JP3606235B2 - Semiconductor laser degradation monitoring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor laser deterioration monitoring device that monitors the deterioration of a semiconductor laser.
[0002]
[Prior art]
With the spread of communication networks such as the Internet and an increase in the amount of transmitted data, there is an increasing demand for an increase in transmission capacity of the transmission path. Under such a background, a WDM (wavelength division multiplex) optical transmission system has attracted attention. In this system, in order to increase the transmission capacity, the number of multiplexed wavelengths is increasing to 160 waves or more. Along with this, the wavelength interval is also narrowed, and therefore semiconductor lasers are required to have long-term wavelength stability.
[0003]
Therefore, a technique has been proposed in which a monitor voltage proportional to the drive current of the semiconductor laser is detected, and deterioration is determined when this voltage exceeds a reference voltage.
[0004]
[Problems to be solved by the invention]
However, in such a conventional semiconductor laser deterioration monitoring apparatus, the deterioration cannot be determined unless the semiconductor laser deterioration has progressed to some extent. In order to perform replacement immediately when a deterioration warning is issued, replacement semiconductor lasers must always be prepared for each wavelength. This requires a lot of backups and is very uneconomical.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor laser deterioration monitoring device that can grasp the progress of deterioration of individual semiconductor lasers and predict the lifetime, and aims to operate the WDM transmission apparatus economically.
[0006]
[Means for Solving the Problems]
According to the first aspect of the present invention, (a) a constant temperature control circuit for controlling the temperature of the semiconductor laser to a set temperature, (b) time measuring means for measuring a usage time from the start of use of the semiconductor laser, and (c) A characteristic for determining whether or not a predetermined characteristic predetermined for the semiconductor laser is different from the target value when a new set temperature is given and the temperature control circuit reaches the new set temperature by the temperature control circuit. Non-coincidence determining means, (d) error calculating means for obtaining an error from the target value when it is determined that the characteristic mismatch determining means does not match the target value, and (e) from the start of use of the semiconductor laser. History data creating means for creating history data in which the accumulated value of errors by the error calculating means and the corresponding usage time of the semiconductor laser are respectively paired; The semiconductor laser deterioration monitoring device includes a usage time determination means for determining a usage time until the above-described predetermined characteristics of the semiconductor laser reach a deterioration value indicating the deterioration of the semiconductor laser using the respective history data created in Provide.
[0007]
That is, according to the first aspect of the present invention, when a new set temperature is given to the temperature constant control circuit for controlling the temperature of the semiconductor laser to the set temperature, the temperature of the semiconductor laser is controlled to this set temperature based on this. The characteristic mismatch determining means determines whether or not a predetermined characteristic predetermined for the semiconductor laser is different from a target value when the semiconductor laser reaches the set temperature. For example, it is determined whether or not the wavelength output from the semiconductor laser matches the target value. When it is determined that it does not match the target value, an error with the target value is obtained by the error calculating means, and the accumulated value of the error by the error calculating means from the start of use of the semiconductor laser by the history data generating means and the corresponding value. History data in which the usage times of the semiconductor lasers are paired is created. That is, each time the characteristic mismatch determination means determines that the target value does not match, history data is added. The usage time determination means determines the usage time until the predetermined characteristic of the semiconductor laser reaches a degradation value indicating the degradation of the semiconductor laser, using each history data created by the history data creation means. Become.
[0008]
Thus, according to the first aspect of the present invention, since the state of deterioration of the semiconductor laser can be grasped by using each history data created by the history data creating means, it is determined when the semiconductor laser should be replaced. Can be exchanged efficiently and economically.
[0009]
In the invention described in claim 2, (a) a constant temperature control circuit for controlling the temperature of the semiconductor laser to a set temperature, (b) a time measuring means for measuring the usage time from the start of use of the semiconductor laser, and (c) When a new set temperature is applied and the temperature control circuit causes the semiconductor laser to reach the new set temperature, a predetermined characteristic predetermined for the semiconductor laser is different from the target value when the set temperature is reached. (D) an error calculation means for determining an error from the target value when the characteristic mismatch determination means determines that the target value does not match the target value; ) History data creation means for creating history data in which the accumulated value of the error by the error calculation means from the start of use of the semiconductor laser and the corresponding use time of the semiconductor laser are paired; F) The semiconductor laser deterioration monitoring device is provided with a graph display means for displaying each history data created by the history data creating means on a graph with the error and the usage time in the predetermined characteristics as coordinate axes. .
