A wavelength tuning method based on an external cavity double micro-ring laser

Abstract

The present application relates to the field of optical communication technology, disclose a kind of wavelength tuning method based on external cavity double micro-ring laser, it solves the technical problems such as the large data quantity, long time consumption, easy to miss target wavelength and unable to simultaneously optimize side mode rejection ratio and line width etc. core performance index of existing traversal method to carry out wavelength tuning.The present application realizes the accurate analysis of the relationship between driving voltage and wavelength by establishing physical model and quadratic fitting relationship, avoids full-range current scanning;Utilize vernier effect under the wavelength selection mechanism of double micro-ring resonance peak alignment, ensure that output wavelength is accurately locked to protocol wavelength, performance is superior to approximate lookup table method;Through theoretical derivation and experimental calibration, the driving voltage corresponding to any reference wavelength can be predicted, which adapts to the individual differences of different micro-rings and realizes personalized rapid tuning;A large number of trial-and-error processes are transferred to simulation and theoretical calculation, which reduces the occupation and energy consumption of physical test equipment and improves production efficiency and production line resource utilization.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, and in particular to a wavelength tuning method based on an external cavity dual microring laser. Background Technology

[0002] Tunable lasers, with their dynamic wavelength allocation capabilities, improve bandwidth utilization and configuration flexibility in optical communication systems, and their performance has become a key factor restricting the efficiency of high-speed optical interconnects in data centers.

[0003] In existing technologies, references 1-3 specifically disclose the research and verification of wavelength tuning of distributed Bragg reflection (DBR) lasers using the ergodic method. The ergodic method is also the most widely used wavelength tuning method for tunable lasers in existing technologies. The classic experimental structure of the ergodic method is as follows: Figure 1 As shown, the DBR is divided into four functional segments, each controlled by a separate current channel of the laser diode controller. In the experiment, the temperature of the DBR is first stabilized at the set value by controlling the TEC of the laser diode controller, and then the current of the gain segment of channel three is... To maintain a constant current, the computer sends instructions to the laser diode controller via the GPIB bus, sequentially changing the post-sampling grating current of channel one within a certain range. Phase segment current of channel two Channel 4 front sampling grating current Iterate through all possible combinations of currents, for each group ( , , The corresponding output wavelength is measured using a spectral analyzer, and all current combination-output wavelength data are compiled into a lookup table. When a specific target wavelength is needed later, simply look up the corresponding value in the table. , , The current combination can be set directly without needing to scan again.

[0004] Reference 1: Title: Research on Control of Monolithic Integrated Tunable Semiconductor Laser, Author: Lü Hui; Reference 2: Title: Research on Characteristics of Tunable Integrated Devices Based on SGDBR Laser, Author: Shu Tan; Reference 3: Title: Research on Multi-Segment Tunable Semiconductor Laser, Author: Zhou Hongwei.

[0005] Specific wavelength tuning, such as Figure 2 As shown, the steps are as follows:

[0006] Step 1: Perform a current scan of 0 to 40 mA with a step size of 0.5 mA on the front and rear sampling grating sections to generate an initial current-wavelength lookup table.

[0007] Step 2: Filter the data in the initial current-wavelength lookup table by side-mode rejection ratio (SMSR). If the SMSR > 30dB, retain it; otherwise, remove it. If the value is 30dB, delete it and keep only the data points with an SMSR greater than 30dB.

[0008] Step 3: Categorize the retained data (sort by wavelength), retaining the data points with the highest SMSR among the scan points of the same wavelength to optimize data reliability;

[0009] Step 4: Verify the wavelength deviation of the data points based on the channel wavelength specified by the International Telecommunication Union (ITU). Check whether it meets the ITU's maximum channel wavelength deviation requirement. If it does, retain the data points and generate the final current-wavelength lookup table. If it does not meet the requirement, enter a phase segment current scan with a range of 0 to 8 mA and a step size of 0.2 mA to compensate for the wavelength deviation. Check the compensated data points again to see if they meet the ITU's maximum channel wavelength deviation requirement. If they do not meet the requirement, delete the data points. If they do meet the requirement, generate the final current-wavelength lookup table for the static wavelength control module to call to achieve precise wavelength locking.

[0010] Analysis of the wavelength tuning method using the ergodic approach reveals several problems: it requires traversing all possible current combinations, resulting in a massive amount of current combination data and extremely long traversal time, severely restricting production efficiency; if the current tuning step size is set too large, incomplete coverage of the target wavelength may occur, and some channel wavelengths specified by the ITU may not be able to achieve precise wavelength locking; the generated final current-wavelength lookup table is only an approximate correspondence, with significant limitations in optimizing core indicators such as side-mode rejection ratio and linewidth, failing to achieve optimal device performance. Summary of the Invention

[0011] The purpose of this invention is to address the technical problems of existing ergodic methods for wavelength tuning, such as large data volume, long time consumption, easy omission of target wavelength, and inability to simultaneously optimize core performance indicators such as side-mode suppression ratio and linewidth, by providing a wavelength tuning method based on an external cavity dual-micro-ring laser.

[0012] To achieve the above-mentioned objectives, the embodiments of the present invention provide the following technical solutions:

[0013] A wavelength tuning method based on an external cavity dual-microring laser includes the following sub-steps:

[0014] The optical path difference is obtained by using the thermo-optic coefficient and the thermal expansion coefficient expression. The initial length, thermo-optic coefficient, thermal expansion coefficient and initial refractive index of the microring material are then input to simulate the optical path difference and the temperature change of the microring material, and the proportionality coefficient is obtained.

[0015] The free spectral range is calculated, and the change in the free spectral range is obtained by using the free spectral range and the initial free spectral range. The change in the free spectral range and the temperature change of the microring material are used for simulation to eliminate the influence of the temperature change of the microring material on the change in the free spectral range.

[0016] By analyzing the interference pattern of light within the microring, the position of the spectral peak is determined, and the linear relationship between the wavelength shift of the spectral peak and the temperature change of the microring material is determined using the position of the spectral peak.

[0017] By applying Joule's law and the laws of heat transfer, a fitting relationship between temperature and driving voltage for microring materials was established.

[0018] By combining the fitting relationship between the peak wavelength shift and the temperature and driving voltage of the microring material, the peak wavelength expression is obtained. Whenever the reference wavelength of the microring is changed, the driving voltage relationship corresponding to different microring peak wavelengths is derived using the peak wavelength expression theory.

[0019] By correlating the peak wavelength with the driving voltage through a quadratic fitting, the reference wavelength obtained by the fitting is discarded, and the relationship between the peak wavelength and the driving voltage is obtained. The optimal peak wavelength is obtained by using the difference between the protocol wavelength and the peak wavelength group. The driving voltage is determined by the reference wavelength corresponding to the optimal peak wavelength and the reference wavelength.

[0020] To address the technical problems of existing ergonomic wavelength tuning methods, such as massive data volume, long processing time, easy omission of target wavelengths, and inability to simultaneously consider core performance indicators like side-mode suppression ratio and linewidth, this application obtains the optical path difference and proportionality coefficient through the thermo-optic coefficient and thermal expansion coefficient of the microring material, eliminating the influence of temperature changes on the change in the free spectral range. Utilizing the linear relationship between peak wavelength shift and temperature, combined with the quadratic fitting relationship between temperature and driving voltage, a theoretical correlation model between peak wavelength and driving voltage is derived. Then, a peak wavelength-driving voltage relationship is established through quadratic fitting. The optimal peak wavelength and its reference wavelength are determined using the difference between the agreed wavelength and the peak wavelength group, thereby calculating the target driving voltage for each of the two microrings. This solves the problems of traditional ergonomic methods requiring massive current combination trial and error, long processing time, and easy omission of channel wavelengths. Simultaneously, by utilizing the wavelength selection mechanism of dual-microring resonant peak alignment under the vernier effect, high side-mode suppression ratio and narrow linewidth are ensured while accurately locking the agreed wavelength, avoiding the performance limitations of approximate lookup tables.

