communication networks are becoming larger in scale and more sophisticated in order to efficiently multiplex a large amount of data. In optical communication, it is also an issue to efficiently utilize the frequency resources of optical communication signals in optical fibers. Therefore, as an optical communication method for the future, a communication method that divides the optical communication signal frequency resources into short periods of time is being considered. As such a communication method, a communication method called an optical path switch or an optical packet switch can be mentioned. Furthermore, extremely high reliability and communication signal quality are required for the backbone communication network. Therefore, the current backbone communication network has achieved an extremely high operation rate and an extremely low communication signal error rate.

[0016] As described above, in recent years, the number of communication carriers that manage optical communication paths in optical communication systems has been diversifying. As the number of communication carriers has increased, the opportunities for changing communication settings in optical communication paths have also increased. When the communication settings of an optical communication path are changed, the impact of the change in communication settings is large, so the communication carriers change the communication settings after careful verification.

[0017] However, since data from many users is transmitted and received via commercial networks, telecommunications carriers conduct verification during commercial network maintenance times, which are generally short. Since the communication quality of optical communication signals in optical fibers is generally not constant but fluctuates, telecommunications carriers identify the quality of optical communication signals by taking measurements over a sufficiently long period of time. Thus, in optical communication networks, control of optical communication signals with short time granularity is required from the viewpoint of frequency resource efficiency. Therefore, the present disclosure realizes a configuration in which telecommunications carriers grasp the communication quality of optical communication paths using measurement values ​​measured in a time shorter than the time required to identify the communication quality.

[0018] (Embodiment 1) A configuration example of a communication device 1 according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a block diagram showing a configuration example of a communication device according to the first embodiment. The communication device 1 is a communication device constituting an optical communication system. The communication device 1 may be, for example, an optical transmission device or a network monitoring device that monitors and controls the optical communication system. The communication device 1 includes an acquisition unit 2, an estimation unit 3, and a determination unit 4.

[0019] The acquiring unit 2 acquires a predetermined number or more of measurement values ​​measured for communication quality information in the optical communication path. The acquiring unit 2 may acquire the predetermined number or more of measurement values ​​by performing measurement of communication quality information in the optical communication path for a predetermined measurement time a predetermined number or more times. Alternatively, the acquiring unit 2 may acquire the predetermined number or more of measurement values ​​by receiving from another communication device (not shown) the predetermined number or more of measurement values ​​that the other communication device has acquired by performing measurement of communication quality information in the optical communication path for a predetermined measurement time a predetermined number or more times. The predetermined measurement time may be set to any time, for example, 1 second or more. Also, the predetermined number of times may be set to any number, for example, 10 times or more.

[0020] The communication quality information may be a bit error rate (BER) indicating an error rate before error correction, or a Q value indicating an optical quality value. The BER may be a BER based on bits included in a data unit generated from an optical communication signal transmitted through an optical communication path, or a BER based on a recovery rate of a data unit generated from an optical communication signal.

[0021] The estimation unit 3 calculates the average value of the measurement values ​​acquired by the acquisition unit 2. The estimation unit 3 also generates a first cumulative distribution function indicating a cumulative distribution function of the communication quality information based on the measurement values ​​acquired by the acquisition unit 2. The estimation unit 3 generates a cumulative distribution indicating the relationship between the value of the communication quality information and a cumulative density, using the measurement values ​​acquired by the acquisition unit 2. The estimation unit 3 generates the first cumulative distribution function by obtaining an approximation curve for the generated cumulative distribution, for example, by using the least squares method or the like.

[0022] The estimation unit 3 estimates a second cumulative distribution function indicating a cumulative distribution function of communication quality information based on the measurement values ​​when more measurement values ​​than the number of acquired measurement values ​​are acquired, based on the calculated average value and the generated first cumulative distribution function. In other words, the estimation unit 3 estimates a cumulative distribution function of communication quality information based on the average value and the first cumulative distribution function, which is generated based on the measurement values ​​when the measurement values ​​are acquired in a total measurement time longer than the total measurement time required by the acquisition unit 2 to acquire the measurement values.

[0023] The determination unit 4 determines the value of the communication quality information at which the cumulative probability becomes a predetermined value in the second cumulative distribution function as the reference quality value. The reference quality value is a quality value that serves as a standard for evaluating the communication quality status of the optical communication path, and is a quality value used for evaluating whether or not the required communication quality value required by the communication carrier is satisfied. The required quality value is a threshold value of the communication quality information at which communication cannot be established in the optical communication path.

[0024] Next, an operation example of the communication device 1 according to the first embodiment will be described with reference to Fig. 2. Fig. 2 is a flowchart showing an operation example of the communication device according to the first embodiment. The acquiring unit 2 acquires a predetermined number or more of measured values ​​of communication quality information in an optical communication path (step S1). The acquiring unit 2 may acquire a predetermined number or more of measurement values ​​of communication quality information in the optical communication path by performing measurement for a predetermined measurement time a predetermined number or more times. Alternatively, the acquiring unit 2 may acquire a predetermined number or more of measurement values ​​by receiving from another communication device (not shown) a predetermined number or more of measurement values ​​that the other communication device has acquired by performing measurement for a predetermined measurement time a predetermined number or more times of communication quality information in the optical communication path.

[0025] The estimation unit 3 calculates the average value of a predetermined number or more of the measured values ​​acquired by the acquisition unit 2 (step S2). The estimation unit 3 generates a first cumulative distribution function indicating a cumulative distribution function of the communication quality information based on the measurement value acquired by the acquisition unit 2 (step S3). The estimation unit 3 generates a cumulative distribution that indicates a relationship between the value of the communication quality information and the cumulative density, using the measurement value acquired by the acquisition unit 2. The estimation unit 3 generates a first cumulative distribution function by obtaining an approximation curve for the generated cumulative distribution, for example, by using the least squares method or the like.

[0026] The estimation unit 3 estimates a second cumulative distribution function indicating a cumulative distribution function of communication quality information based on the measurement values ​​when more measurement values ​​than the number of acquired measurement values ​​are acquired, based on the calculated average value and the generated first cumulative distribution function (step S4). The determination unit 4 determines, as a reference quality value, a value of the communication quality information at which the cumulative probability becomes a predetermined value in the second cumulative distribution function (step S5).

[0027] The estimation unit 3 calculates an average value of the acquired measurement values ​​based on a predetermined number or more of measurement values ​​measured for the communication quality information in the optical communication path, and generates a first cumulative distribution function. The estimation unit 3 estimates a second cumulative distribution function of the communication quality information in a case where more measurement values ​​than the number of acquired measurement values ​​are acquired based on the calculated average value and the generated first cumulative distribution function. The determination unit 4 determines a reference quality value indicating a quality value with a cumulative probability of a predetermined value in the second cumulative distribution function. In this way, the communication device 1 can determine a reference quality value in a case where more measurement values ​​than the number of actually measured measurement values ​​are acquired based on the measurement values ​​of the communication quality information. Therefore, by using the communication device 1, the communication carrier can determine a reference quality value in a case where a large number of measurement values ​​are acquired without acquiring a large number of measurement values. In other words, by using the communication device 1, the communication carrier can determine a reference quality value of a measurement value that is predicted to be acquired in a total measurement time longer than the total measurement time actually measured, based on the measurement values ​​acquired in a short total measurement time. Therefore, according to the communication device 1 according to the first embodiment, the communication carrier can easily grasp the communication quality situation.

[0028] (Embodiment 2) Next, a description will be given of embodiment 2. Embodiment 2 is an embodiment in which embodiment 1 is made more detailed. <Example of optical communication system configuration> A configuration example of an optical communication system 100 according to the second embodiment will be described with reference to Fig. 3. Fig. 3 is a diagram showing a configuration example of an optical communication system according to the second embodiment. The optical communication system 100 includes terminal devices 10 and 40, and optical transmission devices 20 and 30.

[0029] The terminal devices 10 and 40 are, for example, communication devices installed on land. The terminal device 10 may be, for example, an end-user terminal managed by an end user, or may be a relay device or the like installed between the end-user terminal and the optical transmission device 20. The terminal device 40 may be, for example, an end-user terminal managed by an end user, or may be a relay device or the like installed between the end-user terminal and the optical transmission device 30. In the following description, the terminal devices 10 and 40 will be described as end-user terminals.

[0030] The terminal device 10 is connected to the optical transmission device 20 via a communication path P1 and communicates with the optical transmission device 20 via the communication path P1. The terminal device 40 is connected to the optical transmission device 30 via a communication path P3 and communicates with the optical transmission device 30 via the communication path P3. The communication paths P1 and P3 are, for example, access lines.

[0031] The optical transmission devices 20 and 30 are connected to each other via an optical communication path P2 and communicate with each other via the optical communication path P2. The optical communication path P2 is, for example, configured by an optical cable such as an optical fiber that is laid on the ocean floor. The optical transmission devices 20 and 30 convert optical communication signals transmitted and received via the optical communication path P2 into electrical signals transmitted and received via the communication paths P1 and P3, respectively. The optical transmission devices 20 and 30 convert electrical signals transmitted and received via the communication paths P1 and P3, respectively, into optical communication signals transmitted and received via the optical communication path P2.

[0032] The optical transmission devices 20 and 30 are compatible with WDM (Wavelength Division Multiplexing) and transmit data transmitted and received over the optical communication path P2 to the opposing optical transmission device via multiple communication channels configured in multiple wavelength bands. Each communication channel may be referred to as an optical spectrum.

[0033] The optical transmission device 20 transmits data transmitted from the terminal device 10 to the terminal device 40 via the optical communication path P2 and the optical transmission device 30. The optical transmission device 30 transmits data transmitted from the terminal device 40 to the terminal device 10 via the optical communication path P2 and the optical transmission device 20.

[0034] <Example of optical transmission device configuration> Next, a description will be given of configuration examples of the optical transmission devices 20 and 30. First, before describing the configuration example of the optical transmission device 20, a configuration example of the optical transmission device 30 will be described, and then the configuration example of the optical transmission device 30 will be described.

[0035] The optical transmission device 30 includes a communication unit 31 and a measurement unit 32 . The communication unit 31 communicates with the terminal device 40 and with the optical transmission device 20. The communication unit 31 receives an optical communication signal from the optical transmission device 20 via the optical communication path P2, and restores a data unit based on a bit string included in the optical communication signal. The communication unit 31 extracts a communication frame from the data unit and transmits it to the terminal device 40 via the communication path P3. The communication unit 31 receives a communication frame from the terminal device 40 via the communication path P3. The communication unit 31 stores the received communication frame in a data unit, and converts the data unit into an optical communication signal. The communication unit 31 transmits the optical communication signal to the optical transmission device 20 via the optical communication path P2.

[0036] The communication unit 31 receives an acquisition request from the optical transmission device 20 and notifies (transmits) the measurement unit 32 of the receipt of the acquisition request. The acquisition request is a request from the optical transmission device 20, and is a message from the optical transmission device 20 to the measurement unit 32 requesting that the measurement unit 32 measure communication quality information in the optical communication path P2. The communication unit 31 transmits the multiple measurement values ​​acquired by the measurement unit 32 to the optical transmission device 20 via the optical communication path P2.

[0037] When an acquisition request is received, the measurement unit 32 measures the communication quality information in the optical communication path P2 and acquires a predetermined number of measurement values ​​or more. Every time an acquisition request is received from the optical transmission device 20, the measurement unit 32 performs measurement for a predetermined measurement time a predetermined number of times or more and acquires a predetermined number of measurement values ​​or more. The measurement unit 32 transmits the acquired measurement values ​​or more to the optical transmission device 20 via the communication unit 31.