[0010]
That is, according to the second aspect of the present invention, a new set temperature is given to the constant temperature control circuit that controls the temperature of the semiconductor laser to the set temperature, and when the temperature of the semiconductor laser is controlled to the set temperature based on the set temperature. The characteristic mismatch determining means determines whether or not a predetermined characteristic predetermined for the semiconductor laser is different from a target value when the semiconductor laser reaches the set temperature. For example, it is determined whether or not the wavelength output from the semiconductor laser matches the target value. When it is determined that it does not match the target value, an error with the target value is obtained by the error calculating means, and the accumulated value of the error by the error calculating means from the start of use of the semiconductor laser by the history data generating means and the corresponding value. History data in which the usage times of the semiconductor lasers are paired is created. That is, each time the characteristic mismatch determination means determines that the target value does not match, history data is added. The graph display means displays each history data created by the history data creation means as a graph with the error and the usage time in the predetermined characteristics as coordinate axes.
[0011]
Thus, in the invention described in claim 2, since the state of deterioration of the semiconductor laser is displayed on the graph using the respective history data created by the history data creating means, it is possible to visually grasp the progress of the degradation. it can. Therefore, it is possible to determine when the semiconductor laser should be replaced, and efficient or economical replacement becomes possible.
[0012]
According to a third aspect of the present invention, (a) an injection current control circuit for controlling the injection current for the semiconductor laser to a predetermined set injection current value, and (b) a time measuring means for measuring the use time from the start of use of the semiconductor laser. (C) when a new set injection current value is given and the injection current constant control circuit reaches the new set injection current value, a predetermined characteristic predetermined for the semiconductor laser is set to this setting. Characteristic mismatch determination means for determining whether or not the target value is different from the target value when the temperature is reached, and (d) an error from the target value when it is determined that the characteristic mismatch determination means does not match the target value. (E) history data in which the accumulated value of error by the error calculation means from the start of use of the semiconductor laser and the corresponding use time of the semiconductor laser are respectively paired. (F) using the history data created by the history data creating means until the predetermined characteristics of the semiconductor laser reach a degradation value indicating degradation of the semiconductor laser. The semiconductor laser deterioration monitoring device is provided with a usage time determination means for determining the usage time.
[0013]
That is, in the third aspect of the invention, a new set injection current value is given to the injection current control circuit that controls the injection current to the semiconductor laser (different from the driving current of the semiconductor laser) to a predetermined set injection current value. When the injection current of the semiconductor laser is controlled to the set injection current value based on the above, is a predetermined characteristic predetermined for this semiconductor laser different from a target value determined for each semiconductor laser? Whether or not it is determined by the characteristic mismatch determination means. For example, it is determined whether or not the wavelength output from the semiconductor laser matches the target value. When it is determined that it does not match the target value, an error with the target value is obtained by the error calculating means, and the accumulated value of the error by the error calculating means from the start of use of the semiconductor laser by the history data generating means and the corresponding value. History data in which the usage times of the semiconductor lasers are paired is created. That is, each time the characteristic mismatch determination means determines that the target value does not match, history data is added. The usage time determination means determines the usage time until the predetermined characteristic of the semiconductor laser reaches a degradation value indicating the degradation of the semiconductor laser, using each history data created by the history data creation means. Become.
[0014]
In this way, in the invention described in claim 3, since it is possible to grasp the state of deterioration of the semiconductor laser using each history data created by the history data creating means, it is determined when the semiconductor laser should be replaced. Can be exchanged efficiently and economically.
[0015]
In the invention described in claim 4, (a) an injection current control circuit for controlling an injection current for the semiconductor laser to a predetermined set injection current value, and (b) a time measuring means for measuring a use time from the start of use of the semiconductor laser. (C) When a new set injection current value is given and the injection current constant control circuit causes the semiconductor laser to reach the new set injection current value, predetermined characteristics predetermined for the semiconductor laser are Characteristic mismatch determining means for determining whether or not the target value is different from the target value determined for the semiconductor laser; and (d) when it is determined that the characteristic mismatch determining means does not match the target value, An error calculation means for obtaining an error, and (e) a cumulative value of error by the error calculation means from the start of use of the semiconductor laser and a corresponding use time of the semiconductor laser, respectively. History data creation means for creating data, and (f) a graph display for displaying each history data created by the history data creation means on a graph with the error and the usage time in the predetermined characteristics as coordinate axes. A semiconductor laser deterioration monitoring device.
[0016]
That is, in the invention described in claim 4, a new set injection current value is given to the injection current control circuit for controlling the injection current to the semiconductor laser to a predetermined set injection current value, and the injection current of the semiconductor laser is based on this. When controlled to the set injection current value, the characteristic mismatch determination means determines whether or not a predetermined characteristic predetermined for the semiconductor laser is different from a target value determined for each semiconductor laser. I have to. For example, it is determined whether or not the wavelength output from the semiconductor laser matches the target value. When it is determined that it does not match the target value, an error with the target value is obtained by the error calculating means, and the accumulated value of the error by the error calculating means from the start of use of the semiconductor laser by the history data generating means and the corresponding value. History data in which the usage times of the semiconductor lasers are paired is created. That is, each time the characteristic mismatch determination means determines that the target value does not match, history data is added. The graph display means displays each history data created by the history data creation means as a graph with the error and the usage time in the predetermined characteristics as coordinate axes.