[0021] To address the technical problems of slow convergence speed, reliance on manual experience, and long equipment occupation time in existing wavelength tuning methods, this application establishes an analytical model of wavelength and driving voltage through theoretical derivation. The parameter optimization process is transferred from physical trial and error to simulation and quadratic fitting. The optimal driving voltage is quickly obtained by using difference screening and reference wavelength mapping. This solves the problems of blind trial and error, inconsistent convergence, and occupation of expensive test equipment in the experience-based tuning method. It realizes intelligent guidance and rapid convergence of the tuning process, and significantly reduces physical test time and resource consumption.

[0022] Compared with existing technologies, the beneficial effects of this invention are as follows: By establishing a physical model based on thermo-optical effects and thermal expansion, and a quadratic fitting relationship, accurate analysis of the relationship between driving voltage and wavelength is achieved, avoiding full-range current scanning and shortening wavelength tuning time from hours to seconds; by utilizing the wavelength selection mechanism of dual micro-ring resonant peak alignment under the vernier effect, the output wavelength is ensured to be accurately locked to the protocol wavelength, while automatically obtaining high side-mode rejection ratio and narrow linewidth, outperforming the approximate lookup table method; the driving voltage corresponding to any reference wavelength can be predicted through theoretical derivation and a small number of experimental calibrations, adapting to the individual differences of different micro-rings and achieving personalized rapid tuning; a large amount of trial and error process is transferred to simulation and theoretical calculation, reducing the occupation and energy consumption of physical testing equipment, and improving production efficiency and production line resource utilization.

[0023] Furthermore, a wavelength tuning method based on an external cavity dual-microring laser, wherein the optical path difference is obtained through the thermo-optic coefficient expression and the thermal expansion coefficient expression, and the initial length, thermo-optic coefficient, thermal expansion coefficient and initial refractive index of the microring material are input, and the optical path difference and the temperature change of the microring material are simulated to obtain the scaling factor includes the following sub-steps:

[0024] The expression for the thermo-optic coefficient is obtained by using the temperature and refractive index of the microring material:

[0025] The expression for the coefficient of thermal expansion is obtained by considering the initial length, length, and temperature of the microring material:

[0026] When the temperature of the microring material changes At that time, the changes in refractive index and length of the microring material are obtained through the expressions for the coefficient of thermal expansion and the thermo-optic coefficient;

[0027] When the temperature of the microring material changes At that time, the refractive index and length of the microring material are obtained by measuring the changes in refractive index and length of the microring material;

[0028] The initial optical path is obtained by using the initial refractive index and length of the microring material; the optical path difference is obtained by using the initial optical path and the initial optical path.

[0029] By incorporating the initial length, thermo-optic coefficient, thermal expansion coefficient, and initial refractive index of the microring material, the optical path difference and the temperature change of the microring material are simulated. The proportionality coefficient is obtained through the linear relationship between the optical path difference and the temperature change of the microring material.

[0030] In the aforementioned solutions, existing technologies typically only consider a single thermo-optical effect or a simple linear approximation when obtaining the proportionality coefficient of the optical path difference and temperature change of microring materials. They neglect the dual contribution of thermal expansion to the optical path (i.e., simultaneous changes in refractive index and length), and fail to simulate and verify the nonlinear characteristics of material parameters within the actual operating temperature range. This results in a large error in the obtained proportionality coefficient, failing to accurately describe the true relationship between the optical path difference and temperature. Consequently, cumulative deviations occur in subsequent steps such as calculating the wavelength shift of the spectral peak and deriving the driving voltage relationship, severely restricting the accuracy and reliability of wavelength tuning. This application establishes theoretical expressions for the thermo-optical coefficient and the coefficient of thermal expansion, quantitatively obtaining the changes in refractive index and length of the microring material when the temperature changes. The optical path difference is then calculated by combining the initial refractive index and initial length. Furthermore, simulations are performed on the optical path difference and temperature change within the actual operating temperature range (e.g., below 100℃). The accurate proportionality coefficient is obtained using the linear relationship within this range, solving the technical problem of inaccurate proportionality coefficients caused by neglecting the thermal expansion effect or using a global linear approximation in traditional methods. This application uses a dual mechanism of thermo-optics and thermal expansion for modeling, and combines initial parameters with interval linearization simulation processing. This enables the obtained scaling factor to accurately reflect the actual optical path change law of the micro-ring material during thermal tuning. This provides a solid and reliable physical basis for the subsequent elimination of changes in the free spectral range, the establishment of the linear relationship of spectral peak wavelength shift, and the construction of driving voltage-wavelength analysis. As a result, it significantly improves the modeling accuracy of the entire wavelength tuning method and the locking accuracy of the final output wavelength.

[0031] Furthermore, a wavelength tuning method based on an external cavity dual-microring laser, wherein the optical path difference is expressed as:

[0032] ;

[0033] in, The refractive index of the microring material, The length of the microring material, The initial refractive index of the microring material. The initial length of the microring material. This represents the temperature change of the microring material. Thermo-optic coefficient, is the coefficient of thermal expansion.

[0034] In the aforementioned schemes, existing technologies, when establishing the quantitative relationship between the optical path difference of a microring and the temperature change, typically employ only a single physical effect (such as considering only the refractive index change caused by the thermo-optic effect) or a simple linear superposition model. This neglects the actual change in the microring length due to thermal expansion and the coupling effect between refractive index change and length change. Consequently, the optical path difference expression cannot fully reflect the true optical path evolution of the microring material during temperature tuning. Furthermore, traditional models often directly assume an ideal linear relationship between the optical path difference and the temperature change, failing to consider the potential impact of second-order cross-coupling terms on accuracy. This results in inherent deviations in the subsequently extracted proportionality coefficients, leading to accumulated errors in a series of steps, such as calculating the spectral peak wavelength shift and deriving the driving voltage-wavelength relationship, severely restricting the final locking accuracy of wavelength tuning. This application, by introducing an optical path difference expression that simultaneously includes both the thermo-optic coefficient and the thermal expansion coefficient, fully preserves the first-order and second-order cross-coupling terms related to temperature change. This accurately characterizes the combined contribution of refractive index change and length change to the optical path, solving the technical problem of inaccurate proportionality coefficients caused by neglecting the thermal expansion effect or making only linear approximations in traditional models. This application adopts the above-mentioned optical path difference expression containing first-order and second-order terms, and combines it with simulation verification of the actual working temperature range, making the extraction of the linear proportional coefficient between optical path difference and temperature change more accurate and reliable.

[0035] Furthermore, in a wavelength tuning method based on an external cavity dual-microring laser, the proportionality coefficient is expressed as follows:

[0036] ;

[0037] in, This is the proportionality coefficient. For optical path difference, This represents the temperature change of the microring material.

