A method for initial wavelength calibration and wavelength locking of a tunable laser

Abstract

The application discloses a kind of initial wavelength calibration and wavelength locking method of tunable laser, belong to laser control technical field.The application finds the best current value of wavelength selection area that satisfies wavelength error condition by particle swarm-ant colony hybrid algorithm, and the corresponding actual wavelength is used as initial wavelength;For tunable laser that completes initial wavelength calibration, the phase shift curve of initial wavelength is linearly interpolated, the current value of wavelength selection area of protocol wavelength and the current value of phase control area are obtained, for setting the current of wavelength selection area and phase control area of tunable laser;Using proportional-integral-derivative control algorithm, according to the current environmental temperature adjustment TEC1 temperature, the current actual wavelength of tunable laser is locked in the target range around protocol wavelength.The application greatly improves the reliability of initial wavelength calibration, while ensuring the stable output of tunable laser wavelength.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser control, and particularly relates to an initial wavelength calibration and wavelength locking method of a tunable laser. BACKGROUND

[0002] The tunable laser changes the waveguide temperature by regulating the thermal power of the eight waveguide arms, so that the refractive index of the waveguide core layer changes. This change in refractive index causes the optical path difference of the eight waveguide arms to be adjusted accordingly, so that the tunable laser generates light beams of different wavelengths, realizing the function of wavelength adjustment. In the implementation process, the tunable laser needs to be calibrated, and the calibration data is written into the flash memory. The tunable laser calibration process includes:

[0003] (1) current and voltage curve scanning;

[0004] (2) initial wavelength calibration;

[0005] (3) phase shift period scanning of the eight waveguide arms;

[0006] (4) taking the current value of the eight waveguide arms corresponding to the initial wavelength as the starting point, stepping the current value of the eight waveguide arms to obtain the phase shift curve of the eight waveguide arms;

[0007] (5) interpolating the current value of the eight waveguide arms corresponding to all protocol wavelengths according to the phase shift curve.

[0008] Among them, the initial wavelength calibration is an important step in the laser calibration process, which affects the final wavelength output accuracy.

[0009] However, the related art usually calibrates the initial wavelength according to human experience. Due to the differences between different tunable lasers, the initial wavelength calibrated based on experience will cause the current value of the eight waveguide arms corresponding to the protocol wavelength of the individual tunable laser to be greatly different from the actual required current value, thereby resulting in poor final wavelength output accuracy. Therefore, the related art has the technical problem of poor reliability of initial wavelength calibration.

[0010] In addition, in the related art, the tunable laser will drift in wavelength in a working environment with large environmental temperature fluctuations, and cannot realize stable wavelength output. SUMMARY

[0011] The main purpose of the present application is to provide an initial wavelength calibration and wavelength locking method of a tunable laser, aiming at solving the technical problems of poor reliability of initial wavelength calibration of the tunable laser and wavelength drift caused by environmental temperature fluctuations in the related art.

[0012] To achieve the above object, the application provides an initial wavelength calibration and wavelength locking method of a tunable laser, which comprises the following steps:

[0013] S1, for each tunable laser, the particle swarm-ant colony hybrid algorithm is used to find the optimal current value of the wavelength selection zone meeting the wavelength error condition, and the actual wavelength corresponding to the optimal current value of the wavelength selection zone is taken as the initial wavelength;

[0014] S2, for the tunable laser whose initial wavelength is calibrated, the phase shift curve of the initial wavelength is linearly interpolated to obtain the current value of the wavelength selection zone and the current value of the phase control zone corresponding to the protocol wavelength;

[0015] S3, the current value of the wavelength selection zone and the current value of the phase control zone of the tunable laser are set to the current value of the wavelength selection zone and the current value of the phase control zone corresponding to the protocol wavelength respectively, so that the tunable laser outputs the protocol wavelength; the proportional-integral-derivative control algorithm is used to adjust the TEC1 temperature according to the current environmental temperature, and the current actual wavelength of the tunable laser is locked in the target range around the protocol wavelength.