[0017]
Thus, in the invention described in claim 4, since the state of deterioration of the semiconductor laser is displayed in a graph using each history data created by the history data creating means, it is possible to visually grasp the progress of the degradation. it can. Therefore, it is possible to determine when the semiconductor laser should be replaced, and efficient or economical replacement becomes possible.
[0018]
According to a fifth aspect of the present invention, in the semiconductor laser deterioration monitoring device according to the second or fourth aspect, the graph display means displays a curve passing through the coordinate point indicating each history data, and the curve is a semiconductor. It is characterized in that the usage time to reach a degradation value indicating degradation with a predetermined characteristic of the laser is also displayed.
[0019]
That is, in the invention according to claim 5, the semiconductor laser deterioration monitoring apparatus according to claim 2 or 4 displays a curve passing through the coordinate point indicating the history data when the graph is displayed, and the future deterioration The state of is predicted and displayed. At this time, if the time corresponding to the point at which this curve reaches the deterioration value indicating the deterioration with the predetermined characteristics of the semiconductor laser is indicated, this is indicated as the use time until then.
[0020]
According to a sixth aspect of the present invention, in the semiconductor laser deterioration monitoring apparatus according to any one of the first to fourth aspects, the predetermined characteristic is a wavelength output from the semiconductor laser, and an error calculated by the error calculating means is It is characterized by a wavelength error from the target value.
[0021]
According to a seventh aspect of the invention, in the semiconductor laser deterioration monitoring device according to any one of the first to fourth aspects, the semiconductor laser deterioration monitoring device further comprises means for sequentially monitoring the deterioration of a plurality of semiconductor lasers with different processing times. Yes.
[0022]
That is, in the invention described in claim 7, when a plurality of semiconductor lasers are used as in the case of performing wavelength division multiplex transmission, it is necessary to prepare a replacement package more than necessary by monitoring the progress of these deteriorations. Not economical.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
[0026]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples.
[0027]
<First embodiment>
[0028]
FIG. 1 shows the configuration of a semiconductor laser deterioration monitoring apparatus according to the first embodiment of the present invention. The semiconductor laser (LD) 101 of the semiconductor laser deterioration monitoring apparatus 100 adjusts the temperature by a Peltier element (PE) 102. For this purpose, the thermistor (TH) 103 detects the temperature of the semiconductor laser 101. Yes. That is, the temperature control circuit unit (ATC) 104 controls the Peltier element 102 based on the temperature data 105 obtained from the thermistor 103, thereby heating or cooling the semiconductor laser 101 and holding it at a desired temperature. . The constant power control circuit (APC) 106 receives the monitor light 107 and supplies a drive signal 111 for controlling the power of the laser light transmitted to the transmission path 109 via the optical fiber 108 to the semiconductor laser 101. It has become.
[0029]
The semiconductor laser deterioration monitoring apparatus 100 is equipped with a DSP (digital signal processor) 112 for calculating the wavelength shift of the laser beam output from the semiconductor laser 101. The DSP 112 uses a program stored in a storage medium such as a ROM (Read Only Memory) (not shown) to temporarily store processing data in a working memory such as a RAM (Random Access Memory) not shown. In this way, data is input / output to / from each part of the apparatus.
[0030]
The wavelength locker 114 receives the signal light obtained by branching a part of the laser light directed to the transmission path 109 by the optical coupler 115, and supplies error data 117 representing the error Δλ to the target wavelength λ to the DSP 112. It comes to input. Temperature data 105 is input from the thermistor 103 to the DSP 112. Also, current data 118 representing the driving current I of the semiconductor laser 101 is input from the constant power control circuit 106 to the DSP 112. The DSP 112 is connected to a server 122 and sends data 123 for analysis to this. The DSP 112 sends set temperature data 124 for controlling the wavelength to the constant temperature control circuit unit 104.
[0031]
FIG. 2 shows the operation of the DSP. When the power of the semiconductor laser degradation monitoring apparatus 100 is turned on, the DSP 112 starts its control operation, and first, the monitor temperature T of the thermistor 103 (FIG. 1). _mon Is the set temperature T for the semiconductor laser 101 _set Is checked (step S141). Monitor temperature T _mon Is set temperature T _set Is not equal to (N), the temperature control circuit unit 104 waits for them to be equalized by controlling the temperature.
[0032]
In this way, the monitor temperature T _mon Is set temperature T _set (Step S141: Y), the DSP 112 inputs various information from the wavelength locker 114 or the like (step S142). Then, using the error data 117 output from the wavelength locker 114, the target wavelength λ _A And the error Δλ of the actually monitored wavelength λ _mon Whether or not is zero is determined (step S143). These relationships are as shown in the following equation (1).