[0038] In the aforementioned schemes, existing technologies typically use a first-order approximation from theoretical derivation to directly assess the actual contribution of the optical path difference to the temperature change when determining the proportionality coefficient of the microring material. Furthermore, these methods fail to perform simulation verification for the actual operating temperature range of specific microring materials (such as silicon nitride), leading to inherent errors in the proportionality coefficient values. Simultaneously, the values ​​of thermo-optic coefficients and thermal expansion coefficients vary significantly across different literature and methods. Directly substituting these values ​​into theoretical formulas fails to accurately reflect the thermal response characteristics of the actual device, resulting in cumulative deviations in subsequent calculations of spectral peak wavelength shift and derivation of the driving voltage-wavelength relationship, severely impacting the accuracy and reliability of wavelength tuning. This application addresses this issue by employing a proportionality coefficient expression combined with simulation of the optical path difference and temperature change within an actual operating temperature range (e.g., below 100℃). Utilizing the significant linear relationship between the optical path difference and material temperature within this range, an accurate proportionality coefficient is directly extracted from the simulation data. This solves the technical problem of inaccurate proportionality coefficients caused by neglecting second-order terms and differences in material parameters in traditional theoretical approximation methods. This application establishes the determination of the scaling factor based on the linear fitting between the simulation and the measured temperature range, rather than simply relying on idealized theoretical formulas. This allows the obtained scaling factor to accurately reflect the optical path-temperature response characteristics of a specific microring material during the actual thermal tuning process, thereby significantly improving the modeling accuracy of the entire wavelength tuning method and the locking reliability of the final output wavelength.

[0039] Furthermore, a wavelength tuning method based on an external cavity dual-microring laser, wherein the calculation of the free spectral range, obtaining the change in free spectral range through the free spectral range and the initial free spectral range, and performing simulation using the change in free spectral range and the temperature change of the microring material, and eliminating the influence of the temperature change of the microring material on the change in free spectral range, includes the following sub-steps:

[0040] A free spectral range can be obtained by considering the wavelength of light waves, the refractive index of the microring material, and its length.

[0041] When the temperature of the microring material changes At that time, the change in free spectral range is obtained by comparing the free spectral range with the initial free spectral range;

[0042] By incorporating the initial length and initial refractive index of the microring material, the wavelength of the light wave, the optical path difference, and the scaling factor, simulations were performed on the changes in the free spectral range and the temperature changes of the microring material, thus eliminating the influence of the temperature changes of the microring material on the changes in the free spectral range.

[0043] In the above-mentioned schemes, existing technologies, when establishing micro-ring temperature tuning models, typically assume that the free spectral range (FSR) remains constant during temperature changes, or simply use theoretical formulas for estimation, ignoring the actual impact of changes in the micro-ring refractive index and length caused by temperature changes on the amount of FSR change. Even if some methods take into account the change in FSR, they often directly use an approximate linear model without combining the obtained optical path difference and scaling factor for targeted simulation and quantitative evaluation. This makes it impossible to accurately determine the actual magnitude and negligibility of the FSR change throughout the entire temperature tuning range, which in turn introduces unnecessary error terms into the subsequent calculation of spectral peak wavelength shift and the derivation of the driving voltage-wavelength relationship, reducing the overall accuracy of the wavelength tuning model.

[0044] This application first obtains the free spectral range using the wavelength of light, the refractive index and length of the microring material, then combines the changes in refractive index and length with temperature changes to obtain the change in the free spectral range. Finally, based on the initial length, initial refractive index, wavelength of light, the calculated optical path difference and the proportionality coefficient of the microring material, the change in the free spectral range is simulated to quantitatively verify the magnitude of the change in the free spectral range within the actual operating temperature range of the microring material (e.g., below 100℃) (e.g., only about 1.5 pm). This clearly eliminates the influence of the temperature change of the microring material on the change in the free spectral range, solving the technical problem of model error introduced by traditional methods due to ignoring or incorrectly estimating FSR changes. This application incorporates the simulation evaluation of the change in free spectral range into the wavelength tuning modeling process. It uses the calibrated optical path difference and scaling factor for accurate calculation and visualization verification. From a physical mechanism perspective, it confirms that the change in free spectral range is negligible within the effective tuning range. This allows the subsequent linear relationship between peak wavelength shift and temperature change, as well as the establishment of driving voltage-wavelength resolution, to be free from interference caused by FSR fluctuations. This significantly improves the simplicity and accuracy of the wavelength tuning model, ensuring that the locking of the final output wavelength is more stable and reliable.

[0045] Furthermore, a wavelength tuning method based on an external cavity dual-microring laser, wherein establishing a fitting relationship between the temperature of the microring material and the driving voltage using Joule's law and heat transfer principles includes the following sub-steps:

[0046] The heating power of the microrings is obtained through Joule's law;

[0047] The heat dissipation power of the micro-ring is obtained by understanding the laws of heat transfer;

[0048] When the heat dissipation power of the microring is equal to the heating power of the microring, the temperature of the microring material is determined.

[0049] By excluding the resistance value that varies with the temperature of the microring material, the relationship between the temperature of the microring material and the driving voltage is obtained;

[0050] The relationship between the temperature and driving voltage of the microring material is fitted to obtain the fitting relationship between the temperature and driving voltage of the microring material.

[0051] Furthermore, in a wavelength tuning method based on an external cavity dual-microring laser, the relationship between the temperature of the microring material and the driving voltage is expressed as:

[0052] ;

[0053] in, The temperature of the microring material, For driving voltage, This is the nominal resistance value of the heating resistor. For heat transfer and electrical conductivity, The ambient temperature.

[0054] In the above-mentioned schemes, existing technologies, when establishing the fitting relationship between temperature and driving voltage of microring materials, usually directly assume that temperature and driving voltage have a simple linear relationship or only perform idealized calculations based on Joule's law. They ignore the thermal balance mechanism of the microring during actual operation (i.e., the dynamic balance between heating power and heat dissipation power), and do not consider the combined influence of the change of heating resistor value with temperature and heat dissipation conditions (heat conduction, heat convection, and heat radiation) on the temperature-voltage mapping relationship. This results in a large error in the established temperature-voltage model, which cannot accurately reflect the thermal response characteristics of the real device under different ambient temperatures and driving conditions. Consequently, the subsequent derivation of the peak wavelength-driving voltage relationship will be biased, seriously affecting the accuracy and reliability of wavelength tuning. This application establishes the relationship between heating power and driving voltage using Joule's law, and simultaneously establishes the relationship between heat dissipation power, microring material temperature, and ambient temperature using heat transfer laws. The temperature of the microring material is determined using thermal equilibrium conditions. Furthermore, the influence of resistance changes with temperature is eliminated (resistance changes are negligible within a 100℃ range), resulting in a simplified temperature-driving voltage relationship. Finally, a second-order fitting is performed on this relationship to obtain a fitted relationship. This solves the technical problem of inaccurate temperature-voltage mapping caused by neglecting the thermal equilibrium mechanism, heat dissipation loss, and resistance-temperature characteristics in traditional models. By fully introducing a heating-heat dissipation dual-mechanism model and combining the thermal equilibrium equation with second-order fitting, this application enables the established fitted relationship between microring material temperature and driving voltage to accurately reflect the nonlinear characteristics of the actual thermal tuning process. This provides accurate intermediate physical quantities for the subsequent theoretical derivation and experimental calibration of the peak wavelength-driving voltage relationship, thereby significantly improving the modeling accuracy of the entire wavelength tuning method and the reliability of the final output wavelength lock.

[0055] Furthermore, a wavelength tuning method based on an external cavity dual-microring laser, wherein the expression for the spectral peak wavelength is:

[0056] ;

[0057] in, The wavelength of the spectral peak. For driving voltage, This is the proportionality coefficient. The coefficient of the quadratic term, The coefficient of the linear term, The order of the oscillation spectrum peak. The reference wavelength is used.

