Linear frequency modulated continuous wave laser, calibration method and algorithm processing flow during calibration

Abstract

The present invention discloses a linear frequency modulated continuous wave laser with an on-chip integrated calibration device, comprising a gain chip and a silicon photonic external cavity chip. The calibration device is integrated on the silicon photonic external cavity chip. An edge coupler, a first direct coupler, a phase control region, a beam splitter, a microring filter, and a second direct coupler are sequentially arranged on the silicon photonic external cavity chip. The edge coupler, the first direct coupler, the phase control region, the beam splitter, the microring filter, and the second direct coupler are all waveguide structures on the silicon photonic external cavity chip and are all connected by silicon waveguides. The present invention also discloses a linear frequency modulated continuous wave laser calibration method and an algorithm processing flow during the linear frequency modulated continuous wave laser calibration process. Advantages: The present invention integrates the calibration device on the silicon photonic external cavity chip, eliminating the need for external placement, thereby improving the device's integration and reducing costs.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor laser frequency modulation interference sensing and measurement technology, and in particular to a linear frequency modulation continuous wave laser, a calibration method and an algorithm processing flow during the calibration process. Background Art

[0002] The FM signal transmitter is an essential component for LFM radar transmission. The electrical signal generator generates an electrical signal to modulate the LFM signal. The FM linearity of the FM signal transmitter determines the signal quality of the LFM radar, as well as its ranging accuracy and range. The greater the FM linearity, the lower the signal quality, ranging accuracy, and range. FM linearity is driven by FM nonlinearity, which is primarily caused by the nonlinear response between the drive circuit's electrical signal and the FM signal. Accurately evaluating and calculating the response parameters of this FM nonlinearity is key to implementing FM radar.

[0003] In frequency-modulated continuous-wave interferometry systems, signal nonlinearity is eliminated by directly correcting the output frequency. There are two main methods: open-loop correction and closed-loop correction. The open-loop correction method essentially seeks a specific form of nonlinearly modulated driving signal that causes the semiconductor laser's output frequency to vary linearly over time. By measuring the output frequency under different input conditions, a database is established, and the driving signal waveform that linearizes the laser's output frequency is fitted. The closed-loop correction method uses a delayed self-heterodyne optoelectronic phase-locked loop to establish a feedback loop. This involves using the interferometer optical path to convert the laser's frequency modulation slope into the interferometer beat signal frequency. The frequency or phase is then used as a closed-loop correction variable, and negative feedback is used to compensate for the beat signal's frequency difference. By stabilizing the interferometer beat signal frequency, the modulation slope of the laser output signal is stabilized, effectively linearizing the laser's output frequency modulation signal. The open-loop correction method offers a simple hardware system structure and is easy to implement, but suffers from low linear frequency modulation accuracy. Closed-loop correction methods can achieve high-precision nonlinearity correction, but the system is complex and, due to the limited locking range of the optoelectronic phase-locked loop, the linear frequency modulation range is greatly restricted. Both open-loop and closed-loop correction methods are pre-correction methods and require the use of an additional correction optical path. This involves pre-adjusting the semiconductor laser drive current to linearize the semiconductor laser output frequency modulation, thereby correcting the nonlinearity of the frequency-modulated interference signal. Summary of the Invention

[0004] The purpose of the present invention is to propose a linear frequency modulated continuous wave laser with an on-chip integrated calibration device to solve the nonlinear problem of linear frequency modulated continuous wave lasers in low-cost applications. It can achieve monolithic integration, does not require an external calibration optical path, has a simple structure and is easy to operate.

[0005] The technical solutions adopted are:

[0006] A linear frequency modulated continuous wave laser with an on-chip integrated calibration device comprises a gain chip and a silicon photonic external cavity chip. The calibration device is integrated on the silicon photonic external cavity chip and is used to evaluate and calculate the response parameters of the frequency modulation nonlinear term to achieve linear output. An edge coupler, a first direct coupler, a phase-controlled region, a beam splitter, a microring filter, and a second direct coupler are sequentially arranged on the silicon photonic external cavity chip. The edge coupler, the first direct coupler, the phase-controlled region, the beam splitter, the microring filter, and the second direct coupler are all waveguide structures on the silicon photonic external cavity chip and are all connected by a silicon waveguide.

[0007] The gain chip and the silicon photonic external cavity chip form a laser through end-face coupling, and the edge coupler is connected to the gain chip through end-face coupling. The light is transmitted through the silicon waveguide to the first direct coupler and is divided into two paths. One signal light first enters the phase-controlled region along the silicon waveguide, and then is split into two by the beam splitter and enters the microring filter before being recombined and returned to the original path; the other signal light propagates along another silicon waveguide to the second direct coupler and is then divided into two light paths. Most of the signal light is output from the out end as the output signal, and a small part of the signal is transmitted to the calibration device via the silicon waveguide.

[0008] In a further preferred embodiment of the technical solution of the present invention, both ends of the gain chip are coated with a high-reflection film and an anti-reflection film, respectively, and the edge coupler should match the gain chip mode spot to reduce the end face coupling loss.