Δλ _mon = Λ-λ _A ...... (1)
[0033]
The wavelength λ that is actually monitored is the target wavelength λ _A (Step S143: Y), the process returns to step S141 to continue the process (return). On the other hand, the actually monitored wavelength λ is the target wavelength λ. _A I.e., the error Δλ _mon Is not zero (N), the set temperature T to which the temperature ΔT shown in the following equation (2) is added so that it is zero _set Is calculated (step S144).
[0034]
T _set = T _ini + ΔT (2)
[0035]
T _ini Is the initial temperature T of the semiconductor laser 101 _ini It is. This initial value T _ini Is determined by viewing the wavelength output from the semiconductor laser 101 (FIG. 1) with a wavelength meter (not shown) at the time of initial setting, and is input to the DSP 112 from a keyboard or operation panel (not shown). In this embodiment, the DSP 112 is used, but other external circuits may be used.
[0036]
The DSP 112 calculates the set temperature T calculated by the equation (2). _set Is sent to the temperature control circuit unit 104 as set temperature data 124 (step S145). The elapsed time t from the start of use of the semiconductor laser 101 and the error Δλ _mon Etc. are sent to the server 122 (step S146), and the process returns to step S141 again (return).
[0037]
If the server 122 manages the elapsed time t from the start of use of the semiconductor laser 101 and knows the time, it is not necessary to transmit it to the server 122.
[0038]
As described above, in the semiconductor laser deterioration monitoring apparatus 100, the temperature of the semiconductor laser 101 is set to the set temperature T. _set Is obtained at the first time, and various information such as the drive current I is acquired, and the monitored wavelength λ is the target wavelength λ. _A In the state, control by the constant temperature control circuit unit 104 or the like is continued. Then, the wavelength λ monitored by the secular change of the semiconductor laser 101 is the target wavelength λ. _A If the difference between the two values exceeds a certain allowable value, a new set temperature T _set And the current predetermined data is transmitted to the server 122 in this state.
[0039]
For example, when the semiconductor laser 101 is a factory-shipped product (hereinafter referred to as a new product), the wavelength λ monitored in step S143 is the target wavelength λ. _A Depending on the product, it will usually take several years until it conflicts. In the meantime, the server 122 does not receive data from the DSP 112, and during this time it is dedicated to other tasks. Then, when the data shown in step S146 is sent from the DSP 112, control for predicting the lifetime of the corresponding semiconductor laser 101 is performed.
[0040]
FIG. 3 shows a processing flow on the server side when data is transmitted from the DSP. The server 122 shown in FIG. 1 monitors the arrival of predetermined data from the DSP 112 (step S161). When various data shown in step S146 of FIG. 2 are sent (Y), the elapsed time t and the error Δλ therein. _mon To extract. And the error Δλ _mon Is the cumulative λ from power-on _dev To determine the elapsed time t and the cumulative λ _dev Are sequentially stored in a predetermined storage area from the past (step S162).
[0041]
And the elapsed time t held until now and the cumulative λ _dev A graph is displayed based on the pair (step S163). In this graph, the elapsed time t expressed as each pair is represented on the x-axis, and the cumulative λ _dev Are expressed on the y-axis, and the elapsed time when the curve connecting these points becomes the limit value of the wavelength shift is predicted as the lifetime.
[0042]
FIG. 4 shows the elapsed time t displayed by the server and the cumulative λ _dev An example of the characteristic is shown. The server 122 shown in FIG. 1 acquires the elapsed time t and the cumulative λ every time data is acquired from the DSP 112. _dev Point d ₁ , D ₂ , D ₃ ,... Are created and stored in the storage area described above. And these points d ₁ , D ₂ , D ₃ ,... Is displayed as the lifetime when the curve 181 reaches the limit value of the wavelength shift on the x-axis.
[0043]
For example, it is assumed that the LD degradation determination threshold is when the wavelength of the semiconductor laser 101 shown in FIG. From FIG. 4, assuming that the year when the curve 181 is 0.1 nm on the x-axis is 20 years, the lifetime is 20 years. And the latest measurement point is point d ₄ If the elapsed time t at that time is 10 years, the remaining life t until then _remain Will be another 10 years.
[0044]
Of course, life or remaining life t _remain The point d obtained as reference data is ₁ , D ₂ , D ₃ The more you have, the more accurate it becomes. For example, the first point d ₁ It is possible to predict the life more accurately when more points d are obtained for the semiconductor laser 101 than the predicted value at the time of obtaining. The server 122 can request replacement of the semiconductor laser 101 when the lifetime has come, or at a point just before a predetermined time thereafter.