[0016] The particle swarm-ant colony hybrid algorithm is used to find the current value of the wavelength selection zone meeting the wavelength error condition, the optimal current value of the wavelength selection zone required for the tunable laser to output the protocol wavelength can be determined for different tunable lasers, thereby the initial wavelength of different tunable lasers can be calibrated in a targeted manner, and the reliability of the initial wavelength calibration is greatly improved. On this basis, the protocol wavelength can be accurately calibrated based on the initial wavelength. Meanwhile, the TEC1 temperature is adjusted according to the current environmental temperature through the proportional-integral-derivative control algorithm, the TEC1 temperature can be corrected in real time according to the current environmental temperature, thereby the current actual wavelength of the tunable laser can be locked in the target range around the protocol wavelength in the working environment with temperature fluctuation, and the stable output of the tunable laser wavelength is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 It is a flowchart of the initial wavelength calibration and wavelength locking method of the tunable laser of the application;

[0018] Figure 2 It is a structural schematic diagram of the tunable laser.

[0019] The implementation, functional features and advantages of the application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0020] It is to be understood that the specific embodiments described herein are merely illustrative of the present application and do not limit the scope of the application. The present application will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration and

[0021] Referring to Figure 1 , the embodiment of the present application provides a method for initial wavelength calibration and wavelength locking of a tunable laser, comprising the following steps:

[0022] Step S1: for each tunable laser, find the optimal current value of the wavelength selection region that meets the wavelength error condition through a particle swarm-ant colony hybrid algorithm, and take the actual wavelength corresponding to the optimal current value of the wavelength selection region as the initial wavelength.

[0023] As Figure 2 shown in the embodiment, the tunable laser has a first thermoelectric cooler TEC1 and a second thermoelectric cooler TEC2. The laser chip is placed on the first thermoelectric cooler TEC1, and the laser chip includes 7 wavelength selection regions AP (including AP1, AP2, AP4, AP5, AP6, AP7, AP8), a phase control region CP, a light gain region GAIN, and a light amplification region SOA. The first photodetector PD1 and the second photodetector PD2 are placed on the second thermoelectric cooler TEC2, and are used to monitor the optical power of the tunable laser before and after the etalon, respectively, and feed back the feedback current corresponding to the optical power. The S parameter of the tunable laser can be calculated through the feedback current, and the S parameter is used to monitor the shift of the output wavelength.

[0024] The step S1 specifically comprises the following steps:

[0025] Step S11: set the initial current value of the 7 wavelength selection regions to form a current value vector.

[0026] Step S12: set the number of particles of the particle swarm, and iteratively update the current value vector of the wavelength selection region through a particle update formula, and measure the actual wavelength corresponding to the current value vector in each iteration in real time.

[0027] The iteration process of the particle update formula is:

[0028] ;

[0029] ;

[0030] wherein, v i t represents the velocity of the i th particle in the t th iteration; v i t+1 represents the velocity of the i th particle in the t+1 th iteration; w represents the inertia weight; c1, c2, c3 represent the learning factor; r1, r2, r3 represent random numbers between 0 and 1; pdest iPdest represents the individual optimal solution; pdest g P represents the global optimal solution; P max Popt represents the optimal current value vector of the wavelength selection region, that is, the current value vector with the maximum pheromone concentration value in the current value vectors of the five tunable lasers after the initial wavelength calibration process, which is taken as the optimal current value vector of the tunable laser; Pi represents the position of the i-th particle in the t-th iteration, that is, the current value vector of the wavelength selection region in the t-th iteration; Pi+1 represents the position of the i-th particle in the t+1-th iteration, that is, the current value vector of the wavelength selection region in the t+1-th iteration.

[0031] Step S13: determining whether the actual wavelength satisfies the wavelength error condition, if not, continuing the iteration of the particle update formula, if yes, obtaining the final current value vector and entering step S14.

[0032] The wavelength error condition refers to that the wavelength difference between the actual wavelength and the protocol wavelength is less than the preset wavelength error, and the protocol wavelength is the target wavelength that the tunable laser needs to output. When the wavelength difference between the actual wavelength and the protocol wavelength is less than the preset wavelength error, it is indicated that the wavelength error condition is satisfied, and the iteration of the particle update formula is stopped, and step S14 is entered.

[0033] The pheromone concentration value of the final current value vector is calculated as follows:

[0034]

[0035] Wherein, T represents the pheromone concentration value of the current value vector; represents the wavelength difference; represents the target wavelength; represents the actual wavelength.

