Laser coupling method and system based on optical wedge

Abstract

The present application discloses a laser coupling method and system based on an optical wedge, which relates to the field of laser coupling technology, including: receiving incident laser, and adjusting the incident angle of the incident laser by adjusting the rotation angle of the optical wedge, wherein the incident angle includes the angle in the horizontal direction and the angle in the vertical direction; detecting the incident power of the incident laser after the incident angle is adjusted; receiving the incident laser after the incident angle is adjusted and coupling to generate a coupled laser; detecting the output power of the coupled laser; using a PID algorithm to generate a drive control signal according to the incident power and the output power; and adjusting the rotation angle of the optical wedge according to the generated drive control signal. In view of the problem of poor stability of the coupled laser power existing in the prior art, the present application improves the stability of the coupled laser output power by adjusting the incident angle of the incident laser on the optical wedge to control the output power of the coupled laser and other technologies.

Description

Technical Field

[0001] The present application relates to the field of laser coupling technology, and in particular to a laser coupling method and system based on an optical wedge. Background Art

[0002] At present, laser technology has been widely used in many fields such as communication, optical measurement, and medical treatment. In order to meet the needs of different applications, it is usually necessary to obtain stable and intensity-controllable lasers. Affected by various factors, it is difficult for a single laser to produce ideal laser output, so laser coupling has become an important means to combine multiple laser outputs.

[0003] In existing laser coupling technology, optical couplers are often used to aggregate the output light of two or more lasers to obtain coupled lasers with greater intensity and adjustable parameters. However, this simple aggregation will introduce new problems, mainly manifested in the unstable intensity of the output coupled laser. The reason is that the parameters of each laser incident on the coupler vary greatly, which will cause fluctuations in the output light intensity after direct coupling. If the output power of the coupled laser is unstable, it will seriously affect the subsequent optical measurement, communication and other processes, reducing their accuracy and effect.

[0004] In the related art, for example, Chinese patent document CN116027500A provides a laser power control method based on a rotating double wedge, including: the double wedge module transmits the incident light beam after power adjustment to the laser coupling module; the laser coupling module couples the adjusted incident light beam and transmits the coupled light beam to the laser beam sampling module; the laser beam sampling module splits the coupled light beam and transmits one of the split light beams to the feedback control module; the feedback control module controls the double wedge module based on the power of the split light beam to adjust the power of the incident light beam until the power of the split light beam is equal to the preset value. However, the present application uses feedback control to adjust the incident laser power, but the feedback signal comes from the sampling of the light beam after laser coupling. The sampling itself will introduce errors and cannot truly reflect the output power changes of the coupled laser, resulting in the need to further improve the power stability of the coupled laser in the present application. Summary of the invention

[0005] 1. Technical issues to be solved

[0006] In response to the problem of poor coupling laser power stability in the prior art, the present application provides a laser coupling method and system based on an optical wedge, which improves the stability of the coupled laser output power by adjusting the incident angle of the incident laser on the optical wedge and other technologies.

[0007] 2. Technical solution

[0008] The purpose of this application is achieved through the following technical solutions.

[0009] One aspect of the embodiments of the present specification provides a laser coupling method based on an optical wedge, comprising: receiving an incident laser, and adjusting the incident angle of the incident laser by adjusting the rotation angle of the optical wedge; detecting the incident power of the incident laser after the incident angle is adjusted; receiving the incident laser after the incident angle is adjusted and coupling to generate a coupled laser; detecting the output power of the coupled laser; using a PID algorithm to generate a drive control signal according to the incident power and the output power; and adjusting the rotation angle of the optical wedge according to the generated drive control signal. A high-precision fiber sampler and an optical filter are used to ensure accurate spectral splitting and filtering of the incident laser. A high-sensitivity detector is used to improve the sensitivity and resolution of incident power detection. The incident laser is received, and the incident angle of the incident laser on the optical wedge is adjusted by adjusting the rotation angle of the optical wedge, thereby regulating the light intensity of the incident laser incident on the coupler. After adjusting the incident angle, the incident power of the adjusted incident laser is detected. This step realizes accurate measurement of the incident power by means of spectral sampling, digital signal processing, etc. The incident laser after adjusting the incident angle is input into the optical coupler for coupling to generate the output laser. The output power of the generated coupled laser is detected. The output power measurement is used as a feedback signal. According to the measured incident power and output power, the driving signal required to control the rotation of the optical wedge is calculated by the PID algorithm. The PID algorithm realizes closed-loop control. According to the control signal calculated by the PID algorithm, the optical wedge is driven to rotate and adjust the incident angle to adjust the output power to achieve stability. The present application realizes accurate control of the output coupled laser power and improves the stability of the output power.

[0010] Specifically, the optical wedge is placed in the incident laser light path, and the angle of the incident laser is adjusted by the refraction effect of the optical wedge. A rotating shaft is provided at one end of the optical wedge, which is connected to a stepper motor, and the stepper motor provides forward and reverse power. By controlling the rotation direction, number of steps and frequency of the stepper motor, the optical wedge is driven to rotate at different angles. After the optical wedge rotates a minimum step angle, the incident point of the incident laser on the optical wedge moves, thereby changing the incident angle.

[0011] Specifically, in the present application, the rotation of the optical wedge is realized by a stepper motor, and the drive of the stepper motor is controlled by the control signal calculated by PID. The initial rotation angle of the optical wedge is set to 0 degrees. According to the incident power and output power fed back, the control signal calculated by the PID algorithm controls the forward and reverse rotation and the number of rotation steps of the stepper motor, thereby driving the optical wedge to rotate to the target angle. The rotation range of the optical wedge is determined to be 0 to 10 degrees. Exceeding this range will result in reduced coupling efficiency. The control signal output by the PID algorithm includes a module for checking the current rotation angle of the optical wedge, and an alarm is given when the rotation angle is about to exceed the range. The minimum step length accuracy of the optical wedge rotation is 0.01 degrees. The stepper motor selects a model with a minimum step angle of 0.01 degrees to meet the accuracy requirements. Set the rotation angle meter of the optical wedge to detect and feedback the current rotation angle of the optical wedge in real time to ensure accurate measurement of the optical wedge angle during PID control. A closed optical path design is adopted to prevent external light from interfering with the precise regulation of the incident laser during the rotation and adjustment of the optical wedge.