[0038] The measurement unit 32 measures communication quality information in the optical communication path for a predetermined measurement time, and obtains one measurement value. The predetermined measurement time is, for example, a measurement time set to an arbitrary time of 1 second or more. The measurement unit 32 performs measurement for the predetermined measurement time a predetermined number of times or more until a predetermined number of measurement values ​​or more are obtained. The predetermined number of times is, for example, a number set to an arbitrary number of times of 10 or more. The higher the predetermined number of times, the higher the accuracy of the results, so for example, 500 times or more is preferable, but the higher the number of times, the longer the total measurement time becomes, so the number is determined taking into consideration the accuracy and the total measurement time.

[0039] The communication quality information may be a BER indicating an error rate before error correction, or a Q value indicating an optical quality value. The BER may be a BER based on bits included in a data unit generated from an optical communication signal transmitted through an optical communication path, or a BER based on a recovery rate of a data unit generated from an optical communication signal.

[0040] When the communication quality information is a BER based on bits included in a data unit generated from an optical communication signal transmitted through an optical communication path, the measurement unit 32 measures a bit string included in the data unit restored by the communication unit 31 multiple times. The measurement unit 32 may calculate a BER of the measured bit string and obtain the calculated BER as a measurement value.

[0041] When the communication quality information is a BER based on a recovery rate of a data unit generated from an optical communication signal, the measurement unit 32 measures the number of attempts made by the communication unit 31 to recover the data unit and the number of successes or failures in recovering the data unit by the communication unit 31. The measurement unit 32 calculates the BER based on the number of attempts and the number of successes or failures, and obtains the calculated BER as a measurement value.

[0042] When the communication quality information is a Q value, the Q value can be calculated by logarithmizing the above-mentioned BER, so the measurement unit 32 calculates the BER and then logarithmizes the calculated BER to calculate the Q value. The measurement unit 32 may measure the probability distribution of each of the signal values ​​(0 and 1) of the optical communication signal transmitted and received via the optical communication path P2, and the demodulated signal level. The measurement unit 32 may calculate the Q value based on the variance of the probability distribution of each of the optical communication signal values ​​1 and 0, and the difference value of the demodulated signal level, and obtain the calculated Q value as a measurement value.

[0043] Next, the optical transmission device 20 will be described. The optical transmission device 20 corresponds to the communication device 1 according to the first embodiment. The optical transmission device 20 includes a communication unit 21, an acquisition unit 22, a cumulative distribution estimation unit 23, a communication quality determination unit 24, a control unit 25, and a storage unit 26.

[0044] The communication unit 21 communicates with the terminal device 10 and with the optical transmission device 30. The communication unit 21 receives an optical communication signal from the optical transmission device 30 via the optical communication path P2, and restores a data unit based on a bit string included in the optical communication signal. The communication unit 21 extracts a communication frame from the data unit and transmits it to the terminal device 10 via the communication path P1. The communication unit 21 receives a communication frame from the terminal device 10 via the communication path P1. The communication unit 21 stores the received communication frame in a data unit and converts the data unit into an optical communication signal. The communication unit 21 transmits the optical communication signal to the optical transmission device 30 via the optical communication path P2.

[0045] The communication unit 21 receives a quality status confirmation request and a parameter adjustment request. The quality status confirmation request is, for example, a request from a communication carrier managing the optical communication path P2 to confirm the current communication quality status in the optical communication path P2. The parameter adjustment request is, for example, a request from a communication carrier managing the optical communication path P2 to adjust parameters related to communication settings in the optical communication path P2 based on the communication quality status in the optical communication path P2. The communication unit 21 receives the quality status confirmation request and the parameter adjustment request from, for example, the communication carrier via a network monitoring device (not shown). The communication unit 21 transmits the quality status confirmation request and the parameter adjustment request to the cumulative distribution estimation unit 23 and the communication quality determination unit 24. The communication unit 21 also transmits the parameter adjustment request to the control unit 25.

[0046] When the communication unit 21 receives a quality status confirmation request, it transmits an acquisition request to the communication unit 31. When the communication unit 21 receives a parameter adjustment request, it transmits an acquisition request to the communication unit 31. Furthermore, when the communication unit 21 receives a parameter adjustment request, the control unit 25, which will be described later, changes parameters in consideration of the communication quality status in the optical communication path P2. The communication unit 21 transmits an acquisition request to the communication unit 31 every time the control unit 25 changes parameters.

[0047] After transmitting the acquisition request, the communication unit 21 receives the predetermined number or more of measurement values ​​acquired by the measurement unit 32 from the communication unit 31 via the optical communication path P2. The communication unit 21 outputs the received predetermined number or more of measurement values ​​to the acquisition unit 22.

[0048] The acquiring unit 22 corresponds to the acquiring unit 2 in the first embodiment. The acquiring unit 22 acquires a predetermined number or more of measurement values ​​measured on the communication quality information in the optical communication path P2. The acquiring unit 22 acquires the predetermined number or more of measurement values ​​acquired by the measuring unit 32 via the communication unit 21.

[0049] The cumulative distribution estimation unit 23 corresponds to the estimation unit 3 in the first embodiment. When a predetermined number or more of measurement values ​​are acquired in response to a quality status confirmation request, the cumulative distribution estimation unit 23 calculates an average value of the acquired measurement values ​​and generates a first cumulative distribution function indicating a cumulative distribution function of communication quality information based on the acquired measurement values. The cumulative distribution estimation unit 23 estimates a second cumulative distribution function indicating a cumulative distribution function of communication quality information based on the measurement values ​​when more measurement values ​​than the number of acquired measurement values ​​are acquired, based on the calculated average value and the generated first cumulative distribution function. The first cumulative distribution function is known because it is a function based on the acquired measurement values, but the second cumulative distribution function is unknown because it is a cumulative distribution function when it is assumed that more measurement values ​​than the number of acquired measurement values ​​are acquired. Therefore, the cumulative distribution estimation unit 23 estimates an unknown second cumulative distribution function based on the calculated average value and the known first cumulative distribution function.

[0050] Specifically, when a predetermined number or more of measurement values ​​are acquired in response to a quality status check request, the cumulative distribution estimation unit 23 calculates the average value of the acquired measurement values. When a predetermined number or more of measurement values ​​are acquired in response to a quality status check request, the cumulative distribution estimation unit 23 generates a first cumulative distribution function indicating a cumulative distribution function of communication quality information based on the predetermined number or more of acquired measurement values. Based on the acquired measurement values, the cumulative distribution estimation unit 23 generates a cumulative distribution with the horizontal axis representing the value of communication quality information and the vertical axis representing cumulative probability. The cumulative distribution estimation unit 23 generates the first cumulative distribution function by obtaining an approximation curve for the points plotted as the generated cumulative distribution using, for example, the least squares method or the like.

[0051] The cumulative distribution estimation unit 23 calculates the slope of the first cumulative distribution function in a region where the cumulative probability changes sharply. It is predicted that the histogram of the values ​​of the communication quality information regarding the optical communication signal transmitted through the optical communication path P2 follows a Gaussian distribution. Therefore, in the first cumulative distribution function, for example, a region where the cumulative probability is 0.1 to 0.9 is a region where the cumulative probability changes sharply. Therefore, the cumulative distribution estimation unit 23 calculates the slope of the first cumulative distribution function in a region where the cumulative probability changes sharply, such as a region where the cumulative probability is 0.1 to 0.9.

[0052] The cumulative distribution estimation unit 23 may calculate the slope at a point where the cumulative probability is 0.5 in the first cumulative distribution function as the slope in the region where the cumulative probability changes sharply. Alternatively, the cumulative distribution estimation unit 23 may select a plurality of points where the cumulative probability is within a predetermined range, such as 0.1 to 0.9, from among the points that satisfy the first cumulative distribution function, and calculate the slope in the region where the cumulative probability changes sharply based on the slope at the selected points. The cumulative distribution estimation unit 23 may calculate the slope at the selected points, and calculate the average value, median value, minimum value, or maximum value of the calculated slopes, and calculate the calculated value as the slope in the region where the cumulative probability changes sharply. The cumulative distribution estimation unit 23 stores the calculated average value and slope in the storage unit 26.

[0053] The cumulative distribution estimation unit 23 estimates the second cumulative distribution function by approximating the second cumulative distribution function in a region where the cumulative probability changes sharply to a straight line based on the average value and the slope. The cumulative distribution estimation unit 23 determines a straight line that passes through a point where the calculated average value is the value of the communication quality information at the point where the cumulative probability is 0.5, and has the calculated slope. The cumulative distribution estimation unit 23 estimates the second cumulative distribution function by approximating the second cumulative distribution function in a region where the cumulative probability changes sharply to the determined straight line.

[0054] When the cumulative distribution estimation unit 23 receives a parameter adjustment request from the communication unit 21 and the control unit 25 has not changed the parameters, the cumulative distribution estimation unit 23 performs the same processing as for the quality status confirmation request. Moreover, when the cumulative distribution estimation unit 23 receives a parameter adjustment request from the communication unit 21 and the control unit 25 has changed the parameters, the cumulative distribution estimation unit 23 performs processing according to the changed parameters.

[0055] When the control unit 25 changes the variance dissimilarity parameter, which is a parameter whose variance depends on the value of the communication quality information, the cumulative distribution estimation unit 23 performs the same process as the quality status confirmation request. Specifically, when the variance dissimilarity parameter is changed, the cumulative distribution estimation unit 23 generates a first cumulative distribution function based on the measurement value acquired after the variance dissimilarity parameter is changed. The cumulative distribution estimation unit 23 calculates the slope of the first cumulative distribution function based on the measurement value acquired after the variance dissimilarity parameter is changed in a region where the cumulative probability is steep. The cumulative distribution estimation unit 23 calculates the average value of the measurement value acquired after the variance dissimilarity parameter is changed. The cumulative distribution estimation unit 23 determines a straight line that passes through a point where the communication quality information value at which the cumulative probability is 0.5 is the calculated average value and has the calculated slope as the slope. The cumulative distribution estimation unit 23 approximates the determined straight line to the second cumulative distribution function in a region where the cumulative probability changes steeply among the second cumulative distribution functions. The cumulative distribution estimation unit 23 stores the calculated average value and slope in the storage unit 26 together with the name of the parameter changed by the control unit 25 and the parameter values ​​before and after the change.

[0056] The variance dissimilarity parameter may include, for example, the modulation method in the optical communication path P2 and the guard band of the communication channel in the optical communication path P2. For example, it is assumed that the range of the communication quality information value in which the cumulative probability in the cumulative distribution function is from 0 to 100 when the modulation method is QPSK (Quadra phase-shift keying) is narrowed even in the case of 16QAM (Quadrature amplitude modulation). In this way, when the order of the modulation method is changed, it is assumed that the variance of the communication quality information value is different. In addition, when the guard band of each communication channel in the optical communication path P2 is changed so as to be wider, it is assumed that the range of the communication quality information value in which the cumulative density of the cumulative density function is from 0 to 100 also becomes narrower, similar to the modulation method. Therefore, when the variance dissimilarity parameter is changed, the cumulative distribution estimation unit 23 calculates the average value of the measurement values ​​acquired after the variance dissimilarity parameter is changed. The cumulative distribution estimation unit 23 calculates the slope in a region where the change in the cumulative probability of the first cumulative distribution function based on the measurement values ​​acquired after the variance dissimilarity parameter is changed is steep.

[0057] The order of the modulation scheme may be referred to as the multi-value degree of the modulation scheme. Also, the fact that the variance of the communication quality information value is not similar before and after the parameter change means that the cumulative distribution function is not similar before and after the parameter change, so the variance dissimilarity parameter may be referred to as the parameter with the cumulative distribution function being not similar.