[0036] The pheromone concentration values of the final current value vectors of the first four tunable lasers in the initial wavelength calibration process are updated, and the current value vector corresponding to the maximum pheromone concentration value in the updated pheromone concentration values of the four tunable lasers and the pheromone concentration value calculated in step S13 is taken as the optimal current value vector:

[0037]

[0038] Wherein, k represents the index of the k-th tunable laser, k=1, 2, 3, 4; T k represents the pheromone concentration value of the k-th tunable laser before updating; represents the pheromone concentration value of the k-th tunable laser after updating; P represents the evaporation rate, 0 ​​​

[0039] For example, the pheromone concentration value of the 5th tunable laser is calculated in step S13, and the pheromone concentration values of the 1st, 2nd, 3rd and 4th tunable lasers have been calculated before. When k = 1, it means that the pheromone concentration value of the 1st tunable laser is updated using the evaporation rate P, and the rest is the same, which will not be repeated here.

[0040] In this way, the pheromone concentration values of the 5th tunable laser are obtained, and the current value vector corresponding to the tunable laser with the maximum pheromone concentration value is selected as the optimal current value vector P max , which acts on step S12.

[0041] Step S14: Adjust the current values of the 7 wavelength selection regions in the final current value vector by a quadratic fitting optimization algorithm to maximize the optical power of the tunable laser, obtain the optimal current values of the wavelength selection regions, complete the initial wavelength calibration of the tunable laser, and thus obtain the initial wavelength.

[0042] Step S14-1: After obtaining the final current value vector, the current value of each wavelength selection region is dithered within a preset dithering range based on a fixed step to obtain a current-optical power sequence of the wavelength selection region.

[0043] Step S14-2: Fit a quadratic curve to the current-optical power sequence, and the ordinate of the fitted quadratic curve is the optical power and the abscissa is the corresponding current value. The current value corresponding to the maximum optical power is taken as the target current value. If the target current value is equal to the current value of the wavelength selection region in the final current value vector of step S13, the current value of the wavelength selection region in the final current value vector is taken as the optimal current value. If not, go to step S14-3.

[0044] The formula of the fitting is:

[0045] ;

[0046] Where y represents the optical power; x represents the corresponding current value; A, B, C represent the coefficients obtained by fitting.

[0047] Step S14-3: Take the target current value as the current value of the corresponding wavelength selection region of the tunable laser in step S14-1, and return to execute step S14-1 until the optimal current value is obtained.

[0048] As an example: the 7 current values corresponding to the 7 wavelength selection regions in the final current value vector obtained in step S13 are x1, x2, x3, x4, x5, x6 and x7 respectively. Taking the optimization process of the current value x1 as an example, first, the current value x1 is dithered 7 times within the preset dithering range (for example, plus or minus 2 mA), and x 11 , x 12 , x 13 , x 14 , x 15 , x 16 , x 17 , and the corresponding optical power are obtained. The obtained current values and optical power are fitted to a quadratic curve, the abscissa of the quadratic curve is the current value, and the ordinate is the optical power. The target current value x g corresponding to the maximum optical power is obtained from the quadratic curve. If x g is equal to x1, then the current value x1 is taken as the optimal current value of the wavelength selection region. If not, the target current value x g is used to replace the current value x1, and the above steps are repeated until the optimal current value of the wavelength selection region is obtained.

[0049] Step S14-4: repeat steps S14-1 to S14-3 until the optimization of the current values of the 7 wavelength selection regions is completed, thereby obtaining the initial wavelength of the tunable laser.

[0050] During the entire step S14, the current values of the 7 wavelength selection regions in the final value vector are optimized by the binary fitting optimization algorithm, that is, the current value that maximizes the optical power of the tunable laser is found within the preset dithering range of the current value of the wavelength selection region, as the optimal current value of the wavelength selection region, so that the initial wavelength obtained finally not only meets the wavelength error condition of the tunable laser, but also ensures the optimal optical power of the tunable laser.

[0051] In the entire step S1, according to the wavelength error condition, the value vector corresponding to the optimal current value of the wavelength selection region is found by the particle swarm algorithm, which can accurately calibrate the initial wavelength of different tunable lasers. During the process, the current value of the wavelength selection region of the tunable laser is further optimized and adjusted by using the ant colony algorithm in combination with the optimal current value of the wavelength selection region corresponding to the five recently calibrated tunable lasers, which can improve the robustness of the initial wavelength calibration and further ensure the reliability of the initial wavelength calibration.

[0052] Step S2: for the tunable laser whose initial wavelength is calibrated, the phase shift curve of the initial wavelength is linearly interpolated to obtain the current value of the wavelength selection region and the current value of the phase control region corresponding to the protocol wavelength.