[0012] Specifically, the PID algorithm stands for Proportion-Integration-Differentiation algorithm, which is a widely used linear control algorithm. In this application, the steps of generating a drive control signal using the PID algorithm are as follows: calculating the difference e(t) between the incident power and the set target power as the error value; the PID controller calculates the proportional, integral and differential terms of e(t) respectively; weighted superposition of the three values ​​to calculate the final control quantity u(t); using u(t) as the driving control quantity of the stepper motor to drive the optical wedge to rotate to achieve the optimal incident angle. Repeat the above process continuously, adjust the optical wedge angle in real time, and stabilize the coupled laser output.

[0013] Specifically, a laser coupling module is provided to receive incident laser light after the incident angle is adjusted by an optical wedge. A grating coupler is provided in the laser coupling module, and the incident laser light enters the grating coupler for coupling. A pair of diffraction gratings are provided in the grating coupler, and the incident laser light is diffracted by the diffraction gratings and is reflected multiple times between the gratings to achieve coupling amplification. By adjusting the spacing and tilt angle of the gratings, the diffraction direction and coupling efficiency can be controlled. A filter is provided at the output end of the grating coupler to filter out light other than the target wavelength and output the coupled monochromatic laser light.

[0014] A light collecting lens is set at the output end to focus the coupled laser for output. The output end is connected to a power detection module to detect the power of the coupled laser. The detection result is fed back to the PID control system to complete the closed-loop control of the output power. An optional phase correction module can be set to improve coherence and coupling efficiency. The entire laser coupling system works in a controlled environment to ensure stable output power.

[0015] Furthermore, detecting the incident power of the incident laser after adjusting the incident angle also includes the following steps: splitting the incident laser through a fiber optic sampler, and the inlet of the fiber optic sampler and the incident laser are relatively arranged; outputting the split incident laser through the outlet of the fiber optic sampler; filtering the split incident laser output from the fiber optic sampler through an optical filter to remove noise, and the inlet of the optical filter is connected to the outlet of the fiber optic sampler; setting N detection channels, and the inlet of each detection channel is connected to the outlet of the optical filter, where N is a positive integer; performing collaborative filtering on the detection results of the N detection channels through a digital signal processor, and outputting the incident power after the collaborative filtering.

[0016] Among them, the fiber optic sampler is used to split and sample the incident laser, and can be used: Single-mode fiber optic sampler: suitable for applications requiring higher wavelength selectivity and spectral resolution. It can provide higher spectral purity, which helps to accurately detect the power of the incident laser. Multimode fiber optic sampler: suitable for applications that are more sensitive to cost and have a wider wavelength range. However, its spectral resolution is relatively low, which may reduce the accuracy of detection to a certain extent. The splitting efficiency and coupling efficiency of the fiber optic sampler: The splitting efficiency refers to the ability of the fiber optic sampler to separate the incident light into different channels. The coupling efficiency refers to the ability of the fiber optic sampler to collect and output the incident light. The loss in this process should be ensured to be as small as possible to maintain the accuracy and stability of the detection.

[0017] The selection of optical filters is to filter the incident laser light after the splitting output from the fiber sampler to remove noise. In the present application, the optical filter can be used: a narrowband filter has a narrow transmission bandwidth and can selectively transmit light of a specific wavelength, which helps to select the incident laser wavelength of interest in the system and reduce the interference of non-target wavelengths. The tunable filter allows the user to adjust the center wavelength of the filter as needed. This may be beneficial in situations where real-time adaptation to different wavelengths is required. A bandpass filter allows wavelengths within a certain range to pass through while blocking other wavelengths. This helps to further eliminate light of non-target wavelengths. A low-pass filter transmits light below the cutoff frequency and blocks light above the cutoff frequency. This may be effective for eliminating high-frequency noise. A high-pass filter transmits light above the cutoff frequency and blocks light below the cutoff frequency. This helps to filter out low-frequency noise. The bandwidth of the filter should be selected according to the needs of the system and the characteristics of the incident laser. A narrower bandwidth helps to improve spectral resolution, but may result in a decrease in signal strength.

[0018] The detection channel is a channel for receiving, processing and analyzing the optical signal of the incident laser. Each detection channel is responsible for receiving the incident laser signal after splitting output from the fiber sampler. The detection channel contains optical elements, photodiodes, photodetectors, etc., which are used to convert optical signals into electrical signals. Photodiodes or photodetectors are the core components of the detection channel, which are responsible for converting the optical signal of the incident laser into electrical signals. These detectors usually have high sensitivity to ensure effective detection of weak light signals. The detection channel may contain a signal amplifier for amplifying the electrical signal output by the photodiode or photodetector. The function of the amplifier is to enhance the signal strength to improve the sensitivity of the digital signal processor to the optical signal. Each detection channel may be equipped with a filter to further filter out light of non-target wavelengths to reduce noise and improve the signal-to-noise ratio. These filters can be hardware filters or digital filters, depending on the requirements of the system. The output of each detection channel will be connected to a digital signal processor for collecting, processing and analyzing the signals of the detection channel. The digital signal processor may include a collaborative filtering algorithm to collaboratively process the signals of N channels to improve the stability and noise resistance of the system. Set N detection channels, where N is a positive integer. Through multi-channel configuration, the system can detect information from multiple wavelengths or multiple optical channels at the same time, increasing the flexibility and applicability of the system. The output of the detection channel will be used in the real-time feedback control system to adjust the angle of the optical element according to the detected optical power information to maintain a stable incident power.

[0019] Furthermore, N is an even number greater than or equal to 2. Setting multiple redundant detection channels N and performing multi-channel detection is the basis for realizing collaborative filtering to improve detection accuracy and anti-interference ability. Among them, setting N to an even number can make it possible to adopt a packet filtering method in the collaborative filtering algorithm, divide the N detection channels into two subgroups, perform filtering processing in each subgroup, and combine the filtering results of the two subgroups. This packet filtering method can improve the parallelization of filtering operations and enhance real-time performance. N is set to be greater than or equal to 2, which is the most basic number of detection channels for collaborative filtering. Collaborative filtering cannot be achieved with only a single channel. Setting N to an even number can facilitate channel pairwise verification and achieve more reliable error detection and fault tolerance. Setting N to an even number greater than or equal to 2 can achieve at least pairwise channel collaborative filtering. Usually N is set to between 4 and 8, which ensures redundancy and takes cost into consideration.