[0058] On the other hand, when the control unit 25 changes a variance-like parameter in which the variance of the communication quality information value does not depend on the parameter value, the cumulative distribution estimation unit 23 calculates the difference between the average value before the parameter change and the reference quality value determined before the parameter change as a margin value. The cumulative distribution estimation unit 23 calculates the average value of the measurement values ​​acquired after the variance-like parameter is changed. The reference quality value is a value of communication quality information at which the cumulative probability becomes a predetermined value in the second cumulative distribution function, and is a value determined by the communication quality determination unit 24 described later.

[0059] When the variance-like parameter is changed, the slope of the straight line approximating the second cumulative distribution function is the same before and after the change of the variance-like parameter. Therefore, the cumulative distribution estimation unit 23 does not determine a straight line approximating the second cumulative distribution function after the parameter change, but calculates the shift amount of the straight line before and after the change of the variance-like parameter as a margin value. The cumulative distribution estimation unit 23 stores the calculated average value and margin value in the storage unit 26 together with the parameter name changed by the control unit 25 and the values ​​before and after the change. Note that the margin value is not changed even when the variance-like parameter is changed, so the cumulative distribution estimation unit 23 may calculate the margin value only once when the variance-like parameter is changed.

[0060] The variance-like parameter is, for example, the optical transmission output in the optical communication path P2, the number of communication channels in the optical communication path P2, etc. Note that the fact that the variance is similar before and after a parameter change means that the cumulative distribution functions are similar before and after the parameter change, so the variance-like parameter may be referred to as a parameter whose cumulative distribution function is similar.

[0061] The communication quality determination unit 24 corresponds to the determination unit 4 in the first embodiment. When a predetermined number or more of measurement values ​​are acquired in response to a quality status confirmation request, the communication quality determination unit 24 determines, as a reference quality value, a value of communication quality information at which the cumulative probability is a predetermined value, using a straight line approximating the second cumulative distribution function. The communication quality determination unit 24 assumes that the reference quality value exists on a straight line based on the calculated average value and slope, and determines, as a reference quality value, a value of communication quality information at a point on the straight line at which the cumulative probability is a predetermined value. The communication quality determination unit 24 stores the determined reference quality value in the storage unit 26 in association with the average value and slope used to calculate the reference quality value.

[0062] When the communication quality determination unit 24 receives a parameter adjustment request from the communication unit 21 and the control unit 25 has not changed the parameters, the communication quality determination unit 24 performs the same process as for a quality status confirmation request. Moreover, when the communication quality determination unit 24 receives a parameter adjustment request from the communication unit 21 and the control unit 25 has changed the parameters, the communication quality determination unit 24 performs a process according to the changed parameters.

[0063] When the control unit 25 changes the variance dissimilarity parameter, the communication quality determination unit 24 performs the same process as the quality status confirmation request. Specifically, the communication quality determination unit 24 determines, as the reference quality value, the value of the communication quality information at which the cumulative probability is a predetermined value, using a straight line that is approximated to the second cumulative distribution function. The communication quality determination unit 24 determines, as the reference quality value, the value of the communication quality information at a point on the straight line based on the calculated average value and slope, at which the cumulative probability is a predetermined value. The communication quality determination unit 24 stores the reference quality value after the parameter change in the storage unit 26 in association with the name of the parameter changed by the control unit 25 and the values ​​before and after the change.

[0064] On the other hand, when the control unit 25 changes the variance-like parameter, the communication quality determination unit 24 determines the reference quality value after the variance-like parameter is changed based on the average value after the variance-like parameter is changed and the margin value. The communication quality determination unit 24 determines the value obtained by subtracting the margin value from the average value after the variance-like parameter is changed as the reference quality value after the variance-like parameter is changed. When the variance-like parameter is changed, the slope of the straight line approximating the second cumulative distribution function remains the same. Therefore, the communication quality determination unit 24 determines the reference quality value after the parameter is changed by subtracting the margin value from the average value after the variance-like parameter is changed. The communication quality determination unit 24 stores the reference quality value after the parameter is changed in the storage unit 26 in association with the name of the parameter changed by the control unit 25 and the value before and after the change.

[0065] When the control unit 25 receives the parameter adjustment request, the control unit 25 changes the parameters in the optical communication path P2, which are related to the communication settings in the optical communication path P2. The control unit 25 changes the parameters so that the reference quality value after the parameter change satisfies the required quality value. The required quality value is a threshold value of communication quality information at which communication cannot be established in the optical communication path P2, and is a value of communication quality information at which a Frame Error Rate (FER), which indicates an error rate after error correction, becomes a predetermined value.

[0066] The control unit 25 determines whether the reference quality value determined by the communication quality determination unit 24 is greater than the required quality value, thereby determining whether the reference quality value determined by the communication quality determination unit 24 satisfies the required quality value. If the reference quality value satisfies the required quality value, the control unit 25 changes the parameters so that the reference quality value becomes lower. If the reference quality value does not satisfy the required quality value, the control unit 25 changes the parameters so that the reference quality value becomes higher. When the control unit 25 changes the parameters, it transmits the changed parameter name and the parameter values ​​before and after the change to the communication unit 21, the cumulative distribution estimation unit 23, and the communication quality determination unit 24.

[0067] When the reference quality value before the parameter change satisfies the required quality value and the control unit 25 changes the modulation method, the control unit 25 changes the modulation method so that the order of the modulation method is increased. When the modulation method before the parameter change is QPSK, the control unit 25 increases the order of the modulation method and changes the modulation method to 8QAM. When the modulation method before the parameter change is 8QAM, the control unit 25 increases the order of the modulation method and changes the modulation method to 16QAM. When the modulation method before the parameter change is 16QAM, the control unit 25 increases the order of the modulation method and changes the modulation method to 32QAM.

[0068] On the other hand, when the reference quality value before the parameter change does not satisfy the required quality value and the control unit 25 changes the modulation method, the control unit 25 changes the modulation method so that the order of the modulation method is reduced. When the modulation method before the parameter change is 32QAM, the control unit 25 reduces the order of the modulation method and changes the modulation method to 16QAM. When the modulation method before the parameter change is 16QAM, the control unit 25 reduces the order of the modulation method and changes the modulation method to 8QAM. When the modulation method before the parameter change is 8QAM, the control unit 25 reduces the order of the modulation method and changes the modulation method to QPSK.

[0069] When the reference quality value before the parameter change satisfies the required quality value and the control unit 25 changes the guard band, the control unit 25 changes the guard band so that the guard band is narrower than the current value. In other words, the control unit 25 changes the guard band for each communication channel so that the guard band is narrower than the current value and the bandwidth of each communication channel is wider, although interference with adjacent communication channels increases.

[0070] On the other hand, when the reference quality value before the parameter change does not satisfy the required quality value and the control unit 25 changes the guard band, the control unit 25 changes the guard band so that the guard band is wider than the current value. In other words, the control unit 25 changes the guard band for each communication channel so that the guard band is wider than the current value, the interference with adjacent communication channels is reduced, but the bandwidth of each communication channel is narrowed.

[0071] When the reference quality value before the parameter change satisfies the required quality value and the control unit 25 changes the optical transmission power in the optical communication path P2, the control unit 25 changes the optical transmission power so that the optical transmission power becomes smaller than the current value. In other words, the control unit 25 changes the optical transmission power so that the reference quality value becomes lower but the power consumption also decreases.

[0072] On the other hand, when the reference quality value before the parameter change does not satisfy the required quality value and the control unit 25 changes the optical transmission output in the optical communication path P2, the control unit 25 changes the optical transmission output so that the optical transmission output becomes larger than the current value. In other words, the control unit 25 changes the optical transmission output so that the reference quality value becomes higher, although the power consumption increases.

[0073] When the reference quality value before the parameter change satisfies the required quality value and the control unit 25 changes the number of communication channels in the optical communication path P2, the control unit 25 changes the number of communication channels so that the number of communication channels is increased from the current value. In other words, the control unit 25 changes the number of communication channels so that the reference quality value becomes lower but the communication capacity is increased.

[0074] On the other hand, when the reference quality value before the parameter change does not satisfy the required quality value and the control unit 25 changes the number of communication channels in the optical communication path P2, the control unit 25 changes the number of communication channels so that the number of communication channels is reduced from the current value. In other words, the control unit 25 changes the number of communication channels so that the communication capacity decreases but the reference quality value increases.

[0075] The storage unit 26 stores the calculated average value, gradient, margin value, reference quality value, changed parameter name, and values ​​before and after the change according to the control of the cumulative distribution estimation unit 23 and the communication quality determination unit 24.

[0076] <Example of optical transmission device operation> Next, an example of the operation of the optical transmission device according to the second embodiment will be described. First, an outline of the operation of the optical transmission device 20 according to the second embodiment will be described with reference to Fig. 4 to Fig. 6. Fig. 4 to Fig. 6 are diagrams illustrating an outline of the operation of the optical transmission device according to the second embodiment.

[0077] <Outline of operations when receiving a quality status confirmation request> 4 and 5, an overview of the operation of the optical transmission device 20 when the communication unit 21 receives a quality status check request will be described. When the communication unit 21 receives a quality status check request, the communication unit 21 transmits an acquisition request to the communication unit 31. The communication unit 21 receives a predetermined number of measurement values ​​acquired by the measurement unit 32 via the communication unit 31, and transmits the received measurement values ​​to the acquisition unit 22. When the acquisition unit 22 acquires the measurement values, the cumulative distribution estimation unit 23 generates a cumulative distribution for the communication quality information based on the acquired measurement values. FIG. 4 shows the cumulative distribution generated by the cumulative distribution estimation unit 23. As shown in FIG. 4, the horizontal axis represents the value of the Q value, which is an example of communication quality information, and the vertical axis represents the cumulative probability. The cumulative distribution estimation unit 23 plots the relationship between the value of the Q value, which is communication quality information, and the cumulative probability on the graph shown in FIG. 4 based on the acquired measurement values. The points shown in FIG. 4 are points representing the relationship between the Q value and the cumulative probability plotted by the cumulative distribution estimation unit 23. The cumulative distribution estimation unit 23 generates a curve L1 indicating a first cumulative distribution function by obtaining an approximation curve for the points plotted as the cumulative distribution using, for example, the least squares method. The cumulative distribution estimation unit 23 calculates the average value Q ave is calculated, and the slope of the first cumulative distribution function in a region where the cumulative probability changes sharply, such as a region where the cumulative probability is 0.1 to 0.9, is calculated.

[0078] Next, as shown in FIG. 5, the cumulative distribution estimation unit 23 calculates the Q value at which the cumulative probability is 0.5 by dividing the calculated average Q aveThe cumulative distribution estimation unit 23 determines a straight line L3 that passes through the point P1 where the calculated slope is the slope of the straight line. The cumulative distribution estimation unit 23 approximates the second cumulative distribution function in a region where the cumulative probability changes sharply in the curve L2 that indicates the second cumulative distribution function based on the measurement values ​​when more measurement values ​​than the number of acquired measurement values ​​are acquired, to the straight line L3. The dotted line L2 is a curve that indicates the second cumulative distribution function, and is a curve that indicates the cumulative distribution function when it is assumed that more measurement values ​​than the number of acquired measurement values ​​are acquired. The cumulative distribution estimation unit 23 determines the straight line L3 as an approximation straight line for a region of the dotted line L2 where the cumulative probability changes sharply, such as a region where the cumulative probability is 0.1 to 0.9. That is, the cumulative distribution estimation unit 23 estimates the second cumulative distribution function by approximating the curve L2 that indicates the unknown second cumulative distribution function with the known straight line L3. The communication quality determination unit 24 approximates Q, which is a value of communication quality information where the cumulative probability becomes a predetermined value on the straight line L3. wERR is determined as the reference quality value.

[0079] The control unit 25 determines the reference quality value Q wERR If the required quality value is satisfied, the reference quality value Q wERR The control unit 25 changes the parameters so that the reference quality value Q before the parameter change is lowered. wERR If the required quality value FL is not met, the reference quality value Q wERR Change the parameters so that it is higher.