[0009] In a further preferred embodiment of the technical solution of the present invention, the phase-controlled region is composed of a silicon waveguide and a heating electrode above it, and the refractive index of the waveguide is changed by electrothermal heating of the electrode, thereby changing the phase of the signal light, and precise control of the wavelength is achieved through phase tuning, that is, it is used to achieve frequency scanning.

[0010] In a further preferred embodiment of the present invention, the microring filter comprises multiple microrings and heating electrodes positioned above them, achieving filtering based on the Vernier effect. By applying power to the electrodes, the effective refractive index of the microring waveguide is altered, thereby changing the resonant wavelength of the microring and controlling the center wavelength.

[0011] In a further preferred embodiment of the present invention, the first direct coupler has a 1x2 structure, enabling light to be emitted from the laser external cavity chip. The second direct coupler has a splitting ratio of 9:1, with most of the light being output as the output signal from the output port, and a small portion of the light being transmitted as the calibration signal via the silicon waveguide to the calibration device.

[0012] In a further embodiment of the technical solution of the present invention, the calibration device includes a Mach-Zehnder interferometer, a delay line, a detector and a feedback control circuit. The feedback control circuit includes a DAC, an ADC and a corresponding data processing algorithm. A small part of the signal enters the Mach-Zehnder interferometer with a delay line, generates a beat frequency signal at the end of the Mach-Zehnder interferometer and is received by the detector; the ADC in the feedback control circuit samples the detection signal and performs software algorithm processing to obtain a nonlinear frequency offset, and thereby calculates the electrical signal compensation value required for each sampling point, and then generates a new electrical signal waveform through the DAC and the signal generator. The electrical signal will be used as the next set of periodic signals and applied to the phase-controlled region for iteration until the output signal linearity meets expectations.

[0013] The present invention aims to provide a linear frequency modulated continuous wave laser calibration method, comprising the following steps:

[0014] S1, laser initialization, fixing the center wavelength of the sweep signal to the microring filter;

[0015] S2: Apply one cycle of electrical signal to the phase-controlled region, thereby outputting one cycle of frequency-modulated continuous wave signal;

[0016] S3. A small portion of the frequency modulated continuous wave signal enters the calibration device through the second direct coupler, and generates a beat frequency signal after passing through the interferometer and the delay line. The detector measures the power spectrum of the beat frequency signal.

[0017] S4. The ADC in the feedback control circuit samples the beat frequency signal, and the software algorithm processes the sampled signal to obtain the nonlinear frequency offset, and calculates the electrical signal compensation value at each sampling point. Let u k+1 (t) = u k (t) + p(t)·e(t), and generate a new electrical signal waveform through DAC and signal generator;

[0018] S5. Repeat steps S2 to S4 until the iterative frequency modulation continuous wave linearity reaches the expected level.

[0019] The purpose of this invention is to propose an algorithm processing flow for linear frequency modulated continuous wave laser calibration, which makes the iterative process more stable, the electrical signal waveform smoother and closer to the theoretical value; the linearity is better, and the effective coverage range is larger. The technical solution adopted is:

[0020] An algorithm processing flow in a linear frequency modulated continuous wave laser calibration process includes the following steps:

[0021] The desired linear frequency modulated continuous wave output frequency within one cycle is set to νd(t), 0<=t<=T, where T is the cycle. In steady state, the voltage required for a frequency change of △G is △V, where △G is the maximum frequency sweep range.

[0022] Step 1: A one-cycle triangular wave electrical signal u(t) is applied to the phase-controlled region to generate a set of swept frequency output signals ν(t);

[0023] Step 2: After the sweep signal passes through the MZI with a delay line, a beat frequency signal is generated at the end with a frequency of f b( t ) = ν ( t+τ ) – ν ( t ), τ is the delay time; the power spectrum of the beat signal is measured by the detector and fed back to the control circuit;

[0024] Step 3: ADC samples the measured power spectrum and performs Hilbert transform on the sampled power spectrum to obtain the instantaneous phase of each sampling point. φ ( t ) = 2π τ · = 2π τ · ν ( t ); from this, the instantaneous frequency ν(t) of each sampling point can be calculated;

[0025] Step 4: Compare the instantaneous frequency with the expected frequency to obtain the frequency difference rms(t), thereby obtaining the voltage compensation value e(t) at each sampling point;

[0026] Step 5. Derivative the instantaneous frequency ν(t) to obtain the slope k(t) of each point, and extract the maximum slope k1 and k2 of the rising edge and falling edge respectively; normalize k(t), set K(t)=k(t) / k1 for the rising edge part and K(t)=k(t) / k2 for the falling edge part, so as to obtain the normalized iteration coefficient p(t)=1-K(t) in the entire cycle;

[0027] Step 6: u k+1 ( t ) = u k ( t ) + p(t) · e ( t );

[0028] Step 7. Repeat steps 1 to 6 until the linearity meets expectations.

[0029] Further optimization of the algorithm processing flow in the linear frequency modulated continuous wave laser calibration process of the present invention, the linearity evaluation function is: , which is the linear regression coefficient, where r is the linearity, , , for average value.