[0058] In the above-mentioned schemes, existing technologies, when theoretically deriving the relationship between peak wavelength and driving voltage, usually treat the peak wavelength shift as a simple linear relationship with the driving voltage, or simply interpolate and look up tables using experimental discrete points. They do not fully utilize the established temperature-driving voltage quadratic fitting relationship and the linear relationship between peak wavelength shift and temperature for joint derivation. At the same time, traditional methods often ignore the fixing effect of the order of the oscillating peak on the coefficients of the quadratic and linear terms, and fail to recognize that the peak wavelength-driving voltage relationship of different microrings can be predicted by changing the value of the reference wavelength. As a result, the obtained relationship model is only applicable to specific peaks of specific microrings, lacking universality and transferability. It requires a large number of calibration experiments for each microring and each peak, which is time-consuming, laborious, and difficult to adapt to individual differences in production. This application derives the expression for the relationship between spectral peak wavelength shift and driving voltage by jointly deriving a quadratic fitting relationship. The proportionality coefficient is obtained through simulation. Simultaneously, the order of the oscillating peak is fixed to determine the coefficients of the quadratic and linear terms. By changing the reference wavelength of the microring, the driving voltage relationship corresponding to different microring spectral peak wavelengths can be predicted. This solves the technical problems of poor model generalization ability and huge calibration workload caused by the lack of a combined physical model and fixed-order strategy in traditional methods. Furthermore, this application cascades the linear relationship between spectral peak wavelength shift and temperature, and the quadratic fitting relationship between temperature and driving voltage, combined with a parameterized modeling strategy of fixed order and variable reference wavelength. This allows the obtained spectral peak wavelength-driving voltage relationship model to adapt to the tuning characteristics of different microrings and different spectral peaks simply by adjusting parameters, significantly reducing the experimental calibration sample size while ensuring the prediction accuracy of the model over a wide wavelength range (prediction error less than 30 pm in the example). This lays an efficient and accurate model foundation for quickly determining the optimal driving voltage through difference screening.

[0059] Furthermore, a wavelength tuning method based on an external cavity dual-microring laser, wherein the driving voltage is determined by matching the optimal spectral peak wavelength with a reference wavelength and using the optimal spectral peak wavelength and the reference wavelength as follows:

[0060] By fixing the driving voltage of one micro-ring and scanning the driving voltage of another micro-ring, the discrete spectral peaks at the coincident resonance are collected to obtain the spectral peak wavelengths and integrate them to obtain a spectral peak wavelength group.

[0061] The peak wavelength is then fitted twice with the corresponding driving voltage, and the reference wavelength is discarded to obtain the peak wavelength. -Drive voltage relation ;

[0062] Input the protocol wavelength, calculate the difference between the protocol wavelength and the wavelengths of each spectral peak using the spectral peak wavelength group, and filter out the smallest difference that is greater than zero. Through the minimum difference Determine the optimal spectral peak wavelength and use the optimal spectral peak wavelength to correspond to the reference wavelength;

[0063] Joint peak wavelength-driving voltage relationship and minimum difference The target driving voltage of each of the two microrings is obtained. The target driving voltage is applied to the two microrings through the heater, and the optimal spectral peak wavelength is tuned to the protocol wavelength. The protocol wavelength optical signal is output by utilizing the vernier effect.

[0064] In the above-mentioned schemes, existing technologies (such as the ergodic method) typically need to traverse all possible current (or voltage) combinations of the two microrings to determine the target driving voltage of each microring in order to achieve the protocol wavelength output. They need to measure the output wavelength under each combination and search from massive amounts of data for driving conditions that can align the resonant peaks of the two microrings and lock them to the protocol wavelength. This results in a huge amount of data and extremely long processing time. Furthermore, if the step size is not set properly, the target wavelength may be missed. At the same time, the ergodic method can only establish a discrete current-wavelength approximation lookup table and cannot directly use the analytical relationship between the reference wavelength and the driving voltage for fast solution. This makes the wavelength tuning process heavily dependent on exhaustive search, resulting in low production efficiency and difficulty in taking into account core performance indicators such as side-mode rejection ratio and linewidth. This application obtains discrete spectral peaks at coincident resonance by fixing the driving voltage of one microring and scanning the driving voltage of the other microring, and integrates them to obtain a set of spectral peak wavelengths. The spectral peak wavelengths are then fitted twice with their corresponding driving voltages, discarding the reference wavelength to obtain the relationship between spectral peak wavelength and driving voltage. After inputting the protocol wavelength, the difference between the protocol wavelength and each spectral peak wavelength is calculated using the spectral peak wavelength set. The smallest difference greater than zero is selected, and the optimal spectral peak wavelength and its corresponding reference wavelength are determined using this smallest difference. Finally, the target driving voltage for each of the two microrings is obtained by combining the spectral peak wavelength-driving voltage relationship and the smallest difference. The two microrings apply the target driving voltage through a heater, precisely tuning the optimal spectral peak wavelength to the protocol wavelength. The protocol wavelength optical signal is output using the vernier effect. This solves the technical problems of the ergonomic method, which suffers from extremely long time consumption due to exhaustive search, easy omission of channel wavelengths, and inability to simultaneously optimize core performance indicators. This application establishes an analytical model by acquiring only single-dimensional scan data through a fixed-scan strategy. It quickly determines the optimal driving voltage by using difference filtering and reference wavelength mapping, completely avoiding the massive combination trial and error caused by two-dimensional traversal, and reducing the wavelength tuning time from several hours to seconds. At the same time, the dual micro-ring resonant peak alignment mechanism based on the vernier effect ensures that the output wavelength is accurately locked to the protocol wavelength, automatically obtaining a high side-mode rejection ratio and narrow linewidth, which significantly improves the efficiency, accuracy and device performance of wavelength tuning. Attached Figure Description

[0065] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0066] Figure 1 This is a typical experimental structure diagram of the traversal method.

[0067] Figure 2 This is a flowchart for wavelength tuning.

[0068] Figure 3This is a schematic diagram of the vernier effect.

[0069] Figure 4 This is a flowchart of a wavelength tuning method based on an external cavity dual-microring laser.

[0070] Figure 5 The simulation diagram shows the optical path difference and temperature.

[0071] Figure 6 This is a partial simulation diagram of optical path difference and temperature.

[0072] Figure 7 Simulation diagrams showing the changes in the free spectral range and temperature.

[0073] Figure 8 A partial simulation plot showing the changes in the free spectral range and temperature.

[0074] Figure 9 A schematic diagram for calculating wavelength difference.

[0075] Figure 10 This is a schematic diagram of the micro-ring and reference wavelength sorting.

[0076] Figure 11 The simulation diagram shows the reference wavelength and driving voltage of the micro-ring.

[0077] Figure 12 The simulation diagram shows the shortest reference wavelength and driving voltage of the micro-ring.

[0078] Figure 13 This is a schematic diagram illustrating the prediction error of the shortest reference wavelength for a micro-ring.

[0079] Figure 14 The simulation diagram shows the longest reference wavelength and driving voltage of the micro-ring.

[0080] Figure 15 This is a schematic diagram illustrating the prediction error of the longest reference wavelength of the micro-ring.

[0081] Figure 16 This is a schematic diagram of the two reference wavelengths of the microring.

[0082] Figure 17 The simulation diagram shows the shortest reference wavelength and driving voltage of the micro-ring II.

[0083] Figure 18 This is a schematic diagram illustrating the prediction error of the shortest reference wavelength of the micro-ring II.

[0084] Figure 19 The simulation diagram shows the longest reference wavelength and driving voltage of the micro-ring II.

[0085] Figure 20 This is a schematic diagram illustrating the prediction error of the longest reference wavelength of the micro-ring. Detailed Implementation

[0086] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0087] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance, or suggesting any such actual relationship or order between these entities or operations. Additionally, the terms "connected," "linked," etc., can refer to a direct connection between elements or an indirect connection via other elements.