[0080] <Outline of operation when parameter adjustment is requested and before parameter change> Next, when the communication unit 21 receives a parameter adjustment request and the control unit 25 has not changed the parameters, the optical transmission device 20 performs the same operation as when a quality status confirmation request is received. That is, when a parameter adjustment request is received from the communication unit 21 and the control unit 25 has not changed the parameters, the optical transmission device 20 performs the operation described with reference to FIGS. 4 and 5.

[0081] <Outline of operation when parameter adjustment is requested and variance dissimilarity parameters are changed> Next, when the communication unit 21 receives a parameter adjustment request and the control unit 25 changes the dispersion dissimilarity parameter, the optical transmission device 20 performs the same operation as when a quality status confirmation request is received. That is, when the control unit 25 changes the dispersion dissimilarity parameter, the optical transmission device 20 performs the operation described with reference to FIGS. 4 and 5.

[0082] <Outline of operation when parameter adjustment is requested and variance similarity parameters are changed> Next, an overview of the operation of the optical transmission device 20 when the communication unit 21 receives a parameter adjustment request and the control unit 25 changes the variance similarity parameter will be described with reference to FIG.

[0083] First, the cumulative distribution estimation unit 23 calculates the average value Q based on the measured value before the variance similarity parameter is changed. ave1 In this case, the cumulative distribution estimation unit 23 calculates the Q value at which the cumulative probability becomes 0.5 and calculates the slope in the region where the cumulative probability changes sharply in the first cumulative distribution function. ave1 Then, the communication quality determination unit 24 uses the line L31 to calculate the reference quality value Q wERR1 6, curve L21 represents the second cumulative distribution function based on the measured value before the variance similarity parameter is changed, and represents the second cumulative distribution function approximated by the cumulative distribution estimation unit 23 with a straight line L31.

[0084] Next, when the control unit 25 changes the variance-like parameter, the cumulative distribution estimation unit 23 calculates the average value of the measurement values ​​acquired after the parameter change. In addition, the cumulative distribution estimation unit 23 calculates the average value Q ave1 and the reference quality value Q wERR1 The communication quality determination unit 24 calculates the difference between the average value Q calculated after the variance similarity parameter is changed as the margin value Margin. ave2 The margin value Margin is subtracted from the standard quality value Q after the variance similarity parameter is changed. wERR2In addition, once the cumulative distribution estimation unit 23 determines the margin value Margin, the cumulative distribution estimation unit 23 can use the determined margin value Margin even if the variance similarity parameter is changed multiple times. Therefore, the cumulative distribution estimation unit 23 may determine the margin value Margin only once.

[0085] Here, when the variance similarity parameter is changed, the cumulative distribution estimation unit 23 can also determine the straight line L32 approximating the second cumulative distribution function, as in the case where the variance dissimilarity parameter is changed. However, the variance of the communication quality information value is the same before and after the variance similarity parameter is changed. In other words, the slope of the straight line L31 approximating the second cumulative distribution function before the parameter change is the same as the slope of the straight line L32 approximating the second cumulative distribution function after the parameter change. Therefore, when the variance similarity parameter is changed, the cumulative distribution estimation unit 23 does not calculate the slope of the straight line L32 approximating the second cumulative distribution function after the parameter change, but calculates the margin value Margin. Then, the communication quality determination unit 24 calculates the average value Q calculated after the variance similarity parameter is changed. ave2 The margin value Margin is subtracted from the standard quality value Q after the variance similarity parameter is changed. wERR2 In this way, when the variance similarity parameter is changed, the communication quality determination unit 24 determines the reference quality value Q by using a margin value that indicates the amount of shift between the line L31 and the line L32, which are approximation lines before and after the parameter change. wERR2 In addition, when the variance similarity parameter is changed, the communication quality determination unit 24 can instantly determine the reference quality value Q by simply performing subtraction processing using the average value and the margin value after the parameter change without calculating the straight line L32, which is the approximation straight line after the parameter change. wERR2 Therefore, the communication quality determining unit 24 can reduce the amount of calculation compared to when the variance dissimilarity parameter is changed.

[0086] <Example of operation 1 (Example of operation when receiving a quality status confirmation request)> Next, an example of the operation of the optical transmission device 20 when a quality status confirmation request is received will be described with reference to Fig. 7. Fig. 7 is a flowchart showing an example of the operation of the optical transmission device according to the second embodiment.

[0087] The communication unit 21 receives the quality status confirmation request (step S11). The communication unit 21 receives a quality status confirmation request from, for example, a network monitoring device (not shown). When the communication unit 21 receives the quality status confirmation request, it transmits an acquisition request to the communication unit 31. The communication unit 31 of the optical transmission device 30 receives the acquisition request and transmits the acquisition request to the measurement unit 32. The measurement unit 32 measures communication quality information in the optical communication path P2 and acquires a predetermined number or more of measurement values. The measurement unit 32 transmits the acquired predetermined number or more of measurement values ​​to the optical transmission device 20 via the communication unit 31.

[0088] The acquisition unit 22 acquires a predetermined number of measurement values ​​or more (step S12). After transmitting the acquisition request, the communication unit 21 receives the predetermined number or more of measurement values ​​acquired by the measurement unit 32 from the communication unit 31 via the optical communication path P2. The acquisition unit 22 acquires the predetermined number or more of measurement values ​​measured regarding the communication quality information in the optical communication path P2.

[0089] The cumulative distribution estimation unit 23 calculates the average value of the acquired measurement values ​​(step S13). The cumulative distribution estimation unit 23 generates a first cumulative distribution function (step S14). The cumulative distribution estimation unit 23 generates a first cumulative distribution function indicating a cumulative distribution function of communication quality information based on a predetermined number or more of acquired measurement values. The cumulative distribution estimation unit 23 generates a cumulative distribution in which the horizontal axis represents the quality value of communication quality information and the vertical axis represents the cumulative probability based on the acquired measurement values. The cumulative distribution estimation unit 23 generates the first cumulative distribution function by obtaining an approximation curve for the points plotted as the generated cumulative distribution using, for example, the least squares method.

[0090] The cumulative distribution estimation unit 23 calculates the slope of the first cumulative distribution function in a region where the cumulative probability changes sharply (step S15). The cumulative distribution estimation unit 23 calculates the slope of the first cumulative distribution function in a region where the cumulative probability changes sharply. The cumulative distribution estimation unit 23 calculates the slope of the first cumulative distribution function in a region where the cumulative probability changes sharply, such as a region where the cumulative probability is 0.1 to 0.9.

[0091] The cumulative distribution estimation unit 23 determines a straight line based on the calculated average value and the calculated slope (step S16). The cumulative distribution estimation unit 23 determines a straight line that passes through the point where the calculated average value is the communication quality information value with a cumulative probability of 0.5 and has the calculated slope. The cumulative distribution estimation unit 23 estimates the second cumulative distribution function by approximating the second cumulative distribution function in a region where the cumulative probability changes sharply to the determined straight line.

[0092] The communication quality determination unit 24 determines a reference quality value using the determined straight line (step S17). The communication quality determination unit 24 assumes that the reference quality value exists on the straight line determined in step S15, and determines the value of the communication quality information of a point on the straight line where the cumulative probability is a predetermined value as the reference quality value.

[0093] <Example of operation 2 (Example of operation when a parameter adjustment request is received)> Next, an operation example of the optical transmission device 20 when a parameter adjustment request is received will be described with reference to Fig. 8. Fig. 8 is a flowchart showing an operation example of the optical transmission device according to the second embodiment. Specifically, Fig. 8 is a flowchart showing an operation example when the optical transmission device 20 receives a parameter adjustment request, determines a reference quality value before a parameter is changed, and then changes a variance dissimilarity parameter and a variance similarity parameter.

[0094] Of the operations in Fig. 8, those common to Fig. 7 will be omitted as appropriate, with reference to Fig. 7. The state before the operation example in Fig. 8 is executed is a state in which the reference quality value satisfies the required quality value. In addition, the dispersion dissimilarity parameter is the modulation method in the optical communication path P2, and the dispersion similarity parameter is the optical transmission output in the optical communication path P2, but this is an example and is not limited to this. Fig. 8 shows an operation example in which two parameters are changed, but the number of parameters to be changed is not limited to two, and may be one, or three or more.

[0095] First, the communication unit 21 receives a parameter adjustment request (step S21). The communication unit 21 receives a parameter adjustment request from, for example, a network monitoring device (not shown). When the communication unit 21 receives the parameter adjustment request, it transmits an acquisition request to the communication unit 31. The communication unit 31 of the optical transmission device 30 receives the acquisition request and transmits the acquisition request to the measurement unit 32. The measurement unit 32 measures communication quality information in the optical communication path P2 and acquires a predetermined number or more of measurement values. The measurement unit 32 transmits the acquired predetermined number or more of measurement values ​​to the optical transmission device 20 via the communication unit 31.

[0096] The optical transmission device 20 performs a quality status confirmation operation (step S22). The quality status checking operation is the operations of steps S12 to S17 in the flowchart shown in Fig. 7. The acquisition unit 22 executes step S12 shown in Fig. 7, the cumulative distribution estimation unit 23 executes steps S13 to S16 shown in Fig. 7, and the communication quality determination unit 24 executes step S17.

[0097] Next, the control unit 25 increases the order of the modulation scheme in the optical communication path P2, which is a dispersion dissimilarity parameter (step S23). When the modulation method before changing the modulation method is QPSK, the control unit 25 changes the modulation method to 8QAM. When the modulation method before changing the modulation method is 8QAM, the control unit 25 changes the modulation method to 16QAM. When the modulation method before changing the modulation method is 16QAM, the control unit 25 changes the modulation method to 32QAM. That is, the control unit 25 executes control to increase the communication capacity by increasing the order of the modulation method by one, although the reference quality value deteriorates. Note that when the modulation method before changing the modulation method is 32QAM, the optical transmission device 20 may skip steps S24 and S25 and execute step S26.

[0098] The optical transmission device 20 performs a quality status confirmation operation (step S24). The acquisition unit 22 executes step S12 shown in FIG. 7, the cumulative distribution estimation unit 23 executes steps S13 to S16 shown in FIG. 7, and the communication quality determination unit 24 executes step S17.

[0099] The control unit 25 determines whether the reference quality value determined by the communication quality determining unit 24 is greater than the required quality value (step S25). If the reference quality value determined by the communication quality determining unit 24 is greater than the required quality value (YES in step S25), the optical transmission device 20 executes the operations in and after step S23. If the reference quality value determined by the communication quality determination unit 24 is not greater than the required quality value (NO in step S25), the control unit 25 decreases the order of the modulation method by one and changes the modulation method to one in which the reference quality value satisfies the required quality value (step S26). In other words, the control unit 25 executes control to decrease the order of the modulation method by one, thereby decreasing the communication capacity but recovering the reference quality value.

[0100] Next, the control unit 25 reduces the optical transmission output in the optical communication path P2, which is a dispersion-like parameter (step S27). The control unit 25 executes control to reduce the optical transmission output by, for example, 1 mW. That is, the control unit 25 executes control to increase the communication capacity by lowering the optical transmission output, although the reference quality value deteriorates. When the control unit 25 changes the optical transmission output, the communication unit 21 transmits an acquisition request to the communication unit 31. The communication unit 31 of the optical transmission device 30 receives the acquisition request and transmits the acquisition request to the measurement unit 32. The measurement unit 32 measures communication quality information in the optical communication path P2 and acquires a predetermined number or more of measurement values. The measurement unit 32 transmits the acquired predetermined number or more of measurement values ​​to the optical transmission device 20 via the communication unit 31.

