Method and apparatus for preventive maintenance of optical modules

Abstract

This invention provides a preventive maintenance device and method for optical modules that accurately predicts the bit error rate (BER) according to the degradation status of the optical module and prompts the replacement of the optical module at the appropriate time. [Solution] The optical module 101 includes an internal measuring instrument 1 that measures physical quantities including optical transmission power 12 and bias current 11, and an internal memory 2 in which the measured physical quantities are recorded. The information device 103 includes a correlation coefficient calculator 3 that calculates a correlation coefficient 16 for converting the optical transmission power measurement value to signal quality 17 from the optical transmission power measurement value 12a and bias current measurement value 11a recorded in the internal memory, a signal quality calculator 4 that calculates the signal quality using a correlation formula including the optical transmission power measurement value and the correlation coefficient, and a signal quality degradation determination device 5 that compares the signal quality with a signal quality degradation specified value 18 to diagnose the degradation of the signal quality, and uses the results of the diagnosis in the signal quality degradation determination device to report the degradation information 19 of the light-emitting element of the optical module 101.

Description

Technical Field

[0001] The present invention relates to a preventive maintenance method for an optical module and a preventive maintenance device for an optical module.

Background Art

[0002] An optical module is a main component device in a data center. It is widely used as a standardized interface for connecting storage devices, storage network devices (switches), etc., and supports the backbone of a communication network.

[0003] Patent Document 1 discloses a control method for predicting the degree of deterioration of an optical module by assigning cumulative points according to the operating time, environmental temperature, optical transmission power, and bias current value of a semiconductor laser of the optical module.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the presence or absence of signal abnormalities in a communication network is often determined by the bit error rate (BER), which is an index of signal quality. Also, as a function of an optical module alone, it is difficult to measure the BER. Therefore, it has been difficult to clarify the influence of the degree of deterioration of an optical module on the BER.

[0006] When attempting to determine the degree of degradation of an optical module as a preventative maintenance procedure based on its operating time, ambient temperature, optical transmission power, and semiconductor laser bias current value, the BER (Beam Equivalent) is not taken into consideration. As a result, it is not possible to encourage the replacement of optical modules at an appropriate time considering the entire communication network, leading to the problem of increased replacement costs due to premature replacement of optical modules.

[0007] Patent Document 1 discloses a control method for predicting the degree of degradation of an optical module based on the cumulative points of operating time, ambient temperature, optical transmission power, and semiconductor laser bias current value. However, Patent Document 1 does not include any description that takes BER into consideration.

[0008] The present invention has been made in view of the above points, and aims to realize a preventive maintenance method and a preventive maintenance device for optical modules that can predict the BER with high accuracy according to the degradation status of the optical module and encourage the replacement of the optical module at an appropriate time.

[0009] Furthermore, the above-mentioned objectives and other objectives of the present invention, as well as the novel features of the present invention, will be made clearer by the description herein and the accompanying drawings. [Means for solving the problem]

[0010] The present invention provides a preventive maintenance method for optical modules that prevents and maintains the degradation of optical modules. Furthermore, the present invention provides a preventive maintenance method for an optical module, in which the optical module is equipped with an internal measuring instrument that measures physical quantities including optical transmission power and bias current, and an internal memory that records the measured physical quantities. The control unit includes a correlation coefficient calculator that calculates a correlation coefficient for converting optical transmission power to signal quality from the optical transmission power and bias current recorded in the internal memory of the optical module, a signal quality calculator that calculates signal quality using a correlation formula that includes optical transmission power and correlation coefficient, and a signal quality degradation determination device that compares the signal quality with a specified signal quality degradation value and diagnoses the degradation of signal quality. The control unit then uses the results of the diagnosis made by the signal quality degradation determination device to notify the degradation status of the light-emitting element of the optical module.

[0011] The optical module preventive maintenance device of the present invention is an optical module preventive maintenance device that prevents and maintains the deterioration of the optical module. Furthermore, the optical module preventive maintenance device of the present invention includes an internal measuring instrument that measures physical quantities including optical transmission power and bias current, an internal memory that records the measured physical quantities, a correlation coefficient calculator that calculates a correlation coefficient for converting optical transmission power to signal quality from the optical transmission power and bias current recorded in the internal memory of the optical module, a signal quality calculator that calculates the signal quality using a correlation formula that includes optical transmission power and correlation coefficient, and a signal quality degradation determination device that compares the signal quality with a specified signal quality degradation value to diagnose the degradation of signal quality, and uses the results of the diagnosis in the signal quality degradation determination device to notify the degradation status of the light-emitting element of the optical module. [Effects of the Invention]

[0012] According to the present invention described above, the BER can be predicted with high accuracy according to the degradation status of the optical module, and the replacement of the optical module at the appropriate time can be promoted.