[0045]
<First Modification of First Embodiment>
[0046]
FIG. 5 shows the configuration of the semiconductor laser deterioration monitoring apparatus according to the first modification of the first embodiment of the present invention. In FIG. 5, the same parts as those in FIG. In the semiconductor laser degradation monitoring apparatus 100A of the first modification, a plurality of semiconductor lasers 101 that share each wavelength. ₁ , 101 ₂ , 101 ₃ , ... are arranged. These semiconductor lasers 101 ₁ , 101 ₂ , 101 ₃ ,... On the output side are optical fibers 108. ₁ , 108 ₂ , 108 ₃ ,... Are arranged, and the other ends thereof are connected to the input side of an optical multiplexer (OMUX) 331. The input side of the optical coupler 115 is connected to the output side of the optical multiplexer 331. The optical coupler 115 is the same as that of the previous embodiment, and the input optical signal is branched to the transmission path 109 and the wavelength locker 114 and output. Error data 117 representing an error Δλ with respect to the target wavelength λ output from the wavelength locker 114 is input to the DSP 112A and processed. Data 123A output from the DSP 112A is input to the server 122A to calculate the life.
[0047]
In FIG. 5, the Peltier element (PE) 102 and thermistor (TH) 103 for the semiconductor laser shown in FIG. Is omitted. These are the respective semiconductor lasers 101. ₁ , 101 ₂ , 101 ₃ , ... are provided individually.
[0048]
In the semiconductor laser degradation monitoring apparatus 100A shown in FIG. 5, the DSP 112A includes an optical multiplexer 331 that is a semiconductor laser 101. ₁ , 101 ₂ , 101 ₃ ,... Is recognized by the semiconductor laser selection information 332 to select and output. Therefore, the error data 117 input from the wavelength locker 114 is converted into the semiconductor laser 101. ₁ , 101 ₂ , 101 ₃ , ... can be managed on a time-sharing basis. Control of the DSP 112A for each semiconductor laser 101 is as described in FIG. 2 of the previous embodiment. Further, the semiconductor laser 101 corresponding to this of the server 122A. ₁ , 101 ₂ , 101 ₃ ,... Is as described with reference to FIG.
[0049]
Therefore, the server 122A includes the semiconductor laser 101. ₁ , 101 ₂ , 101 ₃ It is possible to manage the lifetime for each of, ... in a lump. The display screen showing the lifetime is the semiconductor laser 101. ₁ , 101 ₂ , 101 ₃ ..,... May be sequentially switched and displayed, or the semiconductor laser 101 may be displayed. ₁ , 101 ₂ , 101 ₃ When the total number of... Is relatively small, these may be displayed in a divided screen. Alternatively, only the semiconductor laser 101 that is approaching the end of life may be displayed exclusively on a specific screen or a specific image display area to prompt replacement.
[0050]
<Second Modification of First Embodiment>
[0051]
FIG. 6 shows display contents displayed by the server in the second modification of the first embodiment of the present invention. In step S146 of FIG. 2 of the first embodiment, a new set temperature T _set Is set to the server 122 (see FIG. 1), the elapsed time t from the start of use of the semiconductor laser 101 and the error Δλ. _mon In addition, the temperature ΔT and the driving current I of the semiconductor laser 101 shown in the equation (2) were sent out. In the second modification, not only the curve 181 showing the secular change of the wavelength shift in FIG. 4 but also the curve 182 showing how the value of the drive current of the semiconductor laser 101 fluctuates and every time data is transmitted to the server 122. Is set temperature T calculated by equation (2) based on temperature ΔT sent to _set The change over time is shown.
[0052]
Therefore, a person who manages the lifetime of the semiconductor laser 101 can predict the lifetime by referring to not only the curve 181 but also other curves 381 and 382. For example, when the amount of change in the drive current I of the semiconductor laser 101 becomes equal to or greater than a certain amount or the amount of change in the temperature T exceeds a certain value, it can be used as a judgment material when determining the lifetime.