[0101] The acquiring unit 22 acquires a predetermined number or more of measured values ​​(step S28). After transmitting the acquisition request, the communication unit 21 receives the predetermined number or more of measurement values ​​acquired by the measurement unit 32 from the communication unit 31 via the optical communication path P2. The acquisition unit 22 acquires the predetermined number or more of measurement values ​​measured regarding the communication quality information in the optical communication path P2.

[0102] The cumulative distribution estimation unit 23 calculates the average value of the measurement values ​​acquired after the optical transmission power is changed, and calculates the difference between the average value before the optical transmission power is changed and the reference quality value before the optical transmission power is changed as a margin value (step S29). Note that the margin value is not changed even when the variance similarity parameter is changed, so the cumulative distribution estimation unit 23 calculates the margin value only when step S29 is executed for the first time, and does not need to calculate the margin value when step S29 is executed for the second or subsequent times.

[0103] The communication quality determining unit 24 determines a value obtained by subtracting a margin value from the average value of the measurement values ​​acquired after the optical transmission output is changed as the reference quality value after the optical transmission output is changed (step S30).

[0104] The control unit 25 determines whether the reference quality value determined by the communication quality determining unit 24 is greater than the required quality value (step S31). If the reference quality value determined by the communication quality determining unit 24 is greater than the required quality value (YES in step S31), the optical transmission device 20 executes the operations in and after step S27. If the reference quality value determined by the communication quality determination unit 24 is not greater than the required quality value (NO in step S31), the control unit 25 executes control to increase the optical transmission output, for example, by 1 mW, and changes the reference quality value to the optical transmission output that satisfies the required quality value (step S32). That is, the control unit 25 executes control to increase the optical transmission output, which reduces the communication capacity, but restores the reference quality value. Then, the optical transmission device 20 ends the process.

[0105] <Example of operation 3 (Example of operation when a parameter adjustment request is received)> Next, an operation example of the optical transmission device 20 when a parameter adjustment request is received will be described with reference to Fig. 9. Fig. 9 is a flowchart showing an operation example of the optical transmission device according to the second embodiment. Specifically, Fig. 9 is a flowchart showing an operation example when the optical transmission device 20 receives a parameter adjustment request, determines a reference quality value before a parameter is changed, and then changes two variance similarity parameters.

[0106] Of the operations in Fig. 9, those common to Fig. 7 will be omitted as appropriate, with reference to Fig. 7. The state before the operation example in Fig. 9 is executed is a state in which the reference quality value satisfies the required quality value. In addition, the first dispersion-like parameter will be described as the number of communication channels in the optical communication path P2, and the second dispersion-like parameter will be described as the optical transmission output in the optical communication path P2, but this is only an example and is not limited to this. Fig. 9 shows an operation example in which two parameters are changed, but the number of parameters to be changed is not limited to two, and may be one, or three or more.

[0107] First, the communication unit 21 receives a parameter adjustment request (step S41). The communication unit 21 receives a parameter adjustment request from, for example, a network monitoring device (not shown). When the communication unit 21 receives the parameter adjustment request, it transmits an acquisition request to the communication unit 31. The communication unit 31 of the optical transmission device 30 receives the acquisition request and transmits the acquisition request to the measurement unit 32. The measurement unit 32 measures communication quality information in the optical communication path P2 and acquires a predetermined number or more of measurement values. The measurement unit 32 transmits the acquired predetermined number or more of measurement values ​​to the optical transmission device 20 via the communication unit 31.

[0108] The optical transmission device 20 performs a quality status confirmation operation (step S42). The quality status checking operation is the operations of steps S12 to S17 in the flowchart shown in Fig. 7. The acquisition unit 22 executes step S12 shown in Fig. 7, the cumulative distribution estimation unit 23 executes steps S13 to S16 shown in Fig. 7, and the communication quality determination unit 24 executes step S17.

[0109] Next, the control unit 25 increases the number of communication channels in the optical communication path P2, which is the first dispersion-like parameter (step S43). The control unit 25 executes control to increase the number of communication channels in the optical communication path P2 by one. That is, the control unit 25 executes control to increase the communication capacity by increasing the number of communication channels, although the reference quality value deteriorates. When the control unit 25 changes the number of communication channels, the communication unit 21 transmits an acquisition request to the communication unit 31. The communication unit 31 of the optical transmission device 30 receives the acquisition request and transmits the acquisition request to the measurement unit 32. The measurement unit 32 measures communication quality information in the optical communication path P2 and acquires a predetermined number or more of measured values. The measurement unit 32 transmits the acquired predetermined number or more of measured values ​​to the optical transmission device 20 via the communication unit 31.

[0110] The acquiring unit 22 acquires a predetermined number or more of measured values ​​(step S44). After transmitting the acquisition request, the communication unit 21 receives the predetermined number or more of measurement values ​​acquired by the measurement unit 32 from the communication unit 31 via the optical communication path P2. The acquisition unit 22 acquires the predetermined number or more of measurement values ​​measured regarding the communication quality information in the optical communication path P2.

[0111] The cumulative distribution estimation unit 23 calculates the average value of the measurement values ​​acquired after the number of communication channels is changed, and calculates the difference between the average value before the number of communication channels is changed and the reference quality value before the number of communication channels is changed as a margin value (step S45). Note that since the margin value is not changed even when the variance similarity parameter is changed, the cumulative distribution estimation unit 23 calculates the margin value only when step S45 is executed for the first time, and does not calculate the margin value when step S45 is executed for the second or subsequent times.

[0112] The communication quality determination unit 24 determines the value obtained by subtracting the margin value from the average value of the measurement values ​​obtained after the number of communication channels is changed as the reference quality value after the number of communication channels is changed (step S46).

[0113] The control unit 25 determines whether the reference quality value determined by the communication quality determining unit 24 is greater than the required quality value (step S47). If the reference quality value determined by the communication quality determining unit 24 is greater than the required quality value (YES in step S47), the optical transmission device 20 executes the operations in and after step S43. If the reference quality value determined by the communication quality determination unit 24 is not greater than the required quality value (NO in step S47), the control unit 25 executes control to decrease the number of communication channels by one, and changes the reference quality value to the number of communication channels that satisfies the required quality value (step S32). In other words, by decreasing the number of communication channels by one, the communication capacity decreases, but the control unit 25 executes control to restore the reference quality value.

[0114] Next, the control unit 25 decreases the optical transmission output in the optical communication path P2, which is the second dispersion-like parameter (step S49). The control unit 25 executes control to reduce the optical transmission output by, for example, 1 mW. That is, the control unit 25 executes control to increase the communication capacity by lowering the optical transmission output, although the reference quality value deteriorates. When the control unit 25 changes the optical transmission output, the communication unit 21 transmits an acquisition request to the communication unit 31. The communication unit 31 of the optical transmission device 30 receives the acquisition request and transmits the acquisition request to the measurement unit 32. The measurement unit 32 measures communication quality information in the optical communication path P2 and acquires a predetermined number or more of measurement values. The measurement unit 32 transmits the acquired predetermined number or more of measurement values ​​to the optical transmission device 20 via the communication unit 31.

[0115] The acquisition unit 22 acquires a predetermined number of measurement values ​​or more (step S50). After transmitting the acquisition request, the communication unit 21 receives the predetermined number or more of measurement values ​​acquired by the measurement unit 32 from the communication unit 31 via the optical communication path P2. The acquisition unit 22 acquires the predetermined number or more of measurement values ​​measured regarding the communication quality information in the optical communication path P2.

[0116] The cumulative distribution estimation unit 23 calculates the average value of the measurement values ​​acquired after the optical transmission output is changed (step S51). Note that since the cumulative distribution estimation unit 23 calculates the margin value at the timing when step S45 is first executed, the cumulative distribution estimation unit 23 does not calculate the margin value in step S51.

[0117] The communication quality determining unit 24 determines a value obtained by subtracting a margin value from the average value of the measurement values ​​acquired after the optical transmission output is changed as the reference quality value after the optical transmission output is changed (step S52).

[0118] The control unit 25 determines whether the reference quality value determined by the communication quality determining unit 24 is greater than the required quality value (step S53). If the reference quality value determined by the communication quality determining unit 24 is greater than the required quality value (YES in step S53), the optical transmission device 20 executes the operations in and after step S49. If the reference quality value determined by the communication quality determination unit 24 is not greater than the required quality value (NO in step S53), the control unit 25 executes control to increase the optical transmission output, for example, by 1 mW, and changes the reference quality value to the optical transmission output that satisfies the required quality value (step S54). That is, the control unit 25 executes control to increase the optical transmission output, which reduces the communication capacity, but restores the reference quality value. Then, the optical transmission device 20 ends the process.

[0119] As described above, the optical transmission device 20 can determine a reference quality value for a case where more measurement values ​​than the number of measurement values ​​actually measured are acquired based on the measurement values ​​of the communication quality information, similarly to the first embodiment. Therefore, by using the optical transmission device 20, the telecommunications carrier can determine a reference quality value for a case where a large number of measurement values ​​are acquired, without acquiring a large number of measurement values. In other words, by using the optical transmission device 20, the telecommunications carrier can determine a reference quality value for a measurement value that is predicted to be acquired in a total measurement time longer than the total measurement time actually measured, based on the measurement values ​​acquired in a short total measurement time. Therefore, the optical transmission device 20 according to the second embodiment allows the telecommunications carrier to easily grasp the communication quality situation.

[0120] Furthermore, the control unit 25 uses the reference quality value determined based on the measurement value of the communication quality information to control parameters related to communication settings in the optical communication path P2 so that the reference quality value satisfies the required quality value. The cumulative distribution estimation unit 23 and the communication quality determination unit 24 can determine the reference quality value when a large number of measurement values ​​are acquired without acquiring a large number of measurement values, and the control unit 25 can control the parameters related to communication settings to be optimal values ​​using the determined reference quality value. That is, by using the optical transmission device 20, the communication carrier can determine optimal parameter values ​​without acquiring a large number of measurement values. Therefore, the optical transmission device 20 according to the second embodiment allows the communication carrier to instantly determine optimal parameter values.

[0121] Furthermore, when the control unit 25 changes the variance-like parameter, the cumulative distribution estimation unit 23 calculates the average value of the measurement values ​​acquired after the parameter is changed and the margin value. Then, the communication quality determination unit 24 can determine the reference quality value after the variance-like parameter is changed based on the calculated average value and the margin value. In other words, the cumulative distribution estimation unit 23 can determine the reference quality value after the variance-like parameter is changed without approximating the second cumulative distribution function with a straight line based on the average value of the acquired measurement values ​​and the slope of the first cumulative distribution function. Therefore, according to the optical transmission device 20 according to the second embodiment, when the variance-like parameter is changed, the communication quality status can be immediately and easily grasped.

[0122] (Modification) When the variance-like parameter is changed, the cumulative distribution estimation unit 23 may calculate the difference between a first average value indicating the average value of the measurement values ​​acquired after the parameter is changed and a second average value indicating the average value of the measurement values ​​acquired before the parameter is changed, without calculating the margin value. Then, the communication quality determination unit 24 may determine the reference quality value after the variance-like parameter is changed based on the first reference quality value indicating the reference quality value before the variance-like parameter is changed and the difference. When the first average value is greater than the second average value, the communication quality determination unit 24 may determine the value obtained by adding the difference to the first reference quality value as the reference quality value after the variance-like parameter is changed. Also, when the first average value is smaller than the second average value, the communication quality determination unit 24 may determine the value obtained by subtracting the difference from the first reference quality value as the reference quality value after the variance-like parameter is changed. In this way, even if the second embodiment is modified, the same effect as that of the second embodiment can be obtained.

[0123] (Embodiment 3) Next, a description will be given of embodiment 3. In embodiment 3, the process performed by the optical transmission device 20 in embodiment 2 is performed by a network monitoring device.