[0013] Furthermore, issues, configurations, and effects other than those mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0014] [Figure 1] It is a configuration diagram of a preventive maintenance procedure for an optical module according to Example 1. [Figure 2] It is a schematic configuration diagram (block diagram) of the optical module in FIG. 1. [Figure 3] It is a flowchart of a preventive maintenance procedure for an optical module according to Example 1. [Figure 4] It is a diagram showing a method for calculating the correlation coefficient in the signal quality converter of FIGS. A and B. [Figure 5] It is a flowchart of a preventive maintenance procedure for an optical module according to Example 2.

Mode for Carrying Out the Invention

[0015] In the following embodiments, when necessary for convenience, they are divided and described in multiple sections or embodiments. However, unless otherwise explicitly stated, they are not unrelated to each other, and one is related to a partial or full modification example, details, supplementary explanation, etc. of the other.

[0016] Also, in the following embodiments, when referring to the number of elements, etc. (including the number, numerical value, quantity, range, etc.), unless otherwise explicitly stated or limited to a specific number in principle, it is not limited to that specific number, and it may be more than or less than the specific number. Furthermore, in the following embodiments, it is needless to say that the constituent elements (including element steps, etc.) are not necessarily essential unless otherwise explicitly stated or considered to be essential in principle. Similarly, in the following embodiments, when referring to the shape, positional relationship, etc. of the constituent elements, unless otherwise explicitly stated or considered not to be so in principle, it includes those substantially approximating or similar to the shape, etc. This also applies to the above numerical values and ranges.

[0017] Also, in all the figures for explaining the following embodiments, those having the same function are generally given the same reference numerals, and the repeated description thereof is omitted.

[0018] The preventive maintenance method of the optical module of the present invention is a preventive maintenance method for preventing and maintaining the deterioration of the optical module. In the preventive maintenance method of the optical module of the present invention, the optical module includes an internal measuring instrument that measures physical quantities including optical transmission power and bias current, and an internal memory in which the measured physical quantities are recorded. Then, the preventive maintenance method of the optical module of the present invention uses a control unit having a correlation coefficient calculator that calculates a correlation coefficient for converting optical transmission power into signal quality from the optical transmission power and bias current recorded in the internal memory of the optical module, a signal quality calculator that calculates signal quality using a correlation formula including optical transmission power and the correlation coefficient, and a signal quality deterioration determination unit that compares the signal quality with a signal quality deterioration specified value and diagnoses the deterioration of the signal quality, and uses the result of the diagnosis in the signal quality deterioration determination unit to notify the deterioration status of the light emitting element of the optical module.

[0019] The preventive maintenance device of the optical module of the present invention is a preventive maintenance device for preventing and maintaining the deterioration of the optical module. The preventive maintenance device of the optical module of the present invention targets an optical module including an internal measuring instrument that measures physical quantities including optical transmission power and bias current, and an internal memory in which the measured physical quantities are recorded. Then, the preventive maintenance device of the optical module of the present invention has a correlation coefficient calculator that calculates a correlation coefficient for converting optical transmission power into signal quality from the optical transmission power and bias current recorded in the internal memory of the optical module, a signal quality calculator that calculates signal quality using a correlation formula including optical transmission power and the correlation coefficient, and a signal quality deterioration determination unit that compares the signal quality with a signal quality deterioration specified value and diagnoses the deterioration of the signal quality, and uses the result of the diagnosis in the signal quality deterioration determination unit to notify the deterioration status of the light emitting element of the optical module.

[0020] The above-described preventive maintenance method for an optical module and the preventive maintenance apparatus for an optical module of the present invention apply to an optical module equipped with an internal measuring instrument that measures physical quantities including optical transmission power and bias current, and an internal memory that records the measured physical quantities. Optical modules with this configuration are installed, for example, in storage devices and storage network equipment in data centers, as mentioned above, and are connected to the devices and equipment via a wired interface. Furthermore, as shown in the embodiment described later, the optical module can be configured to measure physical quantities other than optical transmission power and bias current (optical reception power, module ambient temperature, module power supply voltage, etc.) and record the measured physical quantities in its internal memory.