[0020] Furthermore, the detection results of N detection channels are collaboratively filtered by a digital signal processor, which also includes the following steps: calculating the signal-to-noise ratio SNR(t) of each detection channel at time t, wherein the signal-to-noise ratio SNR(t) is the ratio of the average amplitude of the output signal of each detection channel at time t to the standard deviation; setting the weight coefficient W(t) of each detection channel at time t according to the calculated signal-to-noise ratio SNR(t) at time t; in the collaborative filtering processing at time t, combining the output result output(t-1) obtained by the collaborative filtering processing at the previous time t-1 with the detection result input(t) of each detection channel at the current time t, and using the combination result to correct the detection result input(t) of each detection channel at time t; performing weighted averaging on the corrected detection results input(t) of each detection channel at time t according to the set weight coefficient W(t) at time t, and outputting the incident power output result output(t) after collaborative filtering processing at time t.

[0021] Specifically, for each detection channel, the signal-to-noise ratio SNR(t) at time t is calculated. This is achieved by dividing the average amplitude of the output signal by the standard deviation. Based on the calculated signal-to-noise ratio SNR(t), a corresponding weight coefficient W(t) is set for each detection channel at time t. Generally, channels with higher signal-to-noise ratios should have higher weights in collaborative filtering. In the collaborative filtering processing at time t, the collaborative filtering processing result output(t-1) at the previous time t-1 is combined with the detection result input(t) of each detection channel at the current time t. This can be a simple weighted average or other combination method, depending on the requirements of the system and the algorithm design. Using the combined result, the detection result input(t) of each detection channel at time t is corrected. The purpose of this step is to make more accurate corrections to the detection of each channel through the collaborative processing results. According to the set weight coefficient W(t), the corrected detection results input(t) of each detection channel at time t are weighted averaged. The incident power result output(t) after collaborative filtering processing at time t is output. This is the system's synthesis and correction of the detection results of each channel to obtain more stable and accurate incident power information. Through this collaborative filtering method, the system can more flexibly adjust the weight according to the signal-to-noise ratio of each channel, thereby effectively suppressing noise and improving the stability and accuracy of the system.

[0022] More specifically, input(t) represents the detection result of each detection channel at time t, and each detection channel includes a photodetector and an analog-to-digital converter (ADC). The photodetector detects the incident light signal from the output of the corresponding optical filter and converts it into an analog electrical signal. The ADC samples and digitizes the analog electrical signal and outputs the digitized detection value. The digitized detection value is the detection input input(t) of the detection channel at time t. output(t) represents the collaborative filtering output result at time t, and the detection input input(t) of each detection channel is passed to a digital signal processor (DSP). According to the collaborative filtering algorithm, the DSP uses the output output(t-1) of the previous moment to filter and correct input(t). The input(t) after filtering and correction is weighted averaged, and the collaborative filtering result output(t) at time t is output. In the collaborative filtering algorithm, a weight coefficient W(t) is set for each detection channel, and the signal-to-noise ratio SNR(t) of each detection channel at time t is calculated to reflect the detection accuracy of the detection channel. The SNR(t) of each detection channel is mapped to a value of 0-1 as the weight coefficient W(t) of the channel. The mapping function is selected as follows: when the SNR is within a certain range, W(t) is linearly mapped; when the SNR exceeds this range, W(t) tends to a constant. The weight coefficient W(t) is written into the register of the digital signal processor. The DSP performs a weighted combination of the detection results of each channel according to the W(t) value in the register. For each detection channel, the digital output signal x(t) of the channel at time t is extracted.

[0023] More specifically, calculate the average amplitude A(t) of the signal x(t) in a short period of time near time t. A(t) = (Σ|x(t)|) / N, where N is the number of sampling points. Calculate the standard deviation σ(t) of the signal x(t) in the above short period of time. σ(t) = SQRT(Σ[x(t)-A(t)]^2 / N), calculate the signal-to-noise ratio at time t: SNR(t) = A(t) / σ(t), extract the average amplitude and standard deviation of the signal, and calculate their ratio as the signal-to-noise ratio SNR(t) at that moment, which reflects the accuracy of the signal.

[0024] More specifically, each detection channel includes components such as a photo diode, a preamplifier, and an analog-to-digital converter. At time t, the analog-to-digital converter outputs the digitized signal of the detection channel. Take multiple sampling values ​​of the digital signal within a certain time window, and generally follow a normal distribution after analog-to-digital conversion. Calculate the average amplitude A of the digitized signal sampling values ​​within this time window, which represents the average strength of the signal. Calculate the standard deviation σ of the digitized signal sampling values ​​within this time window, which represents the noise intensity of the signal. The ratio of the average amplitude A to the standard deviation σ is defined as the signal-to-noise ratio SNR(t) of the detection channel at time t. SNR reflects the signal-to-noise intensity of the channel. The larger the SNR, the stronger the signal relative to the noise. By counting the SNR of each channel, the signal quality and detection performance of each channel can be judged. SNR can also be used to determine the weight coefficient of each channel in the collaborative filtering algorithm.

[0025] More specifically, collaborative filtering requires weighted superposition of each detection channel. The weight coefficient reflects the quality of the signal of each channel. Channels with high SNR should have higher weights. According to the SNR(t) calculated for each channel, the weight coefficient W(t) corresponding to the time t can be set. The weight coefficient W(t) and SNR(t) can have a linear positive correlation. The higher the SNR, the larger W. An SNR threshold can also be set. Channels with SNRs higher than the threshold are given higher weights, and those with SNRs lower than the threshold are given lower weights. The weight coefficient also needs to be normalized so that the sum of the weight coefficients of each channel is equal to 1. The weight coefficient W(t) can be multiplied with the signal of each channel in collaborative filtering to achieve weighted superposition of channels. The setting of the weight coefficient needs to comprehensively consider multiple factors such as channel SNR and Enable DISABLE. The weight coefficient can be preset when the system is initialized, or it can be dynamically adjusted during runtime.

[0026] More specifically, in the previous processing, the detection result input(t) of each detection channel at time t was corrected to remove abnormal errors. The weight coefficient W(t) of each channel is calculated, and the larger the weight coefficient, the better the channel quality. The corrected detection result input(t) is multiplied by the weight coefficient W(t) of the corresponding channel. The product results of each channel are summed, that is, the input detection value is weighted superimposed. The superposition sum is divided by the sum of the weight coefficients of each channel and normalized. That is, the weighted average operation of the detection value of each channel is realized. Weighted averaging can reduce the influence of channels with poor quality and give play to the role of channels with better quality. The collaborative filtering result output(t) at the final output time t is the average of the detection values ​​after weight correction. The output result enhances the detection accuracy and anti-interference compared with single channel detection.