[0088] Example 1: A wavelength tuning method based on an external cavity dual-microring laser

[0089] In existing technologies, whether it's a DBR or the external cavity dual-microring laser involved in this invention, the core principle of wavelength tuning is the vernier effect. For a DBR, the output wavelength must simultaneously satisfy the resonance conditions of the front and rear sampling gratings. Wavelengths that do not satisfy these dual resonance conditions will be suppressed. Therefore, the equivalent refractive index of the grating can be changed by tuning the grating current, thereby adjusting the resonance conditions and achieving continuous tuning of the output wavelength. Similarly, the output wavelength of an external cavity dual-microring tunable laser must also simultaneously satisfy the resonance conditions of the two microring resonators. By tuning the refractive index or equivalent cavity length of the microrings, their respective resonance conditions can be changed. Based on the vernier effect wavelength selection mechanism, precise control of the output wavelength is ultimately achieved.

[0090] like Figure 3 As shown, the principle behind selecting the dual microrings is that the vernier effect is essentially the superposition and selection of two resonant spectra with slightly different periods, resulting in a composite resonant spectrum with a larger period. The frequency interval between adjacent resonant peaks of microring 1 is... The frequency interval between adjacent resonant peaks of microring 2 is The arrows represent resonant peaks. The vernier effect is only preserved and output in the dual microrings when the resonant peaks of microring 1 and microring 2 are exactly aligned; other wavelengths are suppressed. Most of the time, the resonant peaks of microring 1 and microring 2 are staggered and do not resonate simultaneously. Only at a few specific frequency points will the resonant peaks of the two microrings overlap and align. These overlapping arrows constitute the new resonant peaks of the dual microrings, meaning the frequency interval between adjacent resonant peaks of the dual microrings is... ,and The resonant peaks become sparse, thus enabling a wider tuning range and more precise wavelength selection.

[0091] This invention is achieved through the following technical solutions, such as... Figure 4 As shown, a wavelength tuning method based on an external cavity dual-microring laser includes the following steps:

[0092] S1: Obtain the optical path difference using the thermo-optic coefficient and thermal expansion coefficient expressions. Substitute the initial length, thermo-optic coefficient, thermal expansion coefficient, and initial refractive index of the microring material into the simulation to obtain the proportionality coefficient by simulating the optical path difference and the temperature change of the microring material.

[0093] It is important to note that the thermal effect has a dual mechanism for affecting the optical path length of the microring: first, the thermal effect affects the optical path length of the microring by changing the refractive index of the microring material; second, the thermal effect causes the length of the microring material to expand and contract with temperature, thereby changing the optical path length of the microring. Therefore, it is necessary to explore the relationship between the optical path length of the microring and temperature from the perspective of the dual mechanism.

[0094] Specifically, S1 includes the following sub-steps:

[0095] S11: Obtain the expression for the thermo-optic coefficient using the temperature and refractive index of the microring material:

[0096] ;

[0097] in, The refractive index of the microring material, The temperature of the microring material, The thermo-optic coefficient reflects the rate of change of the refractive index of the microring material with the temperature of the microring material.

[0098] In this embodiment, silicon nitride is used as the microring material, and the thermo-optic coefficient of silicon nitride is... Furthermore, the thermo-optical coefficient of silicon nitride is stable at temperatures between 20℃ and 100℃. Therefore, the relationship between the optical path length of the microring and the temperature of silicon nitride is established below 100℃.

[0099] S12: Obtain the expression for the coefficient of thermal expansion using the initial length, length, and temperature of the microring material:

[0100] ;

[0101] in, The coefficient of thermal expansion is The initial length of the microring material. The length of the microring material is given by the coefficient of thermal expansion, which reflects the rate of change of the length of the microring material with the temperature of the microring material.

[0102] In the embodiments, the coefficient of thermal expansion of silicon nitride is also affected by the crystal arrangement of silicon nitride, so the value of silicon nitride is not a constant. Silicon nitride usually exists in the following forms: and , The coefficient of thermal expansion is , The coefficient of thermal expansion is .

[0103] S13: When the temperature of the microring material changes At that time, the changes in refractive index and length of the microring material are obtained through the expressions for the coefficient of thermal expansion and the thermo-optical coefficient. The expressions are:

[0104] ;

[0105] in, This represents the change in refractive index of the microring material. This represents the change in length of the microring material. This represents the temperature change of the microring material.

[0106] S14: When the temperature of the microring material changes At that time, the refractive index and length of the microring material are obtained by measuring the change in refractive index and the change in length, and the expression is:

[0107] ;

[0108] in, The initial refractive index of the microring material. Temperature changes in microring materials At that time, the refractive index of the microring material, Temperature changes in microring materials At that time, the length of the microring material;

[0109] S15: The initial optical path is obtained from the initial refractive index and length of the microring material; the optical path length is obtained from the initial refractive index and length of the microring material; and the optical path difference is obtained from the optical path length and the initial optical path length. The expression is as follows:

[0110] ;

[0111] in, The optical path difference reflects the temperature change of the microring material. The difference between the optical path length of the microring material and the initial optical path length of the microring material;

[0112] It is important to note that For the optical path length of the microring material, The initial optical path length of the microring material is given, and the initial temperature is the ambient temperature. Both the initial optical path length and the initial refractive index are obtained at the initial temperature.

[0113] S16: By incorporating the initial length, thermo-optic coefficient, thermal expansion coefficient, and initial refractive index of the microring material, the optical path difference and the temperature change of the microring material are simulated. The proportionality coefficient is obtained through the linear relationship between the optical path difference and the temperature change of the microring material, expressed as:

[0114] ;

[0115] in, This is the proportionality coefficient.

[0116] In this embodiment, according to the expression in S15, the optical path difference is a function of the temperature change of silicon nitride. However, the relationship between the optical path difference and the temperature change of silicon nitride is not linear. Therefore, by substituting the specific values ​​of the thermo-optic coefficient, thermal expansion coefficient, initial length, and initial refractive index of silicon nitride, a simulation is performed, and the expression becomes:

[0117] ;

[0118] It should be noted that the thermo-optical coefficient of silicon nitride is [value missing]. The coefficient of thermal expansion of silicon nitride is taken as . The initial length of silicon nitride is The initial refractive index of silicon nitride is 2.5.

[0119] Simulation of optical path difference, such as Figure 5 As shown, when the temperature change of silicon nitride is within At this time, the optical path difference exhibits a significant nonlinear change, and the relationship between the optical path difference of the microring and the temperature of silicon nitride is established below 100℃, where the thermo-optical coefficient stabilizes. Figure 6 As shown, when the temperature change of silicon nitride is below 100℃, the optical path difference exhibits a clear linear trend. Therefore, the optical path difference and the temperature change of silicon nitride can be approximated by a linear model. ,at this time .

[0120] S2: Calculate the free spectral range, obtain the change in free spectral range by using the free spectral range and the initial free spectral range, and use the change in free spectral range and the temperature change of the microring material for simulation to eliminate the influence of the temperature change of the microring material on the change in free spectral range.

[0121] S21: The free spectral range (i.e., the frequency interval between adjacent resonance peaks) is obtained by using the wavelength of the light wave, the refractive index of the microring material, and its length. The expression is:

[0122] ;

[0123] in, For the free spectral range, The wavelength of light;

[0124] S22: When the temperature of the microring material changes At that time, the change in free spectral range is obtained by using the free spectral range and the initial free spectral range, and the expression is:

[0125] ;

[0126] in, This represents the change in the free spectral range.

[0127] It is important to note that This represents the initial free spectral range.

[0128] S23: Incorporate the initial length and initial refractive index of the microring material, the wavelength of the light wave, the optical path difference, and the proportionality coefficient to simulate the change in the free spectral range and the temperature change of the microring material, eliminating the influence of the temperature change of the microring material on the change in the free spectral range.