[0021] The optical module preventive maintenance method and optical module preventive maintenance apparatus of the present invention use a control unit or control device that includes at least a correlation coefficient calculator, a signal quality calculator, and a signal quality degradation determination device. The correlation coefficient calculator calculates a correlation coefficient for converting optical transmission power into signal quality from the optical transmission power and bias current recorded in the internal memory of the optical module. The signal quality calculator calculates the signal quality using a correlation formula that includes the optical transmission power and the correlation coefficient calculated by the correlation coefficient calculator. The signal quality degradation detector compares the signal quality with a specified signal quality degradation value to diagnose signal quality degradation. Furthermore, in the optical module preventive maintenance method and optical module preventive maintenance apparatus of the present invention, the results of the diagnosis in this signal quality degradation determination device are used to notify the degradation status of the light-emitting element of the optical module.

[0022] In the optical module preventive maintenance method and optical module preventive maintenance apparatus of the present invention, the control unit and control unit can be configured with various hardware processors such as a CPU (Central Processing Unit). Furthermore, this CPU or other hardware processor can be, for example, a hardware processor built into a storage device or storage network device to which an optical module is connected.

[0023] According to the optical module preventive maintenance method and optical module preventive maintenance device of the present invention, signal quality is calculated using a correlation formula that includes optical transmission power and a correlation coefficient, the signal quality is compared with a specified signal quality degradation value, the degradation of signal quality is diagnosed, and the degradation status of the light-emitting element of the optical module is reported using the results of the diagnosis. This allows for highly accurate prediction of the BER based on the degradation status of the optical module, enabling timely replacement of the optical module. [Examples]

[0024] Next, specific embodiments of the present invention will be described in detail with reference to the drawings.

[0025] (Example 1) The preventive maintenance procedure for the optical module according to Embodiment 1 of the present invention will be described below with reference to Figures 1 to 4.

[0026] Figure 1 is a diagram illustrating the configuration of the preventive maintenance procedure for the optical module according to Example 1. The preventive maintenance procedure for the optical module in this embodiment comprises an optical module 101 and an information device 103 connected to the optical module 101.

[0027] Information device 103 is an information device to which the optical module 101 is connected, and examples include storage devices and network switches used in data centers. In data centers, the numerous storage devices are often connected to each other and to network switches using multimode fiber (MMF). Furthermore, the storage devices and network switches are connected to the multimode fiber using optical modules 101.

[0028] The optical module 101 includes an internal measuring instrument 1 and an internal memory 2. The optical module 101 then measures the bias current 11, optical transmission power 12, optical reception power 13, module ambient temperature 14, and module power supply voltage 15 using an internal measuring instrument 1, and stores the results of these measurements in the internal memory 2.

[0029] The information device 103 includes a signal quality converter 102 and a signal quality degradation detector 5. Furthermore, the signal quality converter 102 includes a correlation coefficient calculator 3 and a signal quality calculator 4.

[0030] The information device 103 operates as described below. First, the information device 103 reads out the bias current measurement value 11a and the optical transmission power measurement value 12a stored in the internal memory 2. Then, the correlation coefficient calculator 3 in the signal quality converter 102 uses the read bias current measurement value 11a and the optical transmission power measurement value 12a to calculate a correlation coefficient 16 for converting optical transmission power into signal quality. Next, the signal quality calculator 4 calculates the signal quality 17 from the correlation coefficient 16 and the optical transmission power measurement value 12a. Next, the signal quality degradation detector 5 compares the signal quality 17 with a preset signal quality degradation value 18. If the signal quality 17 is worse than the signal quality degradation value 18, the signal quality degradation detector 5 notifies the light-emitting element degradation information 19.

[0031] The internal measuring instrument 1 and internal memory 2 of the optical module 101 may be replaced with the DDM (Digital Diagnostic Monitoring) function, which is supported as a standard feature of general optical modules. The bias current measurement value 11a and the optical transmission power measurement value 12a may be values ​​measured using measuring instruments such as an ammeter or optical power meter. Signal quality 17 can be measured using TDECQ (Transmitter and Dispersion penalty Eye Closure for PAM4) instead of BER.