[0027] Furthermore, a digital signal processor is used to calculate the difference value diff(t) between the detection result input(t) at the current moment t and the detection result input(t-1) at the previous moment t-1 for each detection channel. The difference value diff(t) calculated by each detection channel is compared with the preset difference threshold th. The difference value reflects the change of the detection result at adjacent moments, and the threshold is used to determine whether the change is significant. When the difference value diff(t) of the detection channel is greater than the preset threshold th, it indicates that the detection result has changed significantly. At this time, the current detection result input(t) of the corresponding detection channel and the previous collaborative filtering output result output(t-1) are used as the input signal of the cascade filter. The cascade filter is applied to the input signal, and the output result output'(t) is obtained after filtering. The cascade filter can use different filtering algorithms, such as a low-pass filter, to smooth the input signal and remove high-frequency noise. The output result output'(t) of the cascade filter is used as the correction result of the corresponding detection channel at moment t. This result will be used for collaborative filtering processing to improve the system's adaptability to changes. By introducing cascade filters, the system can correct the detection results according to the filtering results when the detection channel changes significantly, so as to ensure the timely response of the system to dynamic changes while maintaining smooth filtering of steady-state changes. This strategy helps to better adapt to changes in the actual environment and improve the robustness of the system.

[0028] Specifically, the digital signal processor (DSP) is used to calculate the difference value diff(t) between the detection result input(t) of each detection channel at the current moment t and the detection result input(t-1) at the previous moment t-1. In the present application, the following can be used: a differential operator. The DSP can use the differential operator to perform a simple subtraction operation to calculate the difference between the input at the current moment and the input at the previous moment. The DSP can use a digital differential operation method, such as a differential operation or a differentiator method, to perform a differential operation on the signal to obtain the change between the two moments. The differential equation is a mathematical tool that describes the dynamic behavior of a discrete system. The DSP can calculate the difference between the current moment and the previous moment in the form of a differential equation. The DSP can use a sliding window method to maintain data within a window and calculate the changes between adjacent moments within the window. The FIR filter can be used to calculate the difference between two moments. Digital microprocessor.

[0029] Specifically, for each detection channel, its detection result input(t) is obtained at the current time t, and compared with the detection result input(t-1) of the detection channel at the previous time t-1. The difference in their values ​​is the differential value diff(t), which represents the change in the detection value of the detection channel between two adjacent sampling times. Specifically, the calculation formula of the differential value diff(t) is: diff(t) = input(t) - input(t-1), where input(t) and input(t-1) represent the detection values ​​of the detection channel at the current time t and the previous time t-1, respectively. The differential value diff(t) reflects the change in the detection value of the detection channel between adjacent times.

[0030] Specifically, multiple groups of detection data at time t and t-1 are collected in advance for each detection channel under normal working conditions, and the differential values ​​corresponding to these normal working data are calculated, with the mean value set to μ and the standard deviation set to σ; the differential threshold th is preset to: th = μ + 3σ, and when the differential value diff(t) of the detection channel is greater than the preset threshold th, it is determined that the detection channel is subject to sudden interference at time t. "Sudden interference" refers to the transient change of the detection value of the detection channel in a very short time, whose time duration range is less than the preset time threshold, and the amplitude change exceeds the preset amplitude threshold. Such sudden interference often has a negative impact on the accuracy of the detection result.

[0031] Specifically, when the differential value diff(t) of the detection channel is greater than the preset threshold value th, it is determined that the detection channel is subject to sudden interference at time t, and a cascade filter is used to correct the detection channel, wherein the cascade filter includes two connected first-order low-pass filters, the input end of the first first-order low-pass filter is connected to the current detection result input(t) of the detection channel, and the input end of the second first-order low-pass filter is connected to the previous collaborative filtering output result output(t-1); the outputs of the two first-order low-pass filters are connected to an addition node; the output of the addition node is used as the output result output'(t) of the cascade filter, which is the correction result of the corresponding detection channel at time t. The parameters of the two low-pass filters are respectively configured to different cutoff frequencies, wherein the first low-pass filter is used to suppress high-frequency random noise, and the second low-pass filter is used to retain the effective low-frequency signal.

[0032] Furthermore, the incident angle includes the angle in the horizontal direction and the angle in the vertical direction. Specifically, adjusting the incident angle in two dimensions can achieve more accurate and comprehensive power control. The control accuracy and range of adjusting the angle in only a single direction are limited. The horizontal and vertical angles can form two sets of independent control degrees of freedom, expand the dynamic range of control, and meet a wider range of output power requirements. Considering the angle adjustment in two directions is also more in line with the optical nature, and better coupling and conversion efficiency can be obtained. The two-dimensional adjustment method is more flexible, and the angles in two directions can be adjusted separately or in combination according to specific needs. The use of two-dimensional adjustment is conducive to obtaining lower static errors and better dynamic response characteristics. The two-dimensional adjustment also provides a certain degree of fault tolerance. When the single-direction adjustment fails, the other direction can still be used for adjustment.

[0033] Further, the incident laser after adjusting the incident angle is input into the optical coupler. This can be achieved by an optical element or a device for adjusting the incident angle to ensure that the laser enters the optical coupler in an appropriate manner. A grating structure is set inside the optical coupler, which is used to modulate the phase of the incident laser. The grating structure can be a grating with a specific period, which is used to introduce an optical path difference, thereby affecting the phase of the laser. The phase of the incident laser is modulated by the grating structure. This can be achieved by changing the refractive index, period or direction of the grating. The purpose of phase modulation is to introduce a certain optical path difference so that the coupled laser has a specific phase characteristic. The output power of the coupled laser is detected. This can be achieved by using an optical power detector at the output end of the optical coupler. The change in output power reflects the modulation effect of the grating structure on the phase of the incident laser. When the detected output power is lower than a preset threshold, feedback control is started. This may indicate that the modulation effect of the grating structure is not sufficient to generate sufficient output power. The grating structure is controlled to change the phase of the incident laser. This can be achieved by adjusting the parameters of the grating, such as the refractive index, period or direction. The purpose is to make the phase of the laser incident on the optical coupler randomly distributed. Output power detection and phase adjustment are repeated until the detected output power reaches or exceeds the preset threshold. This ensures that the output power of the generated coupled laser remains at a stable level and the phase meets the requirements. Through this feedback control mechanism, the system can achieve real-time adjustment of the generated coupled laser output to maintain stable output power.