[0053] Specifically, the current values of the eight waveguide arms of the initial wavelength are adjusted by a fixed adjustment amount, and the current values of the eight waveguide arms are the optimal current values of the seven wavelength selection zones and the current value of the phase control zone CP; then the current values of the eight waveguide arms are optimized by a quadratic fitting algorithm. A set of current values (i.e. the current values of the eight waveguide arms) and corresponding wavelengths after adjustment and optimization can be obtained, and multiple sets of current values and corresponding wavelengths can be finally obtained through multiple adjustment and optimization.

[0054] The current values and corresponding wavelengths of each waveguide arm are fitted respectively, and eight current-wavelength curves corresponding to the eight waveguide arms are obtained, i.e. the phase shift curve of the initial wavelength.

[0055] The phase shift curve of the initial wavelength is linearly interpolated to establish a wavelength-current value lookup table.

[0056] The current value corresponding to the protocol wavelength is searched from the wavelength-current value lookup table, including the current values of the seven wavelength selection zones and the current value of the phase control zone.

[0057] Step S3: setting the wavelength selection zone current and the phase control zone current of the tunable laser to the current value of the wavelength selection zone corresponding to the protocol wavelength and the current value of the phase control zone, so that the tunable laser outputs the protocol wavelength; using a proportional-integral-derivative control algorithm to adjust the TEC1 temperature according to the current environmental temperature, and locking the current actual wavelength of the tunable laser within the target range around the protocol wavelength.

[0058] Step S31: setting the wavelength selection zone current of the tunable laser to the current value of the wavelength selection zone corresponding to the protocol wavelength, and setting the phase control zone current of the tunable laser to the current value of the phase control zone corresponding to the protocol wavelength, so that the tunable laser outputs the protocol wavelength.

[0059] Step S32: adjusting the TEC1 temperature under normal temperature, high temperature and low temperature environmental temperatures respectively, so that the actual wavelength corresponding to the TEC1 temperature has a wavelength difference with the protocol wavelength less than a preset wavelength error, reading the feedback currents of the first photodetector and the second photodetector respectively, and calculating three S parameters based on the feedback currents and the S parameter calculation formula, which are the normal temperature S parameter S0, the low temperature S parameter S1 and the high temperature S parameter S2; the normal temperature is 25℃, the high temperature is a temperature greater than 25℃ and less than 40℃, and the low temperature is a temperature greater than 5℃ and less than 25℃:

[0060] ;

[0061] Wherein, S represents the S parameter; I1 represents the feedback current of the first photodetector; I2 represents the feedback current of the second photodetector.

[0062] It is worth mentioning that the numerator term "I1-I2" of the S parameter calculation formula represents the difference between the transmitted and reflected light intensities of the laser, which has a linear relationship with the wavelength shift; the denominator term "I1+I2" represents the total light intensity, which is used to eliminate the influence of the output power fluctuation of the tunable laser on the S parameter. For example, when the power fluctuation causes I1 and I2 to increase and decrease synchronously, the ratio of the numerator term to the denominator term S remains unchanged, only reflecting the wavelength change. Therefore, the S parameter can be used to monitor the shift of the output wavelength.

[0063] Step S33: Collect the current environmental temperature, and calculate the S parameter correction value corresponding to the protocol wavelength at the current environmental temperature based on the three S parameters:

[0064] ;

[0065] wherein, T represents the current environmental temperature; T1 represents the low-temperature environmental temperature; and T2 represents the high-temperature environmental temperature. S represents the S parameter correction value corresponding to the protocol wavelength at the current environmental temperature.

[0066] In the process of steps S32 to S33, the S parameters of the tunable laser under normal temperature, high temperature and low temperature environments are calculated respectively, that is, the best S parameters that meet the wavelength error condition under different environmental temperatures, so as to calculate the best S parameter of the tunable laser under the current environmental temperature in combination with the current environmental temperature and the best S parameter, that is, the S parameter correction value, which can accurately calculate the best S parameter under the current environmental temperature, and lays a foundation for the accurate adjustment of the TEC1 temperature.

[0067] Step S34: Read the feedback currents of the first photodetector and the second photodetector under the current actual wavelength, and calculate the S parameter corresponding to the current actual wavelength.