[0129] In this embodiment, the silicon nitride operates at a wavelength of 1550 nm. Taking into account the wavelength of the light wave, the initial length of the silicon nitride, the initial refractive index of the silicon nitride, the optical path difference, and the proportionality coefficient of the silicon nitride, the expression is:

[0130] ;

[0131] The change in the free spectral range is simulated, and the change in the free spectral range is as follows: Figure 7 As shown, when the temperature change of silicon nitride is within At this temperature, the change in the free spectral range exhibits a significant nonlinear change, while when the temperature change in silicon nitride is below 100℃, the change in the free spectral range shows a clear linear trend. However, if... Figure 8 As shown, the change in the free spectral range is only about 1.5 pm, which is extremely small and can be ignored because the effect of temperature change of the microring material on the change in the free spectral range is negligible.

[0132] S3: By analyzing the interference pattern of light within the microring, the position of the spectral peak is determined, and the linear relationship between the wavelength shift of the spectral peak and the temperature change of the microring material is determined using the position of the spectral peak.

[0133] S31: The position of the spectral peak is derived by analyzing the interference pattern of light within the micro-ring. The expression is as follows:

[0134] ;

[0135] in, The order of the oscillation spectrum peak. The wavelength of the initial spectral peak;

[0136] S32: When the temperature of the microring material changes At that time, the wavelength shift of the spectral peak is obtained by using the position of the spectral peak and the scaling factor, and the expression is:

[0137] ;

[0138] in, Temperature changes in microring materials The wavelength of the spectral peak, This represents the wavelength shift of the k-th spectral peak.

[0139] It should be noted that, as can be seen from S32, the wavelength shift of the spectral peak and the temperature change of the microring material are linearly related.

[0140] Analysis of the relationship between temperature and voltage of microring material: When the driving voltage is increased, electrical energy is converted into heat energy through the heating resistor, which raises the working temperature of the microring. In this process, the microring absorbs heat from the heating resistor and also dissipates heat through heat transfer with the surrounding environment. Therefore, the microring reaches a certain stable temperature state, which is essentially a dynamic balance process of heat absorption and heat dissipation.

[0141] S4: Establish the fitting relationship between temperature and driving voltage of microring material by using Joule's law and heat transfer laws.

[0142] S41: The heating power of the microring is obtained through Joule's law, expressed as follows:

[0143] ;

[0144] in, The heating power of the microring. The resistance value varies with the temperature of the microring material. For driving voltage, This is the nominal resistance value of the heating resistor. The temperature coefficient of resistance. For reference temperature;

[0145] S42: The heat dissipation power of the micro-ring is obtained through the heat transfer law, and the expression is:

[0146] ;

[0147] in, This refers to the heat dissipation power of the microring. For heat transfer and electrical conductivity, The ambient temperature.

[0148] The thermal conductivity includes thermal conduction from contact with a solid, thermal convection from a fluid medium, and thermal radiation in the form of infrared radiation.

[0149] S43: When the heat dissipation power and heating power of the microring are equal, the temperature of the microring material is determined by the following expression:

[0150] ;

[0151] It should be noted that it is difficult to obtain the relationship between the temperature of the microring material and the driving voltage through the expression in S43, because the temperature of the microring material has little effect on the resistance value that changes with the temperature of the microring material (the temperature change is within 100℃). We can simplify the expression by ignoring the effect of the temperature of the microring material on the resistance value that changes with the temperature of the microring material.

[0152] S44: Excluding the resistance value that varies with the temperature of the microring material, the relationship between the temperature of the microring material and the driving voltage is obtained, expressed as:

[0153] ;

[0154] It should be noted that since the nominal resistance of the heat transfer conductivity and heating resistance is constant, the relationship between the temperature of the microring material and the driving voltage is a quadratic function. Therefore, S45 uses quadratic fitting to obtain the fitting relationship.

[0155] S45: Fit the relationship between the temperature and driving voltage of the microring material to obtain the fitted relationship between the temperature and driving voltage of the microring material, expressed as:

[0156] ;

[0157] in, The coefficient of the quadratic term, The coefficient of the linear term.

[0158] S5: By combining the fitting relationship between the peak wavelength shift and the temperature and driving voltage of the microring material, the peak wavelength expression is obtained. By changing the reference wavelength of the microring, the driving voltage relationship corresponding to different microring peak wavelengths is derived using the peak wavelength expression theory.

[0159] S51: By fitting the wavelength shift of the spectral peak to the temperature and driving voltage of the microring material, the expression for the spectral peak wavelength is obtained:

[0160] ;

[0161] in, The wavelength of the spectral peak. For driving voltage, The ambient temperature is When the microrings are not heated, the temperature of the microring material is the ambient temperature. The reference wavelength of the microring;

[0162] S52: Determine the quadratic and linear coefficients by fixing the order of the spectral peak wavelength, and change the reference wavelength of the microring. The value of is used to predict the driving voltage relationship corresponding to different microring spectral peak wavelengths.

[0163] In this embodiment, in the C-band (the most commonly used band in optical communication, around 1550nm), the order k of the oscillation peak is a relatively large positive integer, approximately 1340~1370. Since the order k of the oscillation peak fluctuates relatively little, a fixed value (e.g., 1340) is selected to simplify the relationship between the peak wavelength and the driving voltage. Based on the fact that a fixed value can approximately unify the variation law of all peaks, that is, the coefficients of the quadratic term and the linear term will be determined. By changing the reference wavelength λ of the constant term microring... k By taking the value of [value], the reference wavelength for different microrings can be predicted. The corresponding peak wavelength-driving voltage relationship.

[0164] It should be noted that, based on theoretical derivation, changing the constant term... By determining the value of λ, the reference wavelength for different microrings can be predicted. k The corresponding peak wavelength-driving voltage relationship was found to be challenging during experiments, particularly in obtaining the variation of peak wavelength with driving voltage and the reference wavelength of the microring. Based on this, research was conducted.

[0165] S6: Correlate the peak wavelength with the driving voltage through quadratic fitting, discard the reference wavelength obtained by fitting, obtain the peak wavelength-driving voltage relationship, obtain the optimal peak wavelength by using the difference between the protocol wavelength and the peak wavelength group, determine the driving voltage by using the optimal peak wavelength to correspond to the reference wavelength and the optimal peak wavelength and the reference wavelength.

[0166] S61: Fix one micro-ring driving voltage, scan another micro-ring driving voltage, collect discrete spectral peaks at coincident resonance, obtain spectral peak wavelengths, and integrate them to obtain a spectral peak wavelength group.

[0167] S62: Perform a second-order fitting between the peak wavelength and the corresponding driving voltage, discard the reference wavelength, and obtain the peak wavelength-driving voltage relationship. ;

[0168] S63: Input the protocol wavelength, calculate the difference between the protocol wavelength and each spectral peak wavelength using the spectral peak wavelength group, and filter out the smallest difference that is greater than zero. Through the minimum difference Determine the optimal spectral peak wavelength and use the optimal spectral peak wavelength to correspond to the reference wavelength;

[0169] S64: Joint peak wavelength-driving voltage relationship and minimum difference The target driving voltage of each of the two microrings is obtained. The target driving voltage is applied to the two microrings through the heater, and the optimal spectral peak wavelength is tuned to the protocol wavelength. The protocol wavelength optical signal is output by utilizing the vernier effect.