[0034] Furthermore, two grating structures are arranged inside the optical coupler. Each grating includes a set of driving devices. The function of these gratings is to modulate the phase of the incident laser in the horizontal and vertical directions. Each grating structure includes a set of driving devices for controlling the movement of the grating in the horizontal or vertical direction. The driving device of one grating drives the grating to move in the horizontal direction, while the driving device of the other grating drives the grating to move in the vertical direction. The driving directions of the two gratings are perpendicular to each other. The output power is detected to monitor the output power of the coupled laser. When it is detected that the output power is lower than a preset threshold, the corresponding adjustment measures are triggered. When it is detected that the output power is lower than the threshold, the driving device is started. According to the preset time and step size, the two gratings are driven to move alternately in the horizontal and vertical directions. This alternating movement causes the diffraction direction of the incident laser by the two gratings to change. By changing the diffraction direction of the incident laser by the two gratings, the difference between the initial phase of the incident laser incident to the laser coupler and the phase after diffraction changes continuously. Such a change causes the phase to be randomly distributed, so that the output coupled laser shows randomness in phase. By regularly and alternately adjusting the diffraction directions of the two gratings, the phase difference of the laser incident on the laser coupler is ensured to change continuously and eventually present a random distribution characteristic. By dynamically adjusting the grating structure, the phase of the incident laser is changed, thereby achieving a random distribution of the output laser phase.

[0035] Specifically, optical couplers play a key role in generating coupled lasers. An optical coupler is an optical device used to transmit an incident light beam from one optical waveguide (or optical fiber) to another, allowing optical signals to be coupled, separated, multiplexed or modulated in an optical system. In the present application, optical couplers can be used: Fiber couplers can be used to transmit light beams from one optical fiber to another. They can effectively couple light energy from one optical fiber to another. Waveguide couplers are used to transmit light beams between optical waveguides. They can be planar waveguides, photonic crystal waveguides, or other types of waveguide structures. Grating couplers use grating structures to transmit light beams from one waveguide to another. The transmission and coupling characteristics of the incident light can be controlled and adjusted through the specific structure and parameters of the grating. A microring coupler is a device that realizes optical transmission and coupling through the geometric structure of a microring. The special structure of the microring enables the transmission and coupling of light. A polarization coupler couples light of different polarizations. This coupler can transmit light energy from one waveguide to another according to the polarization state of the incident light. Optomechanical couplers use micromechanical systems (MEMS) or other mechanical structures to adjust the transmission direction and coupling efficiency of light beams.

[0036] Specifically, when the output power is detected to be lower than the threshold, the grating structure is controlled to change the phase of the incident laser so that the phase of the incident laser incident on the optical coupler is randomly distributed, that is, the phase change of the incident laser has no fixed pattern and presents a random disordered change. "Random distribution" means that the phase of the incident laser changes in a random and non-fixed pattern within a phase range. The phase value is not concentrated at a certain point, but is evenly dispersed in the entire phase range.

[0037] Specifically, when the output power is detected to be lower than the threshold, the driving device drives the two gratings to move alternately in the horizontal direction and the vertical direction according to the preset time interval Δt and the preset step length Δd, drives the first grating to move in the horizontal direction according to the step length Δd, and the driving time interval is Δt; drives the second grating to move in the vertical direction according to the step length Δd, and the driving time interval is Δt; repeats, and alternately changes the positions of the two gratings; wherein the preferred time interval Δt in the present application is set to 0.1 seconds; the step length Δd is set to the grating displacement corresponding to the movement of the grating diffraction spot for half a cycle. By the above-mentioned method of alternately driving the two gratings, the diffraction direction of the incident laser by the two gratings is changed, so that the phase of the incident laser incident on the coupler is randomly distributed.

[0038] Furthermore, the driving device is a piezoelectric ceramic driving device. Piezoelectric ceramics have the advantage of fast response speed and can realize high-speed and precise driving of the grating. Piezoelectric ceramics can provide a large driving force to meet the needs of moving and adjusting the grating. Piezoelectric ceramics have no magnetic field interference and are suitable for integration with precision optical devices to avoid interference with the grating. Piezoelectric ceramics can realize precise micro-displacement control, which is conducive to fine-tuning the grating diffraction angle.

[0039] Another aspect of the embodiments of the present specification also provides a system based on the optical wedge-based laser coupling method of the present application, including: a first optical wedge module, used to receive an incident laser, and adjust the incident angle of the incident laser in the horizontal direction by adjusting the rotation angle; a second optical wedge module, used to receive the incident laser, and adjust the incident angle of the incident laser in the vertical direction by adjusting the rotation angle; a first power detection module, used to detect the incident power of the incident laser after the incident angle is adjusted by the first optical wedge module and the second optical wedge module; a laser coupling module, receiving the incident laser adjusted by the first optical wedge module and the second optical wedge module for coupling to generate a coupled laser; a second power detection module, used to detect the output power of the coupled laser; a control module, used to generate a drive control signal according to the incident power and the output power using a PID algorithm; a drive module, receiving the drive control signal, and adjusting the rotation angles of the first optical wedge module and the second optical wedge module respectively according to the received drive control signal.

[0040] The first optical wedge module and the second optical wedge module respectively adjust the incident angle of the incident laser in the horizontal and vertical directions by adjusting the rotation angle. The first power detection module detects the incident power of the incident laser after the incident angle is adjusted. The second power detection module detects the output power of the coupled laser. The adjusted incident laser is coupled through the laser coupling module to generate a coupled laser. The control module adopts a PID algorithm to generate a driving control signal according to the incident power and the output power. The driving module adjusts the rotation angles of the first optical wedge module and the second optical wedge module according to the driving control signal.

