Initial wavelength calibration and wavelength locking method of tunable laser

Abstract

The invention discloses an initial wavelength calibration and wavelength locking method of a tunable laser, and belongs to the technical field of laser control. According to the method, the optimal current value of the wavelength selection area meeting the wavelength error condition is searched through the particle swarm-ant colony hybrid algorithm, and the corresponding actual wavelength is used as the initial wavelength; performing linear interpolation on the phase shift curve of the initial wavelength for the tunable laser with the initial wavelength calibrated to obtain a current value of a wavelength selection region and a current value of a phase control region of a protocol wavelength for setting the current of the wavelength selection region and the current of the phase control region of the tunable laser; and the TEC1 temperature is adjusted according to the current environment temperature by using a proportional-integral-derivative control algorithm, and the current actual wavelength of the tunable laser is locked in a target range around the protocol wavelength. According to the invention, the reliability of initial wavelength calibration is greatly improved, and stable output of the wavelength of the tunable laser is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of laser control, and in particular to a method for initial wavelength calibration and wavelength locking of a tunable laser. Background Art

[0002] Tunable lasers change the waveguide temperature by regulating the thermal power of the eight waveguide arms, thereby changing the refractive index of the waveguide core. This change in refractive index causes the optical path difference of the eight waveguide arms to adjust accordingly, allowing the tunable laser to generate beams of different wavelengths, achieving wavelength tunability. During this implementation, the tunable laser needs to be calibrated and the calibration data written to flash memory. The tunable laser calibration process includes:

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

[0004] (2) Initial wavelength calibration;

[0005] (3) Phase-shifted periodic scanning of the eight waveguide arms;

[0006] (4) Taking the current values of the eight waveguide arms corresponding to the initial wavelength as the starting point, the current values of the eight waveguide arms are stepped to obtain the phase shift curves of the eight waveguide arms;

[0007] (5) Interpolate the current values of the eight waveguide arms corresponding to all protocol wavelengths based on the phase shift curve.

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

[0009] However, related technologies typically calibrate the initial wavelength based on empirical values. Due to differences between tunable lasers, calibrating the initial wavelength based on empirical values can result in significant discrepancies between the current values in the eight waveguide arms corresponding to the agreed wavelength of individual tunable lasers and the actual required current values, leading to poor final wavelength output accuracy. Consequently, related technologies suffer from the technical issue of poor reliability in initial wavelength calibration.

[0010] In addition, in the related art, the wavelength of the tunable laser will drift when working in an environment with large ambient temperature fluctuations, and it is impossible to achieve stable wavelength output. Summary of the Invention

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

[0012] To achieve the above object, the present invention provides a method for initial wavelength calibration and wavelength locking of a tunable laser, the method comprising the following steps:

[0013] 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;

[0014] 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;

[0015] 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.

[0016] The present invention uses a particle swarm-ant colony hybrid algorithm to find the current value in the wavelength selection zone that satisfies the wavelength error condition. This allows for determining the optimal current value in the wavelength selection zone required for the output wavelength of different tunable lasers to achieve the actual agreed wavelength. This allows for targeted calibration of the initial wavelengths of different tunable lasers, significantly improving the reliability of initial wavelength calibration. Furthermore, the agreed wavelength can be accurately calibrated based on the initial wavelength. Furthermore, a proportional-integral-differential control algorithm is used to adjust the TEC1 temperature according to the current ambient temperature. This allows for real-time correction of the TEC1 temperature based on the current ambient temperature, thereby locking the actual wavelength of the tunable laser within a target range around the agreed wavelength in a temperature-fluctuating operating environment, ensuring stable output of the tunable laser wavelength. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the process of an embodiment of the method for initial wavelength calibration and wavelength locking of a tunable laser according to the present invention;

[0018] Figure 2 Schematic diagram of the structure of a tunable laser.

[0019] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0020] It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention. The inventive concept of the present application will be further described below with reference to some specific embodiments and implementation methods.

[0021] Reference Figure 1 The embodiment of the present invention 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, the particle swarm-ant colony hybrid algorithm is used to find the optimal current value of the wavelength selection area that meets the wavelength error condition, and the actual wavelength corresponding to the optimal current value of the wavelength selection area is used as the initial wavelength.

[0023] like Figure 2 As shown, in this embodiment, the tunable laser comprises a first thermoelectric cooler TEC1 and a second thermoelectric cooler TEC2. A laser chip is placed on the first thermoelectric cooler TEC1. The laser chip comprises seven wavelength-selective regions AP (including AP1, AP2, AP4, AP5, AP6, AP7, and AP8), a phase control region CP, an optical gain region GAIN, and an optical amplification region SOA. A first photodetector PD1 and a second photodetector PD2 are placed on the second thermoelectric cooler TEC2. These are used to monitor the optical power of the tunable laser before and after passing through the etalon, respectively, and to provide feedback current corresponding to the optical power. This feedback current can be used to calculate the S parameters of the tunable laser, which are used to monitor the output wavelength offset.