[0068] Step S35: Calculate the TEC1 temperature adjustment value based on the parameter difference between the S parameter correction value and the S parameter corresponding to the current actual wavelength by using the proportional-integral-derivative control algorithm:

[0069] , ;

[0070] wherein, u k represents the TEC1 temperature adjustment value, that is, the kth PID adjustment result; K p represents the proportional gain; K i represents the integral gain; K d represents the differential gain; e k-1 represents the parameter difference after the k-1th PID adjustment; e k-2 represents the parameter difference after the k-2th PID adjustment; and e jS represents the parameter difference after the jth PID adjustment. c,k-1 S represents the S parameter corresponding to the current actual wavelength after the k-1th PID adjustment.

[0071] Step S36: Adjust the TEC1 temperature based on the TEC1 temperature adjustment value, so that the value of the S parameter is maintained in the target range around the S parameter correction value, thereby locking the current actual wavelength in the target range around the protocol wavelength:

[0072] ;

[0073] wherein, S represents the adjusted TEC1 temperature. S represents the unadjusted TEC1 temperature.

[0074] Specifically, adjusting the TEC1 temperature can control the temperature of the laser chip, and further control the wavelength output of the tunable laser, and the wavelength deviation can be monitored by the S parameter. Therefore, in the adjustment process, the value of the S parameter is maintained in the target range around the S parameter correction value, so that the current actual wavelength can be locked in the target range around the protocol wavelength.

[0075] In the embodiment, the current value of the wavelength selection area that meets the wavelength error condition is found by the particle swarm-ant colony hybrid algorithm, and the optimal current value of the wavelength selection area required for the tunable laser to output the protocol wavelength can be determined for different tunable lasers, so that the initial wavelength of different tunable lasers can be calibrated in a targeted manner, greatly improving the reliability of the initial wavelength calibration. On this basis, the protocol wavelength can be accurately calibrated based on the initial wavelength. At the same time, the TEC1 temperature is adjusted according to the current environmental temperature by the proportional-integral-derivative control algorithm, so that the TEC1 temperature can be corrected in real time according to the current environmental temperature, thereby the current actual wavelength of the tunable laser can be locked in the target range around the protocol wavelength in the working environment with temperature fluctuation, and the stable output of the tunable laser wavelength is ensured.

[0076] The above-mentioned serial numbers of the embodiments of the present application are only for description, and do not represent the advantages and disadvantages of the embodiments.

[0077] The above is only the preferred embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent flow transformation based on the content of the specification and drawings, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the present application.

Claims

1. A method for initial wavelength calibration and wavelength locking of a tunable laser, characterized in that: The method comprises the following steps: S1, for each tunable laser, find the optimal current value of the wavelength selection zone that meets the wavelength error condition through the particle swarm-ant colony hybrid algorithm, and use the actual wavelength corresponding to the optimal current value of the wavelength selection zone as the initial wavelength; Said S1 specifically includes: S11, setting the initial current values ​​of the seven wavelength selection zones to form a current value vector; S12, setting the number of particles in the particle swarm, iteratively updating the current value vector of the wavelength selection area through the particle update formula, and measuring the actual wavelength corresponding to the current value vector in each iteration in real time; ； ； in, represents the velocity of the i-th particle at the t-th iteration; represents the velocity of the i-th particle at the t-th iteration; w represents the inertia weight; c1, c2, c3 represent the learning factor; r1, r2, r3 represent random numbers between 0 and 1; pdest i represents the individual optimal solution; pdest g represents the global optimal solution; P max The optimal current value vector of the wavelength selection area is the current value vector with the largest pheromone concentration among the current value vectors obtained after the initial wavelength calibration process of the last five tunable lasers. This current value vector is used as the optimal current value vector of this tunable laser. represents the position of the i-th particle at the t-th iteration, which is also the current value vector of the wavelength selection area at the t-th iteration; represents the position of the i-th particle at the t+1th iteration, which is also the current value vector of the wavelength selection area at the t+1th iteration; S13, determine whether the actual wavelength meets the wavelength error condition. If not, continue to iterate the particle update formula. If so, obtain the final current value vector and proceed to step S14; S14, adjusting the current values ​​of the seven wavelength selection zones in the final current value vector by a quadratic fitting optimization algorithm to maximize the optical power of the tunable laser, obtain the optimal current value of the wavelength selection zone, complete the initial wavelength calibration of the tunable laser, and thus obtain the initial wavelength; S2, for the tunable laser that has completed the initial wavelength calibration, linearly interpolate the phase shift curve of the initial wavelength to obtain the current value of the wavelength selection area and the current value of the phase control area corresponding to the protocol wavelength; S3, setting the wavelength selection zone current and phase control zone current of the tunable laser to the wavelength selection zone current value and phase control zone current value corresponding to the protocol wavelength, so that the tunable laser outputs the protocol wavelength; using the proportional integral differential control algorithm to adjust the TEC1 temperature according to the current ambient temperature, and lock the current actual wavelength of the tunable laser within the target range around the protocol wavelength.