[0041] 3. Beneficial effects

[0042] Compared with the prior art, the advantages of this application are:

[0043] (1) By using an optical wedge to adjust the incident laser angle and closed-loop PID control, the output power of the coupled laser can be adjusted and stabilized in real time, thereby improving the stability of the output power;

[0044] (2) Accurately test the incident laser power by using spectroscopic sampling, digital signal processing and multi-channel detection, providing accurate feedback input for subsequent PID closed-loop control and improving control accuracy;

[0045] (3) The grating structure is set to modulate the phase of the incident laser in real time. This mechanism is enabled when the output power is detected to be too low. This can quickly optimize the output power of the coupled laser and prevent the output power from being continuously lower than the threshold. This improves the adaptive ability of the system and thus improves the stability of the coupled laser output power. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] This specification will be further described in the form of exemplary embodiments, which will be described in detail by the accompanying drawings. These embodiments are not restrictive, and in these embodiments, the same number represents the same structure, wherein:

[0047] Figure 1 is an exemplary flow chart of a laser coupling method based on an optical wedge according to some embodiments of this specification;

[0048] Figure 2 is an exemplary flow chart of detecting incident power according to some embodiments of this specification;

[0049] Figure 3 is an exemplary flow chart of generating coupled laser according to some embodiments of this specification;

[0050] Figure 4 is an exemplary module diagram of a wedge-based laser coupling system according to some embodiments of the present specification. DETAILED DESCRIPTION

[0051] The method and system provided in the embodiments of this specification are described in detail below with reference to the accompanying drawings.

[0052] Figure 1 is an exemplary flow chart of a laser coupling method based on an optical wedge according to some embodiments of this specification, such as Figure 1 As shown, a laser coupling method based on an optical wedge includes: S110 receiving an incident laser, and adjusting the incident angle of the incident laser by adjusting the rotation angle of the optical wedge; the incident angle includes the angle in the horizontal direction and the angle in the vertical direction. S120 detecting the incident power of the incident laser after the incident angle is adjusted; S130 receiving the incident laser after the incident angle is adjusted and coupling to generate a coupled laser; S140 detecting the output power of the coupled laser; S150 using a PID algorithm to generate a drive control signal according to the incident power and the output power; S160 adjusting the rotation angle of the optical wedge according to the generated drive control signal.

[0053] Specifically, an incident laser is received. The incident laser can be provided by a laser, and the laser has a certain divergence angle. The rotation angle of the optical wedge is adjusted to adjust the incident angle of the incident laser. The optical wedge is a dual-axis structure, which can change the incident angle of the incident laser in the horizontal direction and the vertical direction respectively. The incident power of the adjusted incident laser is detected. The power of the incident light is detected and filtered by using multi-channel redundant detection and digital signal processing technology, and an accurate incident power value is output. The adjusted incident laser is received and coupled by using an optical coupler to generate a coupled light output. The output power of the coupled light is detected. A PID (proportional-integral-differential) algorithm is used to generate a driving control signal of the optical wedge according to the detected incident power and output power. According to the control signal generated by the PID algorithm, the rotation of the optical wedge is driven to adjust the incident angle in real time to maximize the output coupled light power. Through the above method, the system can automatically optimize the incident angle of the input light, optimize the laser coupling efficiency, thereby improving the stability of the system and the light utilization efficiency.

[0054] In a specific embodiment of the present application, a single-mode laser outputs a laser with a certain divergence angle and enters a temperature tuning module. Two precise thermally controlled wedges are arranged in the module, which can fine-tune the angles of the incident light in the horizontal and vertical directions. The incident light power is detected using a fiber sampler and a detection circuit. The incident light is coupled to the output optical fiber through a grating, and the power of the coupled light is detected. The PID controller receives the above detection results, generates a control signal, and accurately drives the constant temperature module of the optical wedge. Through closed-loop control, the incident angle is adjusted in real time so that the output power is stabilized at the maximum value point. Ultimately, the control accuracy of the output wavelength of the fiber laser reaches ±0.01nm.

[0055] In summary, through this closed-loop control method, the angle of the optical wedge is continuously optimized to improve the stability of the coupled laser power. Accurate control of the incident angle is the key to obtaining stable output, and the PID algorithm can adjust the control amount according to the real-time feedback of the optical power, thereby effectively suppressing the influence of various unstable factors on the system. The coordinated cooperation of each step can give full play to the advantages of the optical wedge to control the incident angle and the PID closed-loop control, and enhance the stability of laser coupling.

[0056] Figure 2 is an exemplary flow chart of detecting incident power according to some embodiments of this specification, such as Figure 2 As shown, the incident power of the incident laser after adjusting the incident angle is detected, and the following steps are also included: S121 splits the incident laser through the optical fiber sampler, and the inlet of the optical fiber sampler and the incident laser are arranged relatively; S122 outputs the split incident laser through the outlet of the optical fiber sampler; S123 filters the split incident laser output from the optical fiber sampler through an optical filter to remove noise, and the inlet of the optical filter is connected to the outlet of the optical fiber sampler; S124 sets N detection channels, and the inlet of each detection channel is connected to the outlet of the optical filter, N is a positive integer; N is an even number greater than or equal to 2. S125 performs collaborative filtering on the detection results of the N detection channels through a digital signal processor, and outputs the incident power after collaborative filtering.

[0057] Among them, an optical fiber sampler is used to sample and split the incident laser. The inlet of the sampler is set corresponding to the propagation path of the incident laser for sampling. The outlet of the sampler outputs the split incident laser. The sampled incident laser is transmitted to the optical filter for filtering to remove noise interference. N detection channels are set for parallel detection, and N is an even number greater than or equal to 2, such as 4 detection channels. The inlet of each detection channel is connected to the outlet of the filter. The detection results of the N detection channels are input into the digital signal processor for collaborative filtering algorithm processing. In collaborative filtering, the weight is adjusted in real time according to the signal-to-noise ratio of each channel; and recursive filtering is used to correct burst interference. After digital signal processing, an accurate incident laser power result is output. In this way, through multi-path detection redundancy, digital filtering processing and adaptive algorithm, the detection accuracy and reliability of the incident laser power can be effectively improved to meet the requirements of the optical coupling system for incident power detection.

[0058] The signal-to-noise ratio SNR(t) of each detection channel at time t is calculated, wherein the signal-to-noise ratio SNR(t) is the ratio of the average amplitude of the output signal of each detection channel at time t to the standard deviation; according to the calculated signal-to-noise ratio SNR(t) at time t, the weight coefficient W(t) of each detection channel at time t is set; in the collaborative filtering processing at time t, the output result output(t-1) obtained by the collaborative filtering processing at the previous time t-1 is combined with the detection result input(t) of each detection channel at the current time t, and the detection result input(t) of each detection channel at time t is corrected using the combined result; the corrected detection result input(t) of each detection channel at time t is weighted averaged according to the set weight coefficient W(t) at time t, and the incident power output result output(t) after collaborative filtering processing at time t is output.