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

[0025] Step S11: setting initial current values of the seven wavelength selection zones to form a current value vector.

[0026] Step 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.

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

[0028] ;

[0029] ;

[0030] 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+1th iteration; w represents the inertia weight; c1, c2, c3 represent the learning factor; r1, r2, r3 represent random numbers between 0 and 1; pdest irepresents 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; It represents the position of the i-th particle in the t+1th iteration, which is also the current value vector of the wavelength selection area in the t+1th iteration.

[0031] Step 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.

[0032] The wavelength error condition refers to the wavelength difference between the actual wavelength and the agreed wavelength being less than a preset wavelength error. The agreed wavelength is the target wavelength to be output by the tunable laser. When the wavelength difference between the actual wavelength and the agreed wavelength is less than the preset wavelength error, the wavelength error condition is satisfied, and the iteration of the particle update formula is stopped, and the process proceeds to step S14.

[0033] Calculate the pheromone concentration value of the final current value vector:

[0034] , ;

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

[0036] 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 among the updated pheromone concentration values of the four tunable lasers and the pheromone concentration values calculated in step S13 as the optimal current value vector:

[0037] ;

[0038] 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。

[0039] For example, step S13 calculates the pheromone concentration value of the fifth tunable laser. Prior to this, the pheromone concentration values of the first, second, third, and fourth tunable lasers have been calculated. When k=1, it means that the evaporation rate P is used to update the pheromone concentration value of the first tunable laser. The rest are similar and will not be repeated here.

[0040] In this way, the pheromone concentration values of the five tunable lasers can be obtained, and the current value vector corresponding to the tunable laser with the largest pheromone concentration value is selected as the optimal current value vector P max , acting on step S12.

[0041] Step 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.

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

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

[0044] The fitting formula is:

[0045] ;

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

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

[0048] For example, the 7 current values corresponding to the 7 wavelength selection areas in the final current value vector obtained in step S13 are x1, x2, x3, x4, x5, x6 and x7. Taking the optimization process of the current value x1 as an example, the current value x1 is first jittered 7 times within a preset jitter range (for example, plus or minus 2 mA) to obtain x 11 、x 12 、x 13 、x 14 、x 15 、x 16 、x 17 These 7 current values and their corresponding optical powers. Fit a quadratic curve to the obtained current values and optical powers. The horizontal axis of the quadratic curve is the current value and the vertical axis is the optical power. Obtain the target current value x corresponding to the maximum optical power from the quadratic curve g , if x g If the current value x1 is equal to x1, the current value x1 is used as the optimal current value for the wavelength selection area. If they are not equal, the target current value x1 is used. g Replace the current value x1 and repeat the above steps until the optimal current value of the wavelength selection area is obtained.

[0049] Step S14 - 4 : Repeat steps S14 - 1 to S14 - 3 until the optimization of the current values of the seven 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 seven wavelength selection zones in the final value vector are optimized separately by a binary fitting optimization algorithm, that is, the current value that maximizes the optical power of the tunable laser is found within the preset jitter range of the current value of the wavelength selection zone, and is used as the optimal current value of the wavelength selection zone, so that the initial wavelength finally obtained can not only meet the wavelength error condition of the tunable laser, but also ensure that the optical power of the tunable laser is optimal.

[0051] Throughout step S1, based on the wavelength error condition, a particle swarm algorithm is used to find the value vector corresponding to the optimal current value of the wavelength selection zone, allowing accurate calibration of the initial wavelengths of different tunable lasers. During this process, the ant colony algorithm is used to further optimize and adjust the current value of the wavelength selection zone of the tunable laser, combining the optimal current values of the wavelength selection zones corresponding to the five most recently calibrated tunable lasers. This improves the robustness of the initial wavelength calibration and further ensures its reliability.

[0052] Step S2: For the tunable laser that has completed initial wavelength calibration, linear interpolation is performed on 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.

[0053] Specifically, the current values of the eight waveguide arms at the initial wavelength are adjusted by a fixed amount. These current values correspond to the optimal current values of the seven wavelength-selective zones and the current value of the one phase-control zone (CP). The current values of the eight waveguide arms are then optimized using a quadratic fitting algorithm. This yields a set of optimized current values (i.e., the current values of the eight waveguide arms) and their corresponding wavelengths. Through repeated optimization, multiple sets of current values and corresponding wavelengths are ultimately obtained.