[0170] In this embodiment, the variation of the spectral peak wavelength with the driving voltage is obtained using microring one as an example. The driving voltage of microring one is kept constant by fixing the material temperature of microring one. This keeps the spectral peak wavelength of microring one fixed, while controlling the material temperature of microring two to linearly scan the driving voltage of microring two from 0 to... (Different wavelength tuning chips) (There may be differences). The scanning step size is 0.01V. During the change of the driving voltage of microring two, the output spectrum of the laser is collected in real time by a spectrometer. Whenever the resonance peak of microring two coincides with the resonance peak of microring one, the corresponding spectral peak wavelength of the laser starts to oscillate and outputs discrete spectral peaks. Finally, an array of wavelengths corresponding to a series of oscillating spectral peaks is obtained, which is the spectral peak wavelength of microring one (the spectral peak wavelength of microring one when it is not heated and the temperature is equal to the ambient temperature is defined as the reference wavelength of microring one). The method for obtaining the spectral peak wavelength of microring two is the same as that of microring one.

[0171] When extracting the spectral peak wavelength of microring one, the driving voltage of microring one and the driving voltage of microring two corresponding to each spectral peak wavelength are simultaneously recorded and output. A quadratic function is fitted to the spectral peak wavelength and the driving voltage of microring two. The constant term (i.e., the reference wavelength) of the fitted function is discarded, and the quadratic and linear terms of the fitted function are taken to obtain the spectral peak wavelength-driving voltage relationship of microring one. Using the peak wavelength-driving voltage relationship of microring one, the driving voltage relationship corresponding to all peak wavelengths of microring one is predicted. The prediction method for microring two is the same as that for microring one.

[0172] In the prior art, the driving voltage tuning range of a single spectral peak wavelength is limited, and the limit of the change of the spectral peak wavelength with the driving voltage does not exceed twice the FSR (free spectral range). Therefore, it is not possible to directly tune any target wavelength to the ideal position. Only the spectral peak wavelength that is smaller than the target wavelength and closest to the target wavelength can be selected for tuning (this spectral peak wavelength corresponds to a unique reference wavelength).

[0173] In this embodiment, the system receives the protocol wavelength input by the user and distributes it in parallel to the control branches of micro-ring one and micro-ring two. Taking micro-ring one as an example, the system calculates the difference between the protocol wavelength and each spectral peak wavelength of micro-ring one in sequence, stores the difference data in a difference array, and synchronously associates the difference calculation with the corresponding reference wavelength. The system then iterates through the difference array and filters out all differences greater than zero. (Ensure the selected spectral peak wavelength is less than the agreed wavelength), such as Figure 9 As shown, the smallest positive number greater than zero represents the minimum length difference between the protocol wavelength and the wavelength of the peak to be tuned. Each wavelength of the peak to be tuned corresponds to a unique reference wavelength. Similarly, the reference wavelength corresponding to the optimal peak wavelength of microring two can be obtained, based on the peak wavelength-driving voltage relationship of microring one. The minimum difference between the two values ​​that is greater than zero Get expression The target driving voltage of microring one is obtained by solving the problem, and the target driving voltage of microring two can be obtained in the same way. Microring one and microring two adjust their own temperature through their respective heaters according to the calculated target driving voltage, and precisely tune their selected optimal spectral peak wavelength to the protocol wavelength. When both microring resonators meet the resonance condition at the protocol wavelength, according to the vernier effect, the gain at the protocol wavelength will have an absolute advantage in the cavity, thereby suppressing the oscillation of other wavelengths. Finally, the laser will stably output a precise protocol wavelength optical signal.

[0174] Example 2: Verification of wavelength tuning logic and theoretical basis.

[0175] In this embodiment, the driving voltage of the fixed microring is kept constant by controlling the material temperature of the fixed microring. To maintain a fixed reference wavelength for microring one, the driving voltage of microring two is linearly scanned from 0 to 5V with a scan step size of 0.01V, while the material temperature of microring two is controlled. During the change in the driving voltage of microring two, the output spectrum of the laser is acquired in real time using a spectrometer. Whenever the resonant peak of microring two coincides with the resonant peak of microring one, the corresponding spectral peak wavelength of the laser begins to oscillate and outputs discrete spectral peaks. Finally, an array consisting of the wavelengths corresponding to a series of oscillating spectral peaks is obtained, such as... Figure 10 As shown, this is the reference wavelength of microring one. ,like Figure 11 As shown, the reference wavelength of micro-ring one By performing a quadratic function fitting on the driving voltage of microring one and microring two, the relationship between the driving voltage and the spectral peak wavelength of microring one is obtained, and the expression is:

[0176] ;

[0177] A series of reference wavelengths in the figure The fit to the fitted curve is extremely high, and the goodness of fit is excellent. The value reached 0.999959, and the experiment proved the correctness of the theoretical derivation.

[0178] To verify the invention, the reference wavelength of the microring was changed. The accuracy and applicability of predicting the driving voltage relationship corresponding to different microring spectral peak wavelengths across the entire working band are assessed by selecting the shortest reference wavelength within the working band of the microring. With the longest reference wavelength As a typical verification object, the shortest reference wavelength With the longest reference wavelength These correspond to the two boundary wavelengths of the tunable range, and also represent the extreme cases with the largest relative prediction errors.

[0179] like Figure 10 As shown, the shortest reference wavelength The relationship between the driving voltage and the peak wavelength of the microring corresponding to the shortest reference wavelength is obtained, and the expression is:

[0180] ;

[0181] The experimental data points and prediction function curves for the shortest reference wavelength are shown below. Figure 12 As shown, the shortest reference wavelength and the predicted function curve fit together very well, with almost no error visible to the naked eye. In fact, as... Figure 13 As shown, the prediction error of the shortest reference wavelength is very small, less than 12 pm, which meets the engineering requirements.

[0182] like Figure 10 As shown, the longest reference wavelength The relationship between the driving voltage and the peak wavelength of the microring corresponding to the longest reference wavelength is obtained, and the expression is as follows:

[0183] ;

[0184] The experimental data points and predicted function curves for the longest reference wavelength are shown below. Figure 14 As shown, the longest reference wavelength and the prediction function curve fit very well, but the error is greater than the prediction error of the shortest reference wavelength. In fact, as... Figure 15 As shown, the prediction error for the longest reference wavelength is less than 30 pm, which meets engineering requirements.

[0185] The same procedure was applied to microring two, with the material temperature of microring two kept constant and the driving voltage of microring two kept constant. This method keeps the reference wavelength of microring two fixed, while controlling the material temperature of microring one to linearly scan its driving voltage from 0 to 5V with a scan step size of 0.01V. During the change of the driving voltage of microring one, the output spectrum of the laser is acquired in real time using a spectrometer. Whenever the resonant peak of microring one coincides with the resonant peak of microring two, the corresponding spectral peak wavelength of the laser begins to oscillate and outputs discrete spectral peaks. Finally, an array consisting of the wavelengths corresponding to a series of oscillating spectral peaks is obtained, such as... Figure 16 As shown, this is the reference wavelength of microring two. The reference wavelength of microring two By performing a quadratic function fitting on the driving voltage of microring one, the relationship between the driving voltage and the spectral peak wavelength of microring two is obtained, and the expression is:

[0186] ;

[0187] Select the shortest reference wavelength within the working band of the micro-ring two With the longest reference wavelength As a typical verification object, such as Figure 16 As shown, the shortest reference wavelength The relationship between the driving voltage and the peak wavelength of the microring two corresponding to the shortest reference wavelength is obtained, and the expression is:

[0188] ;

[0189] The experimental data points and prediction function curves for the shortest reference wavelength are shown below. Figure 17 As shown, the shortest reference wavelength and the predicted function curve fit very well, with almost no error visible to the naked eye. Figure 18 As shown, the prediction error of the shortest reference wavelength is very small, less than 6 pm, which meets engineering requirements.