[0032] Figure 2 is a schematic configuration diagram (block diagram) of the optical module 101 in Figure 1, relating to Example 1. Note that the block diagram in Figure 2 shows a general configuration of the optical module and can be applied in both cases, whether or not the DDM function is adopted. Figure 2 shows the optical module 101 and the connected devices 20 connected to the optical module 101. The connected devices 20 also include the information equipment 103 (storage device, network switch, etc.) shown in Figure 1. As shown in Figure 2, the printed circuit board 21 inside the housing (case) of the optical module 101 is equipped with a CDR22, LD23, temperature sensor 24, transmitting optical element 25, receiving optical element 26, TIA27, CDR28, and MCU29. CDR (Clock and Data Recovery) 22,28 receive signals on a transmission path in which a clock signal is superimposed on the data, and separate the clock from the data. The LD (Laser Driver) 23 causes a light-emitting element such as a laser to oscillate. The temperature sensor 24 detects the ambient temperature. The transmitting optical element 25 is a light-emitting element that is a laser such as a VCSEL (Vertical Cavity Surface Emitting Laser). The receiving optical element 26 is a light-receiving element such as a photodiode. The TIA (Trance Impedance Amplifier) ​​27 is an amplifier that converts an input current into a voltage that is twice the resistance (impedance). The MCU (microcontroller unit) 29 controls the CDR 22, LD 23, temperature sensor 24, transmitting optical element 25, receiving optical element 26, TIA 27, and CDR 28.

[0033] MCU29 is I 2Signals are exchanged between the connected device 20 and the device via C communication. The data transmitted from the connected device 20 flows from the connected device 20 to the CDR 22, LD 23, and the transmitting optical element 25. The flow of received data to the connected device 20 is from the receiving optical element 26 to the TIA 27, CDR 28, and then to the connected device 20. By exchanging data and control signals in this manner, the optical module 101 can store various measured values ​​11 to 15 in its built-in memory 2, as shown in Figure 1.

[0034] Figure 3 is a flowchart of the preventive maintenance procedure for the optical module according to Example 1.

[0035] In this embodiment, as shown in Figure 3, first, the user sets an arbitrary signal quality degradation value 18 and inputs the set signal quality degradation value 18 (step S200). Next, the information device 103 obtains the bias current measurement value 11a and the optical transmission power measurement value 12a from the internal memory 2 of the optical module 101 (step S201). Next, the correlation coefficient calculator 3 in the signal quality converter 102 of the information device 103 calculates the correlation coefficient 16 from the bias current measurement value 11a and the optical transmission power measurement value 12a (step S202). Next, the signal quality calculator 4 calculates the signal quality 17 from the optical transmission power measurement value 12a and the correlation coefficient 16 (step S203).

[0036] Next, the signal quality degradation determination device 5 compares the signal quality 17 with the signal quality degradation specified value 18 and determines whether the signal quality 17 has deteriorated beyond the signal quality degradation specified value 18 (step S204).

[0037] If "No" (no deterioration) is determined in step S204, the system waits for an arbitrary amount of time (step S205), and the signal quality converter 102 obtains the updated optical transmission power measurement value 12a (step S207). Then, the signal quality calculator 4 calculates the signal quality 17 from the correlation coefficient 16 calculated in step S202 and the updated optical transmission power measurement value 12a (step S208). Then, step S204 is executed again.

[0038] If "Yes" (deterioration) is determined in step S204, the signal quality degradation detector 5 reports the light-emitting element degradation information 19 (step S206).

[0039] Here, we will explain in detail the functions of the signal quality converter 102. First, the signal quality converter 102 defines a correlation formula for converting the optical transmission power measurement value 12a into a signal quality 17. The correlation formula is expressed by the following equation (1.1).

[0040]

number

[0041] The first feature, A, is calculated from the relationship between A and the ratio of optical transmission power to bias current, representing the value of A when the ratio is a specific value. The second feature, B, is calculated from the relationship between B and the ratio of optical transmission power to bias current, representing the value of B when the ratio is a specific value.