[0124] <Example of optical communication system configuration> A configuration example of an optical communication system 200 according to the third embodiment will be described with reference to Fig. 10. Fig. 10 is a diagram illustrating a configuration example of an optical communication system according to the third embodiment. The optical communication system 200 includes a terminal device 10, a network monitoring device 50, and optical transmission devices 60 and 70.

[0125] The optical communication system 200 has a configuration in which a network monitoring device 50 is added to the optical communication system 100 according to the second embodiment. Also, the optical communication system 200 has a configuration in which the optical transmission devices 20 and 30 in the optical communication system 100 according to the second embodiment are replaced with optical transmission devices 60 and 70, respectively. Note that the configurations of the terminal devices 10 and 40 are basically the same as those in the second embodiment, and therefore will not be described as appropriate.

[0126] The network monitoring device 50 is a device that monitors the entire network of the optical communication system 200. The network monitoring device 50 may be referred to as an NMS (Network Management System). The network monitoring device 50 is connected to the optical transmission devices 60 and 70 via a network N, and communicates with the optical transmission devices 60 and 70. The network monitoring device 50 monitors the optical transmission devices 60 and 70, and controls the optical transmission devices 60 and 70 via the network N.

[0127] <Network monitoring device configuration example> Next, a configuration example of the network monitoring device 50 will be described. The network monitoring device 50 includes a communication unit 51, an acquisition unit 52, a cumulative distribution estimation unit 53, a communication quality determination unit 54, a control unit 55, and a storage unit 56. The acquisition unit 52, the cumulative distribution estimation unit 53, the communication quality determination unit 54, the control unit 55, and the storage unit 56 are basically configured similarly to the acquisition unit 22, the cumulative distribution estimation unit 23, the communication quality determination unit 24, the control unit 25, and the storage unit 56 in the second embodiment, respectively. Therefore, the description of the configuration examples of the acquisition unit 52, the cumulative distribution estimation unit 53, the communication quality determination unit 54, the control unit 55, and the storage unit 56 that are similar to those in the second embodiment will be omitted as appropriate.

[0128] The communication unit 51 receives a quality status confirmation request and a parameter adjustment request. The communication unit 51 is configured to include an input device such as a keyboard, a mouse, a touch panel, etc., and receives (inputs) a quality status confirmation request and a parameter adjustment request input by an operator who maintains and manages the optical communication path P2 using the input device. The communication unit 51 transmits the quality status confirmation request and the parameter adjustment request to the cumulative distribution estimation unit 53 and the communication quality determination unit 54. The communication unit 51 also transmits the parameter adjustment request to the control unit 55.

[0129] When the communication unit 51 receives a quality status confirmation request, it transmits an acquisition request to the communication unit 71 of the optical transmission device 70 via the network N. When the communication unit 51 receives a parameter adjustment request, it transmits the acquisition request to the communication unit 71 via the network N. Furthermore, when the communication unit 51 receives a parameter adjustment request, the control unit 55 changes parameters in consideration of the communication quality status in the optical communication path P2. The communication unit 51 transmits an acquisition request to the communication unit 71 via the network N every time the control unit 55 changes a parameter.

[0130] After transmitting the acquisition request, the communication unit 51 receives the predetermined number or more of measurement values ​​acquired by the measurement unit 32 from the communication unit 71 via the network N. The communication unit 51 outputs the received predetermined number or more of measurement values ​​to the acquisition unit 52.

[0131] The acquiring unit 52 acquires from the measuring unit 32 via the communication units 51 and 71 a predetermined number or more of measured values ​​of the communication quality information in the optical communication path P2. The cumulative distribution estimation unit 53 has a similar configuration to the cumulative distribution estimation unit 23 according to the second embodiment, and executes the process performed by the cumulative distribution estimation unit 23 according to the second embodiment. The communication quality determining unit 54 has a similar configuration to the communication quality determining unit 24 according to the second embodiment, and executes the processing performed by the communication quality determining unit 24 according to the second embodiment.

[0132] The control unit 55 has a configuration basically similar to that of the control unit 25 according to the second embodiment. When the control unit 55 receives a parameter adjustment request, the control unit 55 changes the parameters in the optical communication path P2, which are related to the communication settings in the optical communication path P2, via the control unit 62 of the optical transmission device 60. The control unit 55 transmits the names of the parameters to be changed and the parameter values ​​after the change to the control unit 62 via the communication units 51 and 61, and changes the parameters by having the control unit 62 change the parameters. The control unit 55 changes the parameters so that the reference quality value after the parameters are changed satisfies the required quality value.

[0133] The storage unit 56 has a similar configuration to the storage unit 26 according to the second embodiment, and executes the processes performed by the storage unit 26 according to the second embodiment.

[0134] <Example of optical transmission device configuration> Next, a description will be given of an example of the configuration of the optical transmission device 60. The optical transmission device 60 includes a communication unit 61 and a control unit 62.

[0135] The communication unit 61 has a configuration basically similar to that of the communication unit 21 according to the second embodiment. The communication unit 61 communicates with the terminal device 10 and with the optical transmission device 70. The communication unit 61 receives an optical communication signal from the optical transmission device 70 via the optical communication path P2, and restores a data unit based on a bit string included in the optical communication signal. The communication unit 61 extracts a communication frame from the data unit and transmits it to the terminal device 10 via the communication path P1. The communication unit 61 receives a communication frame from the terminal device 10 via the communication path P1. The communication unit 61 stores the received communication frame in a data unit and converts the data unit into an optical communication signal. The communication unit 61 transmits the optical communication signal to the optical transmission device 70 via the optical communication path P2.

[0136] The communication unit 61 receives the parameter name to be changed by the control unit 55 and the changed parameter value from the control unit 55 via the communication unit 51, and transmits the parameter name and the changed parameter value to the control unit 62.

[0137] The control unit 62 changes parameters related to communication settings, which are parameters in the optical communication path P2, in response to the control of the control unit 55. The control unit 62 receives the parameter names to be changed by the control unit 55 and the parameter values ​​after the change via the communication unit 61. The control unit 62 changes the received parameter names to the parameter values ​​after the change.

[0138] The optical transmission device 70 includes a communication unit 71 and a measurement unit 32. The configuration of the measurement unit 32 is the same as that in the second embodiment, and therefore a description thereof will be omitted. The communication unit 71 has a configuration basically similar to that of the communication unit 31 according to the second embodiment. The communication unit 71 communicates with the terminal device 40 and with the optical transmission device 60. The communication unit 71 receives an optical communication signal from the optical transmission device 60 via the optical communication path P2, and restores a data unit based on a bit string included in the optical communication signal. The communication unit 71 extracts a communication frame from the data unit and transmits it to the terminal device 40 via the communication path P3. The communication unit 71 receives the communication frame from the terminal device 40 via the communication path P3. The communication unit 71 stores the received communication frame in a data unit and converts the data unit into an optical communication signal. The communication unit 71 transmits the optical communication signal to the optical transmission device 60 via the optical communication path P2.

[0139] The communication unit 71 receives an acquisition request from the network monitoring device 50 via the network N, and notifies (transmits) the measurement unit 32 of the receipt of the acquisition request. The communication unit 71 transmits the multiple measurement values ​​acquired by the measurement unit 32 to the network monitoring device 50 via the network N.

[0140] <Example of network monitoring device operation> Next, an operation example of the network monitoring device 50 will be described. The network monitoring device 50 executes the same operation as that executed by the optical transmission device 20 according to the second embodiment. Therefore, the operation example of the network monitoring device 50 will be described with reference to Figs. 7 to 9, while omitting appropriate explanations.

[0141] <Example of operation 1 (Example of operation when receiving a quality status confirmation request)> Next, an example of the operation of the network monitoring device 50 when a quality status confirmation request is received (input) will be described with reference to FIG.

[0142] The communication unit 51 receives the quality status confirmation request (step S11). The communication unit 51 receives (inputs) a quality status confirmation request that is input by an operator who maintains and manages the optical communication path P2 using an input device. When the communication unit 51 receives a quality status confirmation request, it transmits an acquisition request to the communication unit 71 via the network N. The communication unit 71 of the optical transmission device 70 receives the acquisition request and transmits the acquisition request to the measurement unit 32. The measurement unit 32 measures communication quality information in the optical communication path P2 and acquires a predetermined number or more of measurement values. The measurement unit 32 transmits the acquired predetermined number or more of measurement values ​​to the network monitoring device 50 via the communication unit 71.

[0143] The acquiring unit 52 acquires a predetermined number or more of measured values ​​(step S12). The cumulative distribution estimation unit 53 calculates the average value of the acquired measurement values ​​(step S13), and generates a first cumulative distribution function (step S14).

[0144] The cumulative distribution estimation unit 53 calculates the slope of the first cumulative distribution function in a region where the cumulative probability changes sharply (step S15), and determines a straight line based on the calculated average value and the calculated slope (step S16). The communication quality determination unit 54 determines a reference quality value using the determined straight line (step S17).

[0145] <Example of operation 2 (Example of operation when a parameter adjustment request is received)> Next, referring to Fig. 8, an operation example of the network monitoring device 50 when a parameter adjustment request is received will be described. Referring to Fig. 8, a flowchart is shown showing an operation example when the network monitoring device 50 receives a parameter adjustment request, determines a reference quality value before changing a parameter, and then changes a dispersion dissimilarity parameter and a dispersion similarity parameter. Of the operations in Fig. 8, the description of the operations common to Fig. 7 will be omitted as appropriate, with reference to Fig. 7. In this embodiment as well, the state before the operation example in Fig. 8 is executed is a state in which the reference quality value satisfies a required quality value, the dispersion dissimilarity parameter is a modulation method, and the dispersion similarity parameter is an optical transmission output. Note that, in this embodiment as well, the number of parameters to be changed is not limited to two, and may be one, or may be three or more.

[0146] First, the communication unit 51 receives a parameter adjustment request (step S21). The communication unit 51 receives (inputs) a parameter adjustment request input by an operator who maintains and manages the optical communication path P2 using an input device. When the communication unit 51 receives a parameter adjustment request, it transmits an acquisition request to the communication unit 71 via the network N. The communication unit 71 of the optical transmission device 70 receives the acquisition request and transmits the acquisition request to the measurement unit 32. The measurement unit 32 measures communication quality information in the optical communication path P2 and acquires a predetermined number or more of measurement values. The measurement unit 32 transmits the acquired predetermined number or more of measurement values ​​to the network monitoring device 50 via the communication unit 71.

[0147] The network monitoring device 50 performs a quality status confirmation operation (step S22). The acquisition unit 52 executes step S12 shown in FIG. 7, the cumulative distribution estimation unit 53 executes steps S13 to S16 shown in FIG. 7, and the communication quality determination unit 54 executes step S17.

[0148] Next, the control unit 55 increases the order of the modulation scheme in the optical communication path P2, which is a dispersion dissimilarity parameter (step S23). When the modulation method before changing the modulation method is QPSK, the control unit 55 changes the modulation method to 8QAM. When the modulation method before changing the modulation method is 8QAM, the control unit 25 changes the modulation method to 16QAM. When the modulation method before changing the modulation method is 16QAM, the control unit 25 changes the modulation method to 32QAM. The control unit 55 transmits the name of the parameter to be changed to the modulation method and the changed modulation method, which is the changed parameter value, to the control unit 62 via the communication units 51 and 61, and changes the modulation method by having the control unit 62 execute the change of the modulation method. The control unit 62 receives the name of the parameter to be changed to the modulation method and the changed modulation method, which is the changed parameter value, and changes the modulation method to the changed modulation method. Note that when the modulation method before changing the modulation method is 32QAM, the network monitoring device 50 may skip steps S24 and S25 and execute step S26.

[0149] The network monitoring device 50 performs a quality status confirmation operation (step S24). The acquisition unit 52 executes step S12 shown in FIG. 7, the cumulative distribution estimation unit 53 executes steps S13 to S16 shown in FIG. 7, and the communication quality determination unit 54 executes step S17.