2. The method for initial wavelength calibration and wavelength locking of a tunable laser according to claim 1, wherein: After S13, the method further includes: Calculate the pheromone concentration value of the final current value vector: ， ； Where T represents the pheromone concentration value of the current value vector; Indicates wavelength difference; Indicates the target wavelength; Indicates the actual wavelength; Update the pheromone concentration values ​​of the final current value vectors of the first four tunable lasers during the initial wavelength calibration process, and select the current value vector corresponding to the maximum pheromone concentration value between the updated pheromone concentration values ​​of the four tunable lasers and the pheromone concentration values ​​calculated by S13 as the optimal current value vector: ； Where k represents the index of the kth tunable laser, k=1,2,3,4; T k represents the pheromone concentration value before the kth tunable laser is updated; represents the pheromone concentration value after the kth tunable laser is updated; P represents the evaporation rate, 0 <P<1。 3. The method for initial wavelength calibration and wavelength locking of a tunable laser according to claim 1, wherein: The S14 specifically includes: S14-1, after obtaining the final current value vector, dithering the current value of each wavelength selection zone within a preset dithering range based on a fixed step to obtain a current-optical power sequence for the wavelength selection zone; S14-2: Fit a quadratic curve to the current-optical power sequence, where the ordinate of the fitted quadratic curve is the optical power and the abscissa is the corresponding current value. The current value corresponding to the maximum optical power is used as the target current value. If the target current value is equal to the current value of the wavelength selection area in the final current value vector of step S13, the current value of the wavelength selection area in the final current value vector is used as the optimal current value. If they are not equal, proceed to step S14-3. S14-3, using the target current value as the current value of the wavelength selection region corresponding to the tunable laser in S14-1, and returning to S14-1 until the optimal current value is obtained; S14-4: Repeat S14-1 to S14-3 until the current values ​​of the seven wavelength selection regions are optimized, thereby obtaining the initial wavelength of the tunable laser.

4. The method for initial wavelength calibration and wavelength locking of a tunable laser according to claim 1, wherein: The S3 specifically includes: S31, setting the wavelength selection zone current of the tunable laser to the current value of the wavelength selection zone corresponding to the protocol wavelength, and setting the phase control zone current of the tunable laser to the current value of the phase control zone corresponding to the protocol wavelength, so that the tunable laser outputs the protocol wavelength; S32, adjusting the temperature of TEC1 at normal temperature, high temperature, and low temperature ambient temperatures, respectively, so that the wavelength difference between the actual wavelength corresponding to the TEC1 temperature and the protocol wavelength is less than a preset wavelength error, reading the feedback currents of the first photodetector and the second photodetector, respectively, and calculating three S parameters based on the feedback currents and an S parameter calculation formula, namely, a normal temperature S parameter S0, a low temperature S parameter S1, and a high temperature S parameter S2; the normal temperature is 25°C, the high temperature is a temperature greater than 25°C and less than 40°C, and the low temperature is a temperature greater than 5°C and less than 25°C: ； Wherein, S represents the S parameter; I1 represents the feedback current of the first photodetector; I2 represents the feedback current of the second photodetector; S33: Collect the current ambient temperature and calculate the S parameter correction value corresponding to the protocol wavelength at the current ambient temperature based on the three S parameters: ； in, Indicates the current ambient temperature; T1 indicates low ambient temperature; T2 indicates high ambient temperature; Indicates the S parameter correction value corresponding to the protocol wavelength at the current ambient temperature; S34, reading the feedback currents of the first photodetector and the second photodetector at the current actual wavelength, and calculating the S parameters corresponding to the current actual wavelength; S35, calculating the TEC1 temperature adjustment value based on the S parameter correction value and the parameter difference of the S parameter corresponding to the current actual wavelength through the proportional integral differential control algorithm; S36 , adjusting the temperature of TEC1 based on the TEC1 temperature adjustment value to maintain the S parameter value within a target range around the S parameter correction value, thereby locking the current actual wavelength within a target range around the agreed wavelength.

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