[0042] The first feature A and the second feature B are determined for each optical module 101 by dividing the optical transmission power measurement value 12a by the bias current measurement value 11a (IL slope S I-L Based on this, the following equations (2) and (3) can be defined. A = α¹ × S I-L β1 (2) B = α² × S I-L β2 (3) In the above equation, α1, β1, α2, and β2 are fitting parameters, and their respective domains are α1>0, β1<0, α2<0, and β2<0. The values ​​of these fitting parameters α1, β1, α2, and β2 can be appropriately defined within the range of their domains, corresponding to the characteristics of the optical module 101.

[0043] Figures 4A and 4B illustrate the calculation method for the correlation coefficient in the signal quality converter 102 of Figure 1, and represent the calculation methods for the first feature A and the second feature B, respectively. The horizontal axis in Figures 4A and 4B represents the IL slope (the value obtained by dividing the optical transmission power measurement value 12a by the bias current measurement value 11a), and the vertical axis in Figures 4A and 4B represents the first feature A and the second feature B, respectively. The dashed lines in Figures 4A and 4B represent the correlation between the first feature A, the second feature B, and the IL slope, as determined by equations (2) and (3) above.

[0044] Then, as shown by the solid lines in Figures 4A and 4B, the value of the IL slope becomes a specific value depending on the state of the optical module 101, and the values ​​of the first feature A and the second feature B are determined from this specific value of the IL slope and the correlation characteristics shown by the dashed line. Furthermore, the TDECQ of the signal quality 17 can be determined based on the established first feature A, second feature B, and optical transmission power measurement value 12a.

[0045] Furthermore, since TDECQ can be converted to BER as shown in equation (1.2) below, it is also possible to replace signal quality 17 with BER.

[0046]

number

[0047] As described above, the preventive maintenance procedure for the optical module according to this embodiment can accurately predict the BER according to the degradation status of the optical module and prompt the replacement of the optical module at the appropriate time.

[0048] (Example 2) The following describes the preventive maintenance procedure for an optical module according to Embodiment 2 of the present invention. Figure 5 is a flowchart of the preventive maintenance procedure for an optical module according to Embodiment 2 of the present invention.

[0049] The difference between the preventive maintenance procedure for the optical module in this embodiment and the preventive maintenance procedure for the optical module in Embodiment 1 is that the correlation coefficient calculator 3 in the signal quality converter 102 of the information device 103 calculates the correlation coefficient 16 at arbitrary time intervals.

[0050] In this embodiment, as shown in Figure 5, first, the user sets an arbitrary signal quality degradation value 18 and inputs the set signal quality degradation value 18 (step S400). Next, the information device 103 obtains the bias current measurement value 11a and the optical transmission power measurement value 12a from the internal memory 2 of the optical module 101 (step S401). Next, the correlation coefficient calculator 3 in the signal quality converter 102 of the information device 103 calculates the correlation coefficient 16 from the bias current measurement value 11a and the optical transmission power measurement value 12a (step S402). Next, the signal quality calculator 4 calculates the signal quality 17 from the optical transmission power measurement value 12a and the correlation coefficient 16 (step S403).

[0051] Next, the signal quality degradation determination device 5 compares the signal quality 17 with the signal quality degradation specified value 18 and determines whether the signal quality 17 has deteriorated beyond the signal quality degradation specified value 18 (step S404).

[0052] If "No" (not worsened) is determined in step S404, the system waits for an arbitrary amount of time (step S405), and the signal quality converter 102 acquires the updated bias current measurement value 11a and optical transmission power measurement value 12a (step S407). Then, the correlation coefficient calculator 3 calculates the correlation coefficient 16 from the updated bias current measurement value 11a and optical transmission power measurement value 12a (step S408). Next, the signal quality calculator 4 calculates the signal quality 17 from the updated optical transmission power measurement value 11a and the correlation coefficient 16 (step S409). Then, step S404 is executed again.

[0053] If "Yes" (deterioration) is determined in step S404, the signal quality degradation detector 5 notifies the light-emitting element degradation information 19 (step S406).

[0054] As described above, the optical module preventive maintenance procedure according to this embodiment can predict the BER with high accuracy according to the degradation status of the optical module and encourage the replacement of the optical module at the appropriate time.