[0053]
<Third Modification of First Embodiment>
[0054]
FIG. 7 shows an outline of the configuration of an optical communication system using a semiconductor laser deterioration monitoring apparatus as a third modification of the first embodiment of the present invention. In this optical communication system, each optical transmission unit 401 in the optical transmitter 400 connected to an optical transmission device (not shown) arranged on the transmission side. ₁ ~ 401 _N Wavelength λ sent from ₁ ~ Λ _N The optical signals for N channels are multiplexed by an optical multiplexer (MUX) unit 402, amplified by a booster amplifier 403, and sent to an optical transmission line 404. The multiplexed optical signal 405 is appropriately amplified by an in-line amplifier 406, and then passes through a preamplifier 407 and is then transmitted to an original wavelength λ by an optical demultiplexer (DMUX) 408. ₁ ~ Λ _N And each optical receiver 410 in the optical receiver 409. ₁ ~ 410 _N Received by the corresponding one of
[0055]
The optical transmitter 400 is substantially provided with a DSP 112A, a wavelength locker 114, and an optical coupler 115 having the same configuration as that of the first modification shown in FIG. 5, and data 123B is stored in the server 122B. ₁ Is sent out. Here, the semiconductor laser 101 in FIG. ₁ , 101 ₂ , 101 ₃ ,... Are the optical transmission unit 401 in FIG. ₁ ~ 401 _N It corresponds to. The server 122B receives data 123B from not only the optical transmitter 400 but also from another optical transmitter having the same configuration (not shown). ₂ ~ Data 123B _N The life or deterioration of a large number of semiconductor lasers (not shown) in a plurality of optical communication systems is monitored.
[0056]
FIG. 8 shows an example of a monitor screen displayed on the display of the semiconductor laser deterioration monitoring apparatus employed in such an optical communication system. On the display 451, the monitoring results of the semiconductor lasers of all the channels in each optical communication system are displayed. Here, the 160-channel CH that constitutes one optical communication system called system A ₁ ~ CH ₁₆₀ The monitoring result is displayed.
[0057]
Each semiconductor laser whose lifetime has been determined from the characteristic diagram shown in FIG. 4 of the embodiment is classified into a plurality of groups according to the years that can be used until the lifetime is reached. Each character or background color is displayed in a color for each group.
[0058]
It is also possible to individually display the characteristic diagram shown in FIG. 4 for the corresponding semiconductor laser by clicking the characters of the displayed channels. In FIG. 8, the states of the semiconductor lasers are displayed in the order of the channel numbers. However, it is possible to make a modification in which the states are displayed in the order in which the lifetimes approach.
[0059]
<Second embodiment>
[0060]
FIG. 9 shows the configuration of a semiconductor laser deterioration monitoring apparatus according to the second embodiment of the present invention. In FIG. 9, the same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate. In the semiconductor laser deterioration monitoring apparatus 500 of this embodiment, an injection current control circuit 502 that performs both monitoring and control of the injection current 501 of the semiconductor laser 101 is provided. The temperature control circuit unit (ATC) 104C controls the semiconductor laser 101 to a predetermined temperature. In this embodiment, the wavelength shift due to the deterioration of the laser with time is corrected not by the temperature but by the injection current, and the deterioration of the semiconductor laser is determined when the total of the correction values of the injection current becomes a certain value or more.
[0061]
FIG. 10 shows the operation of the DSP and corresponds to FIG. 3 of the first embodiment. When the power of the semiconductor laser deterioration monitoring apparatus 500 is turned on, the DSP 112C starts its control operation. First, the monitor injection current i of the injection current control circuit 502 is started. _mon Is the set injection current i for the semiconductor laser 101 _set Is checked (step S541). Monitor injection current i _mon Is the set injection current i _set Is not equal to (N), the control of the injection current by the injection current control circuit 502 waits for them to be equal.
[0062]
In this way, the monitor injection current i _mon Is the set injection current i _set (Step S541: Y), the DSP 112C inputs various information from the wavelength locker 114 or the like (step S542). Then, using the error data 117 output from the wavelength locker 114, the target wavelength λ _A And the error Δλ of the actually monitored wavelength λ _mon Whether or not is zero is determined (step S543). These relationships are as shown in equation (1) of the first embodiment.
[0063]
The wavelength λ that is actually monitored is the target wavelength λ _A (Step S543: Y), the process returns to step S541 and the process is continued (return). On the other hand, the actually monitored wavelength λ is the target wavelength λ. _A I.e., the error Δλ _mon Is not zero (N), the set injection current i obtained by adding the injection current Δi shown in the following equation (3) so that it becomes zero _set Is calculated (step S544).
[0064]
i _set = I _ini + Δi (3)
[0065]
However, i _ini Is the initial value i of the injection current of the semiconductor laser 101. _ini It is. This initial value i _ini Is determined by observing the wavelength output from the semiconductor laser 101 (FIG. 9) with a wavelength meter (not shown) at the time of initialization, and is input to the DSP 112C from a keyboard or operation panel (not shown).
[0066]
The DSP 112C uses the set injection current i calculated by the equation (3). _set Is sent to the injection current control circuit 502 as injection current data 504 (step S545). The elapsed time t from the start of use of the semiconductor laser 101 and the error Δλ _mon Are sent to the server 122 (step S546), and the process returns to step S541 again (return).
[0067]
When the server 122C side manages the elapsed time t from the start of use of the semiconductor laser 101 and knows the time, it is not necessary to transmit this to the server 122C.