[0054] By fitting the current value and the corresponding wavelength of each light guide arm respectively, eight current-wavelength curves corresponding to the eight light guide arms can be obtained, that is, the phase shift curves of the initial wavelength.

[0055] Perform linear interpolation on the phase shift curve of the initial wavelength 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 7 wavelength selection areas and the current value of the phase control area.

[0057] Step S3: The wavelength selection zone current and the phase control zone current of the tunable laser are respectively set to the current value of the wavelength selection zone and the current value of the phase control zone corresponding to the protocol wavelength, so that the tunable laser outputs the protocol wavelength; the proportional integral differential control algorithm is used to adjust the TEC1 temperature according to the current ambient temperature, so that the current actual wavelength of the tunable laser is locked 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 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 the 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:

[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's worth noting that the numerator, "I1 - I2," of the S-parameter calculation formula represents the difference between the transmitted and reflected laser intensities, a difference that is linearly related to wavelength shift. The denominator, "I1 + I2," represents the total light intensity and is used to eliminate the effects of tunable laser output power fluctuations on the S-parameters. For example, when power fluctuations cause I1 and I2 to increase and decrease synchronously, the ratio, S, of the numerator and denominator remains unchanged, reflecting only the wavelength shift. Therefore, S-parameters can be used to monitor output wavelength shifts.

[0063] Step 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:

[0064] ;

[0065] 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.

[0066] In the process from step S32 to step S33, the S parameters of the tunable laser under normal temperature, high temperature and low temperature environments are calculated respectively, that is, the optimal S parameters that meet the wavelength error conditions at different ambient temperatures, so that the optimal S parameters of the tunable laser under the current ambient temperature are calculated in combination with the current ambient temperature and the optimal S parameters, that is, the S parameter correction value. The optimal S parameters under the current ambient temperature can be accurately calculated, laying the foundation for the subsequent precise adjustment of the TEC1 temperature.

[0067] Step 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.

[0068] Step S35: Calculate 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:

[0069] , ;

[0070] Among them, u k Indicates the temperature adjustment value of TEC1, which is also the kth PID adjustment result; K p Indicates proportional gain; K i Indicates 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 Indicates the parameter difference after the k-2th PID adjustment; e jIndicates the parameter difference after the jth PID adjustment; S c,k-1 Indicates the S parameter corresponding to the current actual wavelength after the k-1th PID adjustment.

[0071] Step S36: Adjust the temperature of TEC1 based on the TEC1 temperature adjustment value to maintain the S parameter value within the target range around the S parameter correction value, thereby locking the current actual wavelength within the target range around the agreed wavelength:

[0072] ;

[0073] in, Indicates the adjusted TEC1 temperature; Indicates the temperature of TEC1 before adjustment.

[0074] Specifically, adjusting the temperature of the TEC1 controls the temperature of the laser chip, and thus the wavelength output of the tunable laser. Wavelength shifts can be monitored using S-parameters. Therefore, during the adjustment process, maintaining the S-parameter values within the target range around the S-parameter calibration values locks the current actual wavelength within the target range around the agreed-upon wavelength.

[0075] In this embodiment, a particle swarm-ant colony hybrid algorithm is used to find the current value in the wavelength selection zone that satisfies the wavelength error condition. This allows the determination of the optimal current value in the wavelength selection zone required for the output wavelength of the tunable laser to achieve the actual agreed wavelength for different tunable lasers. This allows for targeted calibration of the initial wavelengths of different tunable lasers, greatly improving the reliability of initial wavelength calibration. On this basis, the agreed wavelength can be accurately calibrated based on the initial wavelength. Simultaneously, the TEC1 temperature is adjusted according to the current ambient temperature using a proportional-integral-differential control algorithm. This allows for real-time correction of the TEC1 temperature based on the current ambient temperature, thereby locking the current actual wavelength of the tunable laser within the target range around the agreed wavelength in a temperature-fluctuating operating environment, ensuring stable output of the tunable laser wavelength.

[0076] The serial numbers of the above embodiments of the present invention are for description only and do not represent the advantages or disadvantages of the embodiments.

[0077] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

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; 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: 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; 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 through 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.

3. The method for initial wavelength calibration and wavelength locking of a tunable laser according to claim 2, 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 among 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。 4. The method for initial wavelength calibration and wavelength locking of a tunable laser according to claim 2, 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, fitting 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, repeatedly executing S14-1 to S14-3 until the optimization of the current values of the seven wavelength selection regions is completed, thereby obtaining the initial wavelength of the tunable laser.

5. 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.

Images