[0150] The control unit 55 determines whether the reference quality value determined by the communication quality determining unit 54 is greater than the required quality value (step S25). If the reference quality value determined by the communication quality determination unit 54 is greater than the required quality value (YES in step S25), the network monitoring device 50 executes the operations in and after step S23. If the reference quality value determined by the communication quality determination unit 54 is not greater than the required quality value (NO in step S25), the control unit 55 decreases the order of the modulation method by one and changes the modulation method to one in which the reference quality value satisfies the required quality value (step S26). The control unit 55 transmits the name of the parameter to be changed, that is, the modulation method, and the changed parameter value, that is, the changed modulation method, to the control unit 62 via the communication units 51 and 61, and changes the modulation method by having the control unit 62 execute the change of the modulation method. The control unit 62 receives the name of the parameter to be changed, that is, the modulation method, and the changed parameter value, and changes the modulation method to the changed modulation method.

[0151] Next, the control unit 55 reduces the optical transmission output in the optical communication path P2, which is a dispersion-like parameter (step S27). The control unit 55 executes control to reduce the optical transmission output by, for example, 1 mW. The control unit 55 transmits to the control unit 62 via the communication units 51 and 61 information that the parameter name to be changed is the optical transmission output, and the value of the optical transmission output after the change, which is the parameter value after the change, and changes the optical transmission output by having the control unit 62 execute the change of the optical transmission output. The control unit 62 receives information that the parameter name to be changed is the optical transmission output, and the value of the optical transmission output after the change, and changes the value of the optical transmission output to the value of the optical transmission output after the change. When the control unit 55 changes the optical transmission output, the communication unit 51 transmits an acquisition request to the communication unit 71. The communication unit 71 receives the acquisition request, and transmits the acquisition request to the measurement unit 32. The measurement unit 32 measures communication quality information in the optical communication path P2 and acquires a predetermined number or more of measured values. The measurement unit 32 transmits the acquired predetermined number or more of measured values ​​to the network monitoring device 50 via the communication unit 71.

[0152] The acquiring unit 52 acquires a predetermined number or more of measured values ​​(step S28). The cumulative distribution estimation unit 53 calculates the average value of the measurement values ​​acquired after the optical transmission power is changed, and calculates the difference between the average value before the optical transmission power is changed and the reference quality value before the optical transmission power is changed as a margin value (step S29). Note that the cumulative distribution estimation unit 53 calculates the margin value only when step S29 is executed for the first time, and does not need to calculate the margin value when step S29 is executed for the second or subsequent times.

[0153] The communication quality determination unit 54 determines a value obtained by subtracting a margin value from the average value of the measurement values ​​acquired after the optical transmission output is changed as the reference quality value after the optical transmission output is changed (step S30).

[0154] The control unit 55 determines whether the reference quality value determined by the communication quality determination unit 54 is greater than the required quality value (step S31). If the reference quality value determined by the communication quality determination unit 54 is greater than the required quality value (YES in step S31), the network monitoring device 50 executes the operations in and after step S27. If the reference quality value determined by the communication quality determination unit 54 is not greater than the required quality value (NO in step S31), the control unit 55 executes control to increase the optical transmission output, for example, by 1 mW, and changes the reference quality value to the optical transmission output that satisfies the required quality value (step S32). The control unit 55 transmits to the control unit 62 via the communication units 51 and 61 the name of the parameter to be changed, that is, the optical transmission output, and the value of the optical transmission output after the change, and changes the optical transmission output by having the control unit 62 execute the change of the optical transmission output. The control unit 62 receives the name of the parameter to be changed, that is, the optical transmission output, and the value of the optical transmission output after the change, and changes the value of the optical transmission output to the value of the optical transmission output after the change. Then, the network monitoring device 50 ends the process.

[0155] <Example of operation 3 (Example of operation when a parameter adjustment request is received)> Next, referring to FIG. 9, an operation example of the network monitoring device 50 when a parameter adjustment request is received will be described. Referring to FIG. 9, a flowchart is shown showing an operation example when the network monitoring device 50 receives a parameter adjustment request, determines a reference quality value before changing a parameter, and then changes two variance-like parameters. Among the operations in FIG. 9, the description of the operations common to FIG. 7 will be omitted as appropriate, with reference to FIG. 7. The state before the operation example in FIG. 9 is executed is a state in which the reference quality value satisfies a required quality value. In addition, the first variance-like parameter is the number of communication channels in the optical communication path P2, and the second variance-like parameter is the optical transmission output in the optical communication path P2. FIG. 9 shows an operation example when two parameters are changed, but the number of parameters to be changed is not limited to two, and may be one, or may be three or more.

[0156] First, the communication unit 51 receives a parameter adjustment request (step S41). The communication unit 51 receives (inputs) a parameter adjustment request input by an operator who maintains and manages the optical communication path P2 using an input device. When the communication unit 51 receives a parameter adjustment request, it transmits an acquisition request to the communication unit 71 via the network N. The communication unit 71 of the optical transmission device 70 receives the acquisition request and transmits the acquisition request to the measurement unit 32. The measurement unit 32 measures communication quality information in the optical communication path P2 and acquires a predetermined number or more of measurement values. The measurement unit 32 transmits the acquired predetermined number or more of measurement values ​​to the network monitoring device 50 via the communication unit 71.

[0157] The network monitoring device 50 performs a quality status confirmation operation (step S42). The acquisition unit 52 executes step S12 shown in FIG. 7, the cumulative distribution estimation unit 53 executes steps S13 to S16 shown in FIG. 7, and the communication quality determination unit 54 executes step S17.

[0158] Next, the control unit 55 increases the number of communication channels in the optical communication path P2, which is the first dispersion-like parameter (step S43). The control unit 55 executes control to increase the number of communication channels in the optical communication path P2 by one. The control unit 55 transmits the name of the parameter to be changed to the number of communication channels and the changed number of communication channels, which is the parameter value after the change, to the control unit 62 via the communication units 51 and 61, and changes the number of communication channels by having the control unit 62 execute the change of the number of communication channels. The control unit 62 receives the name of the parameter to be changed to the number of communication channels and the changed number of communication channels, and changes the number of communication channels to the changed number of communication channels. When the control unit 55 changes the number of communication channels, the communication unit 51 transmits an acquisition request to the communication unit 71 via the network N. The communication unit 71 of the optical transmission device 70 receives the acquisition request and transmits the acquisition request to the measurement unit 32. The measurement unit 32 measures communication quality information in the optical communication path P2 and acquires a predetermined number or more of measured values. The measurement unit 32 transmits the acquired measured values ​​of the predetermined number or more to the network monitoring device 50 via the communication unit 71.

[0159] The acquiring unit 52 acquires a predetermined number or more of measured values ​​(step S44). The cumulative distribution estimation unit 53 calculates the average value of the measurement values ​​acquired after the number of communication channels is changed, and calculates the difference between the average value before the number of communication channels is changed and the reference quality value before the number of communication channels is changed as a margin value (step S45). Note that the cumulative distribution estimation unit 53 calculates the margin value only when step S45 is executed for the first time, and does not need to calculate the margin value when step S45 is executed for the second or subsequent times.

[0160] The communication quality determination unit 54 determines the value obtained by subtracting the margin value from the average value of the measurement values ​​obtained after the number of communication channels is changed as the reference quality value after the number of communication channels is changed (step S46).

[0161] The control unit 55 determines whether the reference quality value determined by the communication quality determining unit 54 is greater than the required quality value (step S47). If the reference quality value determined by the communication quality determination unit 54 is greater than the required quality value (YES in step S47), the network monitoring device 50 executes the operations in and after step S43. If the reference quality value determined by the communication quality determination unit 54 is not greater than the required quality value (NO in step S47), the control unit 55 executes control to reduce the number of communication channels by one, and changes the reference quality value to the number of communication channels that satisfies the required quality value (step S32). The control unit 55 changes the number of communication channels by transmitting the name of the parameter to be changed, that is, the number of communication channels, and the changed number of communication channels to the control unit 62 via the communication units 51 and 61, and having the control unit 62 change the number of communication channels. The control unit 62 receives the information that the name of the parameter to be changed, that is, the number of communication channels, and the changed number of communication channels, and changes the number of communication channels to the changed number of communication channels.

[0162] The control unit 55 reduces the optical transmission output in the optical communication path P2, which is the second dispersion-like parameter (step S49). The control unit 25 executes control to reduce the optical transmission output by, for example, 1 mW. The control unit 55 transmits to the control unit 62 via the communication units 51 and 61 information that the parameter name to be changed is the number of communication channels, and the changed parameter value, the changed number of communication channels, and changes the number of communication channels by having the control unit 62 execute the change of the number of communication channels. The control unit 62 receives information that the parameter name to be changed is the number of communication channels, and the changed number of communication channels, and changes the number of communication channels to the changed number of communication channels. When the control unit 55 changes the optical transmission output, the communication unit 51 transmits an acquisition request to the communication unit 71 via the network N. The communication unit 71 receives the acquisition request, and transmits the acquisition request to the measurement unit 32. The measurement unit 32 measures communication quality information in the optical communication path P2 and acquires a predetermined number or more of measured values. The measurement unit 32 transmits the acquired predetermined number or more of measured values ​​to the network monitoring device 50 via the communication unit 71.

[0163] The acquisition unit 52 acquires a predetermined number of measurement values ​​or more (step S50). The cumulative distribution estimation unit 53 calculates the average value of the measurement values ​​acquired after the optical transmission output is changed (step S51). The communication quality determination unit 54 determines a value obtained by subtracting a margin value from the average value of the measurement values ​​acquired after the optical transmission output is changed as the reference quality value after the optical transmission output is changed (step S52).

[0164] The control unit 55 determines whether the reference quality value determined by the communication quality determination unit 54 is greater than the required quality value (step S53). If the reference quality value determined by the communication quality determination unit 54 is greater than the required quality value (YES in step S53), the network monitoring device 50 executes the operations in and after step S49. If the reference quality value determined by the communication quality determination unit 54 is not greater than the required quality value (NO in step S53), the control unit 55 executes control to increase the optical transmission output, for example, by 1 mW, and changes the reference quality value to the optical transmission output that satisfies the required quality value (step S54). The control unit 55 transmits to the control unit 62 via the communication units 51 and 61 the name of the parameter to be changed, that is, the optical transmission output, and the value of the optical transmission output after the change, and changes the optical transmission output by having the control unit 62 execute the change of the optical transmission output. The control unit 62 receives the name of the parameter to be changed, that is, the optical transmission output, and the value of the optical transmission output after the change, and changes the value of the optical transmission output to the value of the optical transmission output after the change. Then, the network monitoring device 50 ends the process.

[0165] As described above, even if the network monitoring device 50 has the configuration of the optical transmission device 20 according to the second embodiment and executes the operations performed by the optical transmission device 20 according to the second embodiment, the same effects as those of the second embodiment can be obtained.

[0166] (Other embodiments) Fig. 11 is a block diagram showing an example of a hardware configuration of the communication device 1, the optical transmission devices 20, 30, 60, 70, and the network monitoring device 50 (hereinafter referred to as the communication device 1, etc.) described in the above-mentioned embodiment. Referring to Fig. 11, the communication device 1, etc. includes a network interface 1201, a processor 1202, and a memory 1203. The network interface 1201 is used to communicate with other communication devices included in the optical communication system, such as the optical transmission device, the terminal device, and the network monitoring device.

[0167] The processor 1202 reads out and executes software (computer programs) from the memory 1203 to perform the processing of the communication device 1 and the like described using the flowcharts in the above-mentioned embodiments. The processor 1202 may be, for example, a microprocessor, an MPU (Micro Processing Unit), or a CPU (Central Processing Unit). The processor 1202 may include multiple processors.