[0059] Specifically, a digital signal processor is used to calculate, for each detection channel, the difference value diff(t) between the detection result input(t) of the corresponding detection channel at the current moment t and the detection result input(t-1) at the previous moment t-1; the difference value diff(t) calculated for each detection channel is compared with a preset difference threshold th; when the difference value diff(t) of the detection channel is greater than the preset threshold th, the current detection result input(t) of the corresponding detection channel and the previous collaborative filtering output result output(t-1) are used as input signals of the cascade filter, and the output result output'(t) after cascade filtering is used as the correction result of the corresponding detection channel at moment t.

[0060] In a specific embodiment of the present application, in the embodiment of the above-mentioned fiber laser temperature tuning module, the specific implementation scheme for detecting the incident power is: using a 2x1 fiber coupler, 10% of the incident light is extracted for detection. The sampling light passes through a bandpass optical filter to remove noise. Four PIN-type photodetectors are set in parallel to detect the sampling light and convert it into a current signal. After I / V conversion and amplification, the four current signals enter the FPGA chip for ADC sampling. The FPGA implements an adaptive filtering algorithm, including: calculating the signal-to-noise ratio of each channel and adjusting the weight; performing a recursive filter to eliminate sudden interference. After digital signal processing, an accurate and stable incident light power value is output. When the incident power is too high, the adjustable attenuator in front of the fiber coupler is controlled to adjust the incident.

[0061] In summary, fiber sampling can obtain accurate samples of incident laser light. Optical filtering improves the signal-to-noise ratio of the sample. Multiple detection channels perform redundant detection to improve detection accuracy. Collaborative filtering further reduces noise and improves detection accuracy. The coordinated use of sampling, filtering, multi-channel detection, and collaborative filtering greatly improves the accuracy and anti-interference ability of incident power detection.

[0062] Figure 3 is an exemplary flow chart of generating coupled laser according to some embodiments of this specification, such as Figure 3 As shown, generating a coupled laser also includes the following steps: S131 inputting the incident laser after adjusting the incident angle into the optical coupler to generate a coupled laser; S132 setting a grating structure inside the optical coupler and using the grating structure to modulate the phase of the incident laser; S133 detecting the output power of the coupled laser; S134 when the detected output power is lower than the threshold, controlling the grating structure to change the phase of the incident laser so that the phase of the incident laser incident to the optical coupler is randomly distributed.

[0063] The grating structure includes two gratings, each grating includes a set of driving devices, and the driving devices drive the corresponding grating to move in the horizontal direction or the vertical direction; the driving device of one grating drives the grating to move in the horizontal direction, and the driving device of the other grating drives the grating to move in the vertical direction, and the driving directions of the two gratings are perpendicular to each other; when the output power is detected to be lower than the threshold, the driving device drives the two gratings to move alternately in the horizontal direction and the vertical direction according to the preset time and step length to change the diffraction direction of the incident laser by the two gratings, so that the difference between the initial phase of the incident laser incident to the laser coupler and the phase after diffraction changes continuously and is randomly distributed. Specifically, the driving device is a piezoelectric ceramic driving device.

[0064] In a specific embodiment of the present application, in the above-mentioned fiber laser temperature tuning system, a specific implementation scheme for generating coupled laser is as follows: the laser after the incident angle is adjusted by the optical wedge enters the grating coupler. Two vertical comb gratings are arranged inside the coupler, and each grating is equipped with a piezoelectric ceramic driver. The output power of the coupled laser is detected and fed back to the FPGA. When the output power decreases, the FPGA controls the two gratings to move alternately and change the diffraction direction. The movement of the two gratings ultimately makes the phase of the incident light randomly distributed, thereby improving the coupling efficiency. The grating is driven according to a preset curve, and the alternating movement time and step size are optimized. The output optical fiber transmits the stable single-mode laser obtained by grating coupling. In this way, in the system, the input light with maximum power is first obtained by optical wedge adjustment, and then the output power is further stabilized by grating modulation. The present application combines the grating modulation phase with the adaptive adjustment of the optical wedge to effectively improve the output performance of the fiber laser.

[0065] In summary, the phase of the incident laser is modulated using a grating structure, which provides a means for subsequent random phase modulation. The output power is detected and compared with the threshold to determine the need for phase modulation. When the output power is lower than the threshold, two mutually perpendicular gratings are driven to move alternately in the horizontal and vertical directions, so that the phase of the incident light is randomly distributed. A piezoelectric ceramic drive device is used to drive the grating movement to provide precise phase modulation control. Randomly changing phase can effectively suppress output power fluctuations caused by laser interference, etc. Detection feedback and phase random modulation form a closed-loop control to continuously stabilize the output power. In summary, the combination of phase random modulation and closed-loop control makes full use of the technical means of grating modulation phase, effectively suppresses output power fluctuations caused by various factors, and thus significantly improves the stability and reliability of laser coupling.

[0066] Figure 4 is an exemplary module diagram of a laser coupling system based on an optical wedge according to some embodiments of this specification, such as Figure 4 As shown, the present application provides a laser coupling system 200 based on an optical wedge, which is used to perform a laser coupling method based on an optical wedge of the present application, wherein a first optical wedge module 210 is used to receive an incident laser and adjust the incident angle of the incident laser in the horizontal direction by adjusting the rotation angle; a second optical wedge module 220 is used to receive an incident laser and adjust the incident angle of the incident laser in the vertical direction by adjusting the rotation angle; a first power detection module 230 is used to detect the incident power of the incident laser after the incident angle is adjusted by the first optical wedge module and the second optical wedge module; a laser coupling module 240 receives the incident laser adjusted by the first optical wedge module and the second optical wedge module for coupling to generate a coupled laser; a second power detection module 250 is used to detect the output power of the coupled laser; a control module 260 is used to generate a driving control signal according to the incident power and the output power by using a PID algorithm; a driving module 270 receives the driving control signal and adjusts the rotation angles of the first optical wedge module and the second optical wedge module respectively according to the received driving control signal.

[0067] Specifically, two precision thermally controlled wedge modules can adjust the angles of the incident laser in the horizontal and vertical directions respectively. Redundant detection and digital signal processing are used to improve the accuracy of incident power detection. The grating coupler module, with a built-in grating structure, can modulate the phase of the incident light in real time. The PID control module generates control signals based on the incident and output power. The drive module accurately controls the motion state of the two wedges. The wedge module adaptively adjusts the incident angle to maximize the incident power; the grating module can further improve the stability of the output power; the combination of the two can greatly improve the system output power. The precise control of the wedge and the grating phase modulation technology are integrated to give full play to the synergistic effect of the two in improving the stability of laser coupling power.