[0190] like Figure 16 As shown, the longest reference wavelength The relationship between the driving voltage and the peak wavelength of the second microring corresponding to the longest reference wavelength is obtained, and the expression is:

[0191] ;

[0192] The experimental data points and predicted function curves for the longest reference wavelength are shown below. Figure 19 As shown, the longest reference wavelength and the prediction function curve fit very well, but the error is greater than the prediction error of the shortest reference wavelength. In fact, as... Figure 20 As shown, the prediction error for the longest reference wavelength is less than 20 pm, which meets engineering requirements.

[0193] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A wavelength tuning method based on an external cavity dual-microring laser, characterized in that, Includes the following sub-steps: The optical path difference is obtained by using the thermo-optic coefficient and the thermal expansion coefficient expression. The initial length, thermo-optic coefficient, thermal expansion coefficient and initial refractive index of the microring material are then input to simulate the optical path difference and the temperature change of the microring material, and the proportionality coefficient is obtained. The free spectral range is calculated, and the change in the free spectral range is obtained by using the free spectral range and the initial free spectral range. The change in the free spectral range and the temperature change of the microring material are used for simulation to eliminate the influence of the temperature change of the microring material on the change in the free spectral range. By analyzing the interference pattern of light within the microring, the position of the spectral peak is determined, and the linear relationship between the wavelength shift of the spectral peak and the temperature change of the microring material is determined using the position of the spectral peak. By applying Joule's law and the laws of heat transfer, a fitting relationship between temperature and driving voltage for microring materials was established. By combining the fitting relationship between the peak wavelength shift and the temperature and driving voltage of the microring material, the peak wavelength expression is obtained. Whenever the reference wavelength of the microring is changed, the driving voltage relationship corresponding to different microring peak wavelengths is derived using the peak wavelength expression theory. By correlating the peak wavelength with the driving voltage through a quadratic fitting, the reference wavelength obtained by the fitting is discarded, and the relationship between the peak wavelength and the driving voltage is obtained. The optimal peak wavelength is obtained by using the difference between the protocol wavelength and the peak wavelength group. The driving voltage is determined by the reference wavelength corresponding to the optimal peak wavelength and the reference wavelength.

2. The wavelength tuning method based on an external cavity double-microlaser according to claim 1, characterized in that, The process of obtaining the optical path difference using the thermo-optic coefficient and thermal expansion coefficient expressions, and then simulating the optical path difference and temperature change of the microring material by incorporating the initial length, thermo-optic coefficient, thermal expansion coefficient, and initial refractive index of the microring material to obtain the scaling factor includes the following sub-steps: The expression for the thermo-optic coefficient is obtained by using the temperature and refractive index of the microring material: The expression for the coefficient of thermal expansion is obtained by considering the initial length, length, and temperature of the microring material: When the temperature of the micro-ring material is changed The amount of change in the refractive index and the amount of change in the length of the micro-ring material are obtained through the expressions of the thermal expansion coefficient and the thermo-optic coefficient; When the temperature of the micro-ring material changes The refractive index and length of the micro-ring material are obtained through the change amount of the refractive index and the change amount of the length of the micro-ring material. The initial optical path is obtained by using the initial refractive index and length of the microring material; the optical path difference is obtained by using the initial optical path and the initial optical path. By incorporating the initial length, thermo-optic coefficient, thermal expansion coefficient, and initial refractive index of the microring material, the optical path difference and the temperature change of the microring material are simulated. The proportionality coefficient is obtained through the linear relationship between the optical path difference and the temperature change of the microring material.

3. The wavelength tuning method based on an external cavity dual-microring laser according to claim 2, characterized in that, The optical path difference is expressed as: ； in, The refractive index of the microring material, The length of the microring material, The initial refractive index of the microring material. The initial length of the microring material. This represents the temperature change of the microring material. Thermo-optic coefficient, is the coefficient of thermal expansion.

4. The wavelength tuning method based on an external cavity dual-microring laser according to claim 2, characterized in that, The proportionality coefficient is expressed as follows: ； in, This is the proportionality coefficient. For optical path difference, This represents the temperature change of the microring material.

5. The wavelength tuning method based on an external cavity dual-microring laser according to claim 1, characterized in that, The calculation of the free spectral range, which involves obtaining the change in the free spectral range by comparing the initial free spectral range with the original free spectral range, and then using the change in the free spectral range and the temperature change of the microring material for simulation, eliminates the influence of the temperature change of the microring material on the change in the free spectral range. This includes the following sub-steps: A free spectral range can be obtained by considering the wavelength of light waves, the refractive index of the microring material, and its length. When the temperature of the microring material changes At that time, the change in free spectral range is obtained by comparing the free spectral range with the initial free spectral range; By incorporating the initial length and initial refractive index of the microring material, the wavelength of the light wave, the optical path difference, and the scaling factor, simulations were performed on the changes in the free spectral range and the temperature changes of the microring material, thus eliminating the influence of the temperature changes of the microring material on the changes in the free spectral range.

6. The wavelength tuning method based on an external cavity dual-microring laser according to claim 1, characterized in that, The process of establishing the fitting relationship between temperature and driving voltage of the microring material using Joule's law and heat transfer principles includes the following sub-steps: The heating power of the microrings is obtained through Joule's law; The heat dissipation power of the micro-ring is obtained by understanding the laws of heat transfer; When the heat dissipation power of the microring is equal to the heating power of the microring, the temperature of the microring material is determined. By excluding the resistance value that varies with the temperature of the microring material, the relationship between the temperature of the microring material and the driving voltage is obtained; The relationship between the temperature and driving voltage of the microring material is fitted to obtain the fitting relationship between the temperature and driving voltage of the microring material.

7. The wavelength tuning method based on an external cavity dual-microring laser according to claim 6, characterized in that, The relationship between the temperature and driving voltage of the microring material is expressed as follows: ； in, The temperature of the microring material, For driving voltage, This is the nominal resistance value of the heating resistor. For heat transfer and electrical conductivity, The ambient temperature.

8. The wavelength tuning method based on an external cavity dual-microring laser according to claim 1, characterized in that, The expression for the wavelength of the spectral peak is: ； in, The wavelength of the spectral peak. For driving voltage, This is the proportionality coefficient. The coefficient of the quadratic term, The coefficient of the linear term, The order of the oscillation spectrum peak. The reference wavelength is used.

9. The wavelength tuning method based on an external cavity dual-microring laser according to claim 1, characterized in that, The process of correlating the peak wavelength with the driving voltage through a quadratic fitting, discarding the reference wavelength obtained from the fitting, and obtaining the peak wavelength-driving voltage relationship, using the difference between the protocol wavelength and the peak wavelength group to obtain the optimal peak wavelength, and determining the driving voltage by matching the optimal peak wavelength with the reference wavelength, includes the following sub-steps: By fixing the driving voltage of one micro-ring and scanning the driving voltage of another micro-ring, the discrete spectral peaks at the coincident resonance are collected to obtain the spectral peak wavelengths and integrate them to obtain a spectral peak wavelength group. The peak wavelength is then fitted twice with the corresponding driving voltage, and the reference wavelength is discarded to obtain the peak wavelength. -Drive voltage relation ; Input the protocol wavelength, calculate the difference between the protocol wavelength and the wavelengths of each spectral peak using the spectral peak wavelength group, and filter out the smallest difference that is greater than zero. Through the minimum difference Determine the optimal spectral peak wavelength and use the optimal spectral peak wavelength to correspond to the reference wavelength; Joint peak wavelength-driving voltage relationship and minimum difference The target driving voltage of each of the two microrings is obtained. The target driving voltage is applied to the two microrings through the heater, and the optimal spectral peak wavelength is tuned to the protocol wavelength. The protocol wavelength optical signal is output by utilizing the vernier effect.

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