[0068]
As described above, in the semiconductor laser deterioration monitoring apparatus 500, the injection current of the semiconductor laser 101 is set to the set injection current i. _set Is obtained at the first time, and various information such as the drive current I is acquired, and the monitored wavelength λ is the target wavelength λ. _A If it is equal to, control is continued such that the injection current by the injection current control circuit 502 or the like becomes constant in that state. Then, the wavelength λ monitored by the secular change of the semiconductor laser 101 is the target wavelength λ. _A If the difference between the two values exceeds a certain allowable value, a new set injection current i _set In this state, the current predetermined data is transmitted to the server 122C.
[0069]
For example, when the semiconductor laser 101 is new, the wavelength λ monitored in step S543 is the target wavelength λ. _A Depending on the product, it will usually take several years until it conflicts. In the meantime, the server 122C does not receive data from the DSP 112C, and during this time, the server 122C concentrates on other work. Then, when the data shown in step S546 is sent from the DSP 112C, control for predicting the lifetime of the corresponding semiconductor laser 101 is performed.
[0070]
The control on the server 122C side in this embodiment is not essentially different from the control in the first embodiment shown in FIG. Therefore, explanation about this is omitted.
[0071]
<Other variations>
[0072]
Further, it is possible to detect the increase in the driving current of the semiconductor laser and display the lifetime by using the date and time when the driving current is shifted by a predetermined amount or more as the deterioration threshold of the semiconductor laser. That is, if the same optical output power is maintained by performing APC control regardless of the deterioration of the semiconductor laser over time, it is necessary to increase the drive current of the semiconductor laser. The relationship between the driving current of the semiconductor laser and the wavelength shift can be regarded as almost the same, although there are some variations depending on the semiconductor laser. Since the wavelength shift occurs due to the increase of the drive current, the degree of increase of the drive current can be used for the life determination or display. For example, when the driving current of the semiconductor laser is increased by 10 mA (milliampere), the wavelength is shifted by 0.1 nm (nanometer). At that time, the increase in current can be monitored, and the life can be displayed using the date and time when the current increases, for example, 10 mA as the LD degradation threshold. In the case of this modification, it is not necessary to adjust the temperature to correct the wavelength shift.
[0073]
In the embodiments and modifications of the present invention, the deterioration or life of the semiconductor laser is monitored using a CPU or DSP and a server. However, the control is not divided into two in this way. It is also possible to consistently perform graph creation and life prediction using a CPU or DSP.
[0074]
【The invention's effect】
As described above, according to the first to seventh aspects of the present invention, when a relatively short period has elapsed since the start of the use of the semiconductor laser, the progress of deterioration or initial failure is based on the history data. Can be checked. Furthermore, since the history data is added each time the characteristic mismatch determination means determines that it does not match the target value, it is possible to gradually monitor with high accuracy.
[0075]
According to the invention of claim 2 or claim 4, since the graph display means displays the state of deterioration of the semiconductor laser on the graph based on the respective history data created by the history data creation means. You can visually grasp the progress. Therefore, it is possible to determine when the semiconductor laser should be replaced, and efficient or economical replacement becomes possible.
[0076]
According to the fifth aspect of the present invention, since the curve passing through the coordinate point indicating the history data is displayed when the graph is displayed, the state of future deterioration can be predicted and displayed. At this time, the lifetime and the like can be easily determined by indicating the time corresponding to the point at which this curve reaches the deterioration value indicating the deterioration with the predetermined characteristics of the semiconductor laser.
[0077]
Further, according to the invention described in claim 7, when a plurality of semiconductor lasers are used as in the case of performing wavelength division multiplex transmission, since the progress of these deteriorations is monitored by time division or the like, hardware is saved, An economical semiconductor laser deterioration monitoring device can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the configuration of a semiconductor laser deterioration monitoring apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart showing how a DSP of this embodiment is controlled.
FIG. 3 is a flowchart showing the flow of processing on the server side when data is transmitted from the DSP in this embodiment.
FIG. 4 shows elapsed time t and cumulative λ displayed by the server in the present embodiment. _dev It is a characteristic view showing an example of the characteristic.
FIG. 5 is a block diagram showing a configuration of a semiconductor laser deterioration monitoring apparatus in a first modification of the first embodiment of the present invention.
FIG. 6 is a characteristic diagram showing display contents displayed by the server in a second modification of the first embodiment of the present invention.
FIG. 7 is a system configuration diagram showing an outline of a configuration of an optical communication system using a semiconductor laser deterioration monitoring apparatus according to a third modification of the first embodiment of the present invention.
FIG. 8 is a main part plan view showing an example of a monitor screen displayed on a display of a semiconductor laser deterioration monitoring apparatus in a third modified example.
FIG. 9 is a block diagram showing the configuration of a semiconductor laser deterioration monitoring apparatus in a second embodiment of the present invention.