[0068] The invention of the present application and its implementation methods are described schematically above. The description is not restrictive. Without departing from the spirit or basic features of the present application, the present application can be implemented in other specific forms. What is shown in the accompanying drawings is only one of the implementation methods of the invention of the present application. The actual structure is not limited to this. Any figure mark in the claims should not limit the claims involved. Therefore, if a person of ordinary skill in the art is inspired by it, without departing from the purpose of the present invention, a structural method and an embodiment similar to the technical solution are designed without creativity, which should all fall within the scope of protection of this patent. In addition, the word "including" does not exclude other elements or steps, and the word "one" before the element does not exclude the inclusion of "multiple" elements. The multiple elements stated in the product claim can also be implemented by one element through software or hardware. The words first, second, etc. are used to indicate names, and do not indicate any specific order.

Claims

1. A laser coupling method based on an optical wedge, comprising: receiving incident laser light and adjusting the incident angle of the incident laser light by adjusting the rotation angle of the optical wedge; Detecting the incident power of the incident laser after adjusting the incident angle; receiving incident laser light after adjusting the incident angle and performing coupling to generate coupled laser light; Detect the output power of the coupled laser; Using PID algorithm, the drive control signal is generated according to the incident power and target power; adjusting the rotation angle of the optical wedge according to the generated drive control signal; Detecting the incident power of the incident laser after adjusting the incident angle also includes the following steps: The incident laser is split by a fiber optic sampler, and the entrance of the fiber optic sampler and the incident laser are arranged relative to each other; The incident laser beam after splitting is outputted through the outlet of the optical fiber sampler; The incident laser beam after the splitting outputted from the optical fiber sampler is filtered by an optical filter to remove noise, and the inlet of the optical filter is connected to the outlet of the optical fiber sampler; N detection channels are set, and the inlet of each detection channel is connected to the outlet of the optical filter, and N is a positive integer; The detection results of the N detection channels are processed by collaborative filtering through a digital signal processor, and the incident power after the collaborative filtering processing is output; The detection results of the N detection channels are collaboratively filtered by a digital signal processor, and the following steps are also included: Calculate the signal-to-noise ratio SNR(t) of each detection channel at time t, where the signal-to-noise ratio SNR(t) is the ratio of the average amplitude of the output signal of each detection channel at time t to the standard deviation; According to the calculated signal-to-noise ratio SNR(t) at time t, the weight coefficient W(t) of each detection channel at time t is set; In the collaborative filtering process at time t, the output result output(t-1) obtained by the collaborative filtering process at the previous time t-1 is combined with the detection result input(t) of each detection channel at the current time t, and the detection result input(t) of each detection channel at time t is corrected using the combined result; The detection results input(t) of each detection channel at time t after correction are weighted averaged according to the weight coefficient W(t) set at time t, and the incident power output result output(t) after collaborative filtering processing at time t is output.

2. The laser coupling method based on optical wedge according to claim 1, characterized in that: In the collaborative filtering process at time t, the detection result input (t) of each detection channel at time t is corrected using the combination result, and the following steps are also included: Using a digital signal processor, for each detection channel, calculate the difference value diff(t) between the detection result input(t) of the corresponding detection channel at the current time t and the detection result input(t-1) at the previous time t-1; The differential value diff(t) calculated by each detection channel is compared with the preset differential threshold th; When the differential value diff(t) of the detection channel is greater than the preset threshold th, the current detection result input(t) of the corresponding detection channel and the previous collaborative filtering output result output(t-1) are used as the input signals of the cascade filter, and the output result output'(t) after cascade filtering is used as the correction result of the corresponding detection channel at time t.

3. The laser coupling method based on optical wedge according to claim 1, characterized in that: N is an even number greater than or equal to 2.

4. The laser coupling method based on optical wedge according to claim 1, characterized in that: The incident angle includes the horizontal angle and the vertical angle.

5. The laser coupling method based on optical wedge according to claim 4, characterized in that: Generating coupled laser also includes the following steps: The incident laser after adjusting the incident angle is input into the optical coupler to generate coupled laser; A grating structure is arranged inside the optical coupler, and the phase of the incident laser is modulated by the grating structure; Detect the output power of the coupled laser; When the detected output power is lower than a threshold, the grating structure is controlled to change the phase of the incident laser so that the phase of the incident laser incident on the optical coupler is randomly distributed.

6. The laser coupling method based on optical wedge according to claim 5, characterized in that: The phase of the incident laser beam incident on the optical coupler is randomly distributed, and the steps further include: The grating structure includes two gratings, each grating includes a set of driving devices, and the driving device drives the corresponding grating to move in the horizontal direction or the vertical direction; A driving device of one grating drives the grating to move in a horizontal direction, and a driving device of another grating drives the grating to move in a vertical direction, and the driving directions of the two gratings are perpendicular to each other; When it is detected that the output power is lower than the threshold, the driving device drives the two gratings to move alternately in the horizontal and vertical directions according to the preset time and step size to change the diffraction direction of the incident laser by the two gratings, so that the difference between the initial phase of the incident laser incident to the laser coupler and the phase after diffraction changes continuously and presents a random distribution.

7. The laser coupling method based on optical wedge according to claim 6, characterized in that: The driving device is a piezoelectric ceramic driving device.

8. A system based on the laser coupling method based on an optical wedge according to any one of claims 1 to 7, comprising: A first optical wedge module is used to receive incident laser light and adjust the incident angle of the incident laser light in the horizontal direction by adjusting the rotation angle; A second optical wedge module is used to receive incident laser light and adjust the incident angle of the incident laser light in a vertical direction by adjusting the rotation angle; A first power detection module, used to detect the incident power of the incident laser after the incident angle is adjusted by the first optical wedge module and the second optical wedge module; A laser coupling module receives the incident laser adjusted by the first optical wedge module and the second optical wedge module for coupling to generate a coupled laser; A second power detection module, used to detect the output power of the coupled laser; A control module, for generating a driving control signal according to incident power and output power by using a PID algorithm; The driving module receives the driving control signal and adjusts the rotation angles of the first optical wedge module and the second optical wedge module respectively according to the received driving control signal.

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