[0055] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are explained in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace a part of the configuration example of one embodiment with another configuration example of the same embodiment or another configuration example of a different embodiment, and it is also possible to add the configurations of another configuration example of the same embodiment or another configuration example to a configuration example of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0056] Furthermore, each of the above configurations, functions, processing units, and processing means may be implemented in hardware, either partially or entirely, by designing them as integrated circuits, for example. Alternatively, each of the above configurations and functions may be implemented in software by having the processor interpret and execute programs that implement each function. Information such as programs, tables, and files that implement each function can be stored in memory, a recording device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD.

[0057] Furthermore, the control lines and information lines shown are those deemed necessary for explanatory purposes, and not all control lines and information lines are necessarily shown in the actual product. In reality, it is safe to assume that almost all components are interconnected. [Explanation of Symbols]

[0058] 1 Internal measuring instrument, 2 Internal memory, 3 Correlation coefficient calculator, 4 Signal quality calculator, 5 Signal quality degradation detector, 20 Connecting equipment, 21 Printed circuit board, 22, 28 CDR, 23 LD, 24 Temperature sensor, 25 Transmitting optical element, 26 Receiving optical element, 27 TIA, 29 MCU, 101 Optical module, 102 Signal quality converter, 103 Information equipment

Claims

1. A preventive maintenance method for optical modules, which prevents and preserves the degradation of optical modules, The optical module includes an internal measuring instrument for measuring physical quantities including optical transmission power and bias current, and an internal memory for recording the measured physical quantities. Using a control unit comprising: a correlation coefficient calculator that calculates a correlation coefficient for converting the optical transmission power to signal quality from the optical transmission power and the bias current recorded in the internal memory of the optical module; a signal quality calculator that calculates the signal quality using a correlation formula including the optical transmission power and the correlation coefficient; and a signal quality degradation determination device that compares the signal quality with a specified signal quality degradation value and diagnoses the degradation of signal quality, The results of the diagnosis by the signal quality degradation determination device are used to report the degradation status of the light-emitting element of the optical module. Preventive maintenance methods for optical modules.

2. The correlation coefficient calculator calculates the correlation coefficient using the correlation formula shown in the following equation (1.1). The method for preventive maintenance of an optical module according to claim 1. [In equation (1.1), TDECQ is the signal quality, and P Tx [A is the measured value of the optical transmission power, and B are the first and second feature quantities obtained from the measured value of the bias current and the measured value of the optical transmission power.]

3. The first feature, A, is calculated as the value of A when the ratio of optical transmission power to bias current is a specific value, based on the relationship of A to the ratio of optical transmission power to bias current. The second feature, B, is calculated as the value of B when the ratio of B to optical transmission power to bias current is a specific value, based on the relationship of B to the ratio of optical transmission power to bias current. The method for preventive maintenance of an optical module according to claim 2.

4. The relationship A with respect to the ratio of optical transmission power to bias current is expressed by the following equation (2), and the relationship B with respect to the ratio of optical transmission power to bias current is expressed by the following equation (3). The method for preventive maintenance of an optical module according to claim 3. A=α1×S Ｉ－Ｌ β１ (2) B=α2×S Ｉ－Ｌ β２ (3) [In equations (2) and (3), α1, β1, α2, and β2 are fitting parameters, and their respective domains are α1 > 0, β1 < 0, α2 < 0, and β2 < 0.]

5. In the correlation coefficient calculator, the correlation coefficient is updated at arbitrary time intervals. The method for preventive maintenance of an optical module according to claim 1.

6. A preventive maintenance device for optical modules that prevents and maintains the degradation of optical modules, The optical module includes an internal measuring instrument for measuring physical quantities including optical transmission power and bias current, and an internal memory for recording the measured physical quantities, A correlation coefficient calculator that calculates a correlation coefficient for converting the optical transmission power into signal quality from the optical transmission power and the bias current recorded in the internal memory of the optical module, A signal quality calculator that calculates signal quality using a correlation formula that includes the optical transmission power and the correlation coefficient, The system includes a signal quality degradation determination device that compares the aforementioned signal quality with a specified signal quality degradation value to diagnose signal quality degradation, The results of the diagnosis by the signal quality degradation determination device are used to report the degradation status of the light-emitting element of the optical module. A preventative maintenance device for optical modules.

7. The predictive maintenance device for an optical module according to claim 6, wherein the correlation coefficient calculator updates the correlation coefficient at arbitrary time intervals.

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