FIG. 10 is a flowchart showing the operation of the DSP in the second embodiment.
[Explanation of symbols]
100, 100A, 500 Semiconductor laser degradation monitoring device
101 Semiconductor laser (LD)
102 Peltier element (PE)
103 Thermistor (TH)
104 Temperature control circuit (ATC)
106 Power constant control circuit (APC)
112, 112A, 112C DSP
114 wavelength rocker
115 Optical coupler
122, 122A, 122B, 122C server
451 display
502 Injection Current Control Circuit

Claims (7)

A temperature control circuit for controlling the temperature of the semiconductor laser to a set temperature;
A time measuring means for measuring the usage time from the start of use of the semiconductor laser;
When a new set temperature is applied and the temperature control circuit causes the semiconductor laser to reach a new set temperature, a predetermined characteristic predetermined for the semiconductor laser is set for each semiconductor laser. Characteristic mismatch determination means for determining whether or not the value differs,
Error calculating means for obtaining an error from the target value when it is determined that the characteristic mismatch determining means does not match the target value;
History data creating means for creating history data in which the accumulated value of the error by the error calculation means from the start of use of the semiconductor laser and the corresponding use time of the semiconductor laser are paired;
Use time determining means for determining a use time until the predetermined characteristic of the semiconductor laser reaches a deterioration value indicating deterioration of the semiconductor laser, using each history data generated by the history data generating means; A semiconductor laser deterioration monitoring device. A temperature control circuit for controlling the temperature of the semiconductor laser to a set temperature;
A time measuring means for measuring the usage time from the start of use of the semiconductor laser;
When a new set temperature is applied and the temperature control circuit causes the semiconductor laser to reach a new set temperature, a predetermined characteristic predetermined for the semiconductor laser is set for each semiconductor laser. Characteristic mismatch determination means for determining whether or not the value differs,
Error calculating means for obtaining an error from the target value when it is determined that the characteristic mismatch determining means does not match the target value;
History data creating means for creating history data in which the accumulated value of the error by the error calculation means from the start of use of the semiconductor laser and the corresponding use time of the semiconductor laser are paired;
Semiconductor laser deterioration monitoring, comprising: graph display means for displaying each history data created by the history data creating means on a graph with an error in the predetermined characteristic and a usage time as coordinate axes, respectively. apparatus. An injection current control circuit for controlling the injection current for the semiconductor laser to a predetermined set injection current value;
A time measuring means for measuring the usage time from the start of use of the semiconductor laser;
When a new set injection current value is given and the injection current control circuit causes the semiconductor laser to reach a new set injection current value, a predetermined characteristic predetermined for the semiconductor laser is applied to each semiconductor laser. Characteristic mismatch determination means for determining whether or not the target value determined by
Error calculating means for obtaining an error from the target value when it is determined that the characteristic mismatch determining means does not match the target value;
History data creating means for creating history data in which the accumulated value of the error by the error calculation means from the start of use of the semiconductor laser and the corresponding use time of the semiconductor laser are paired;
Use time determining means for determining a use time until the predetermined characteristic of the semiconductor laser reaches a deterioration value indicating deterioration of the semiconductor laser, using each history data generated by the history data generating means; A semiconductor laser deterioration monitoring device. An injection current control circuit for controlling the injection current for the semiconductor laser to a predetermined set injection current value;
A time measuring means for measuring the usage time from the start of use of the semiconductor laser;
When a new set injection current value is given and the injection current control circuit causes the semiconductor laser to reach a new set injection current value, a predetermined characteristic predetermined for the semiconductor laser is applied to each semiconductor laser. Characteristic mismatch determination means for determining whether or not the target value determined by
Error calculating means for obtaining an error from the target value when it is determined that the characteristic mismatch determining means does not match the target value;
History data creating means for creating history data in which the accumulated value of the error by the error calculation means from the start of use of the semiconductor laser and the corresponding use time of the semiconductor laser are paired;
Semiconductor laser deterioration monitoring, comprising: graph display means for displaying each history data created by the history data creation means on a graph with an error in the predetermined characteristic and a usage time as coordinate axes, respectively. apparatus. The graph display means displays a curve passing through the coordinate point indicating each history data, and also displays a usage time for the curve to reach a deterioration value indicating deterioration by a predetermined characteristic of the semiconductor laser. The semiconductor laser deterioration monitoring apparatus according to claim 2 or 4, characterized in that: 5. The semiconductor according to claim 1, wherein the predetermined characteristic is a wavelength output from a semiconductor laser, and the error calculated by the error calculating means is a wavelength error from a target value. Laser degradation monitoring device. 5. The semiconductor laser deterioration monitoring apparatus according to claim 1, further comprising means for sequentially monitoring the deterioration of the plurality of semiconductor lasers with different processing times.

Images