[0168] The memory 1203 is configured by a combination of volatile memory and non-volatile memory. The memory 1203 may include storage located remotely from the processor 1202. In this case, the processor 1202 may access the memory 1203 via an I / O (Input / Output) interface (not shown).

[0169] 11, the memory 1203 is used to store software modules. The processor 1202 reads out and executes the software modules from the memory 1203, thereby performing the processing of the communication device 1 and the like described in the above-mentioned embodiment.

[0170] As described with reference to FIG. 11, each of the processors included in the communication device 1 etc. executes one or more programs including a set of instructions for causing a computer to execute the algorithm described with reference to the drawing.

[0171] In the above example, the program can be stored and provided to the computer using various types of non-transitory computer readable media. The non-transitory computer readable media includes various types of tangible storage media. Examples of the non-transitory computer readable media include magnetic recording media (e.g., flexible disks, magnetic tapes, hard disk drives) and magneto-optical recording media (e.g., magneto-optical disks). Further, examples of the non-transitory computer readable media include CD-ROM (Read Only Memory), CD-R, and CD-R / W. Further, examples of the non-transitory computer readable media include semiconductor memory. The semiconductor memory includes, for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, and RAM (Random Access Memory). The program may also be provided to the computer by various types of transitory computer readable media. Examples of the transitory computer readable media include electrical signals, optical communication signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire or an optical fiber, or via a wireless communication path.

[0172] The present disclosure is not limited to the above-described embodiment, and may be modified as appropriate without departing from the spirit and scope of the present disclosure. In addition, the present disclosure may be implemented by appropriately combining the respective embodiments.

[0173] Furthermore, some or all of the above-described embodiments can be described as, but are not limited to, the following supplementary notes. (Appendix 1) an acquisition means for acquiring a predetermined number or more of measured values ​​of communication quality information in an optical communication path; an estimation means for calculating an average value of the acquired measurement values, generating a first cumulative distribution function of the communication quality information based on the acquired measurement values, and estimating a second cumulative distribution function of the communication quality information based on the acquired measurement values ​​when more measurement values ​​than the number of acquired measurement values ​​are acquired, based on the average value and the first cumulative distribution function; a determination means for determining, as a reference quality value, a value of the communication quality information at which a cumulative probability becomes a predetermined value in the second cumulative distribution function. (Appendix 2) the estimation means calculates a slope in a region where the cumulative probability changes sharply in the first cumulative distribution function, and approximates the second cumulative distribution function in the region where the cumulative probability changes sharply to a straight line based on the average value and the slope; The communication device according to claim 1, wherein the determination means determines the reference quality value using the straight line. (Appendix 3) the estimation means, when a first parameter, which is a parameter in the optical communication path and on which a variance of a value of the communication quality information depends, is changed, calculates the slope after the first parameter is changed, and calculates the average value after the first parameter is changed; The communication device described in Appendix 2, wherein the determination means determines the reference quality value after the first parameter is changed based on the average value after the first parameter is changed and the slope after the first parameter is changed. (Appendix 4) 4. The communication device according to claim 3, wherein the first parameter includes at least one of a modulation scheme used in the optical communication path and a guard band of a communication channel of the optical communication path. (Appendix 5) when a second parameter, which is a parameter in the optical communication path and in which the variance of the value of the communication quality information does not depend on the value of the second parameter, is changed, the estimation means calculates a difference between the average value before the second parameter is changed and a first reference quality value indicating the reference quality value before the second parameter is changed as a margin value, and calculates a first average value indicating the average value after the second parameter is changed; The communication device according to any one of claims 1 to 4, wherein the determination means determines the reference quality value after the second parameter is changed based on the first average value and the margin value. (Appendix 6) The communication device according to claim 5, wherein the determination means determines a value obtained by subtracting the margin value from the first average value as the reference quality value after the second parameter is changed. (Appendix 7) the estimation means, when a second parameter is changed, the second parameter being a parameter in the optical communication path, the variance of the value of the communication quality information not depending on the value of the second parameter, calculates a difference between a first average value indicating the average value after the second parameter is changed and a second average value indicating the average value before the second parameter is changed; The communication device according to any one of appendices 1 to 6, wherein the determination means determines the reference quality value after the second parameter is changed based on a first reference quality value indicating the reference quality value before the second parameter is changed and the difference. (Appendix 8) The determining means is When the first average value is greater than the second average value, a value obtained by adding the difference to the first reference quality value is determined as the reference quality value after the second parameter is changed; A communication device as described in Appendix 7, wherein, when the first average value is smaller than the second average value, a value obtained by subtracting the difference from the first reference quality value is determined as the reference quality value after the second parameter is changed. (Appendix 9) 9. The communication device according to claim 5, wherein the second parameter includes at least one of an optical transmission output and a number of communication channels in the optical communication path. (Appendix 10) The communication device according to any one of appendixes 3 to 9, further comprising a control means for changing the parameter so that the reference quality value after the parameter is changed satisfies a required quality value. (Appendix 11) Acquire a predetermined number or more of measured values ​​of communication quality information in the optical communication path; calculating an average value of the acquired measurement values, generating a first cumulative distribution function of the communication quality information based on the acquired measurement values, and estimating a second cumulative distribution function of the communication quality information based on a measurement value when a number of measurement values ​​acquired is greater than the number of acquired measurement values, based on the average value and the first cumulative distribution function; a value of the communication quality information at which a cumulative probability becomes a predetermined value in the second cumulative distribution function is determined as a reference quality value. (Appendix 12) Acquire a predetermined number or more of measured values ​​of communication quality information in the optical communication path; calculating an average value of the acquired measurement values, generating a first cumulative distribution function of the communication quality information based on the acquired measurement values, and estimating a second cumulative distribution function of the communication quality information based on a measurement value when a number of measurement values ​​acquired is greater than the number of acquired measurement values, based on the average value and the first cumulative distribution function; A non-transitory computer-readable medium storing a program for causing a computer to execute a process of determining, as a reference quality value, a value of the communication quality information at which a cumulative probability becomes a predetermined value in the second cumulative distribution function. (Appendix 13) a first communication device and a second communication device connected to the first communication device via an optical communication path; The first communication device is Measure communication quality information in the optical communication path a predetermined number of times or more to obtain a predetermined number of measurement values ​​or more; The second communication device is calculating an average value of the acquired measurement values, generating a first cumulative distribution function of the communication quality information based on the acquired measurement values, and estimating a second cumulative distribution function of the communication quality information based on a measurement value when a number of measurement values ​​acquired is greater than the number of acquired measurement values, based on the average value and the first cumulative distribution function; a value of the communication quality information at which a cumulative probability becomes a predetermined value in the second cumulative distribution function is determined as a reference quality value. (Appendix 14) The second communication device is calculating a slope in a region where the cumulative probability changes sharply in the first cumulative distribution function, and approximating the second cumulative distribution function in the region where the cumulative probability changes sharply to a straight line based on the average value and the slope; 14. The optical communication system of claim 13, wherein the straight line is used to determine the reference quality value. [Explanation of symbols]

[0174] 1. Communications equipment 2, 22, 52 Acquisition part 3 Estimation part 4 Decision Section 10, 40 Terminal equipment 20, 30, 60, 70 Optical transmission equipment 21, 31, 51, 61, 71 Communications Department 23, 53 Cumulative distribution estimator 24, 54 Communication quality determination unit 25, 55 Control section 26, 56 storage section 32 Measurement section 50 Network monitoring equipment 100, 200 Optical communication system P1, P3 communication path P2 optical communication path

Claims

1. an acquisition means for acquiring a predetermined number or more of measured values ​​of communication quality information in an optical communication path; an estimation means for calculating an average value of the acquired measurement values, generating a first cumulative distribution function of the communication quality information based on the acquired measurement values, and estimating a second cumulative distribution function of the communication quality information based on the acquired measurement values ​​when a larger number of measurement values ​​than the number of acquired measurement values ​​is acquired, based on the average value and the first cumulative distribution function; a determination means for determining, as a reference quality value, a value of the communication quality information at which a cumulative probability becomes a predetermined value in the second cumulative distribution function.

2. the estimation means calculates a slope of the first cumulative distribution function in a region where the cumulative probability is within a predetermined range, and approximates the second cumulative distribution function in the region to a straight line based on the average value and the slope; The communication device according to claim 1 , wherein the determining means determines the reference quality value using the straight line.

3. the estimation means, when a first parameter, which is a parameter in the optical communication path and on which a variance of a value of the communication quality information depends, is changed, calculates the slope after the first parameter is changed, and calculates the average value after the first parameter is changed; 3. The communication device according to claim 2, wherein the determination means determines the reference quality value after the first parameter is changed based on the average value after the first parameter is changed and the slope after the first parameter is changed.

4. the estimation means, when a second parameter, which is a parameter in the optical communication path and in which the variance of the value of the communication quality information does not depend on the value of the second parameter, is changed, calculates a difference between the average value before the second parameter is changed and a first reference quality value indicating the reference quality value before the second parameter is changed as a margin value, and calculates a first average value indicating the average value after the second parameter is changed; The communication device according to claim 1 , wherein the determining means determines the reference quality value after the second parameter is changed based on the first average value and the margin value.

5. the estimation means, when a second parameter is changed, the second parameter being a parameter in the optical communication path, the variance of the value of the communication quality information not depending on the value of the second parameter, calculates a difference between a first average value indicating the average value after the second parameter is changed and a second average value indicating the average value before the second parameter is changed; The communication device according to any one of claims 1 to 3, wherein the determination means determines the reference quality value after the second parameter is changed based on a first reference quality value indicating the reference quality value before the second parameter is changed and the difference.

6. The determining means is When the first average value is greater than the second average value, a value obtained by adding the difference to the first reference quality value is determined as the reference quality value after the second parameter is changed; 6. The communication device according to claim 5, wherein, when the first average value is smaller than the second average value, a value obtained by subtracting the difference from the first reference quality value is determined as the reference quality value after the second parameter is changed.

7. 7. The communication device according to claim 3, further comprising a control means for changing the parameter so that the reference quality value after the parameter is changed satisfies a required quality value.

8. Acquire a predetermined number or more of measured values ​​of communication quality information in the optical communication path; calculating an average value of the acquired measurement values, generating a first cumulative distribution function of the communication quality information based on the acquired measurement values, and estimating a second cumulative distribution function of the communication quality information based on the acquired measurement values ​​when more measurement values ​​than the number of acquired measurement values ​​are acquired, based on the average value and the first cumulative distribution function; a value of the communication quality information at which a cumulative probability becomes a predetermined value in the second cumulative distribution function is determined as a reference quality value.

9. Acquire a predetermined number or more of measured values ​​of communication quality information in the optical communication path; calculating an average value of the acquired measurement values, generating a first cumulative distribution function of the communication quality information based on the acquired measurement values, and estimating a second cumulative distribution function of the communication quality information based on the acquired measurement values ​​when more measurement values ​​than the number of acquired measurement values ​​are acquired, based on the average value and the first cumulative distribution function; determining, as a reference quality value, a value of the communication quality information at which a cumulative probability becomes a predetermined value in the second cumulative distribution function; program.

10. a first communication device and a second communication device connected to the first communication device via an optical communication path; The first communication device is measuring communication quality information in the optical communication path a predetermined number of times or more to obtain a predetermined number of measurement values ​​or more; The second communication device is calculating an average value of the acquired measurement values, generating a first cumulative distribution function of the communication quality information based on the acquired measurement values, and estimating a second cumulative distribution function of the communication quality information based on the acquired measurement values ​​when more measurement values ​​than the number of acquired measurement values ​​are acquired, based on the average value and the first cumulative distribution function; a value of the communication quality information at which a cumulative probability becomes a predetermined value in the second cumulative distribution function is determined as a reference quality value.

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