[0030] In summary, the beneficial effects of the present invention are:

[0031] 1. The present invention integrates the calibration device on the silicon photonic external cavity chip, eliminating the need for external placement, thereby improving the integration of the device and reducing costs.

[0032] 2. The algorithm processing flow during the calibration process of the present invention is an adaptive coefficient iterative algorithm, which greatly reduces the electrical signal jumps caused by endpoints and inflection points, thereby effectively avoiding the occurrence of abnormal values in the iteration process, making the iteration process more stable, and the iterated electrical signal smoother and closer to the theoretical value; the linearity is better, and the effective coverage range is larger. At the same time, the adaptive iteration coefficient can improve the iteration efficiency and avoid waste of computing resources.

[0033] 3. The calibration device and algorithm of the present invention are simple and convenient, do not require external devices such as a phase-locked loop, and are highly practical; and the algorithm is an adaptive algorithm, which can effectively avoid the waste of computing resources and achieve rapid iteration. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 1 is a schematic diagram of the structure of a frequency modulated continuous wave laser of an on-chip integrated calibration device according to an embodiment of the present invention;

[0035] Figure 2 is a flow chart of the algorithm processing flow during the calibration process in an embodiment of the present invention;

[0036] Figure 3 This is the simulation result of one iteration of the symmetrical triangular wave electrical signal initialized in the embodiment of the present invention;

[0037] Figure 4 This is the simulation result after initializing the symmetrical triangle wave electrical signal and iterating it 150 times in the embodiment of the present invention;

[0038] Figure 5 is a curve showing the relationship between the linear regression coefficient and the number of iterations in an embodiment of the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clear, the following Figure 1-5 It should be understood that the specific embodiments described herein are only used to illustrate the present invention and are not intended to limit the present invention. Example 1

[0040] like Figure 1As shown, this embodiment is a linear frequency modulated continuous wave laser with an on-chip integrated calibration device, including a gain chip 1 and a silicon photonic external cavity chip 2. The calibration device is integrated on the silicon photonic external cavity chip 2 and is used to evaluate and calculate the response parameters of the frequency modulation nonlinear term to achieve linear output. The silicon photonic external cavity chip 2 sequentially includes: an edge coupler 3, a first direct coupler 4, a phase control region 5 and its heating electrode, a 3dB beam splitter 6, a microring filter 7 and its heating electrode, and a second direct coupler 8. The left and right ends of the gain chip 1 are respectively coated with a high-reflection coating and an anti-reflection coating, and are coupled to the end face of the silicon photonic external cavity chip as a broadband light source. The silicon photonic external cavity chip 2 serves as a laser resonator. Based on the Vernier effect, multiple microrings are used as filters to achieve central wavelength selection. The thermo-optical effect of the silicon material is utilized to change the effective refractive index of the waveguide through the heating electrode to achieve wavelength selection. The phase-controlled region 5 is also based on the thermo-optical effect of silicon materials and is used for precise control of wavelength. That is, by applying an electrical signal to the phase-controlled region, a frequency-modulated continuous wave signal output is achieved. In addition, a calibration device is integrated on the silicon photonic chip. The calibration device includes a Mach-Zehnder interferometer 9, a delay line 10, a detector 11, and a feedback control circuit 12. The Mach-Zehnder interferometer and the delay time are The delay line is located in one arm of the interferometer. The calibration principle is as follows: a signal is applied to the gain chip 1, causing it to spontaneously radiate a broad-spectrum signal light, which then enters the silicon photonic external cavity chip 2 through the edge coupler 3. The signal light then passes through the first direct coupler 4, the phase-controlled region 5, and the 3dB beam splitter 6 before entering the microring filter 7. Utilizing the Vernier effect and the silicon-based thermo-optic effect, by energizing the heating electrode above the microring, the effective refractive index of the waveguide is altered, allowing only signals within the target wavelength and a narrow range to pass through the drop end of the microring and return to the gain chip 1. There, it is reflected back by the high-reflection coating, forming a resonance, thereby determining the center wavelength. A periodic voltage signal is applied to the phase-controlled region 5, generating a small-range swept frequency signal. This signal is transmitted through the direct coupler 1 to the direct coupler 2, with the majority being the output signal, while a smaller portion enters the calibration device. This smaller portion of the signal then passes through a Mach-Zehnder interferometer with a delay line, generating a beat frequency signal at the interferometer end that is received by a detector. The ADC in the feedback control circuit 12 samples the detection signal and processes it with a software algorithm to obtain the nonlinear frequency offset, and thereby calculates the electrical signal compensation value required for each sampling point. A new electrical signal waveform is then generated through the DAC and signal generator. This electrical signal will be used as the next set of periodic signals and applied to the phase-controlled region for iteration until the output signal linearity meets expectations.

[0041] A linear frequency modulated continuous wave laser calibration method comprises the following steps:

[0042] S1, laser initialization, fixing the center wavelength of the sweep signal to the microring filter;

[0043] S2: Apply one cycle of electrical signal to the phase-controlled region, thereby outputting one cycle of frequency-modulated continuous wave signal;

[0044] S3. A small portion of the frequency modulated continuous wave signal enters the calibration device through the second direct coupler, and generates a beat frequency signal after passing through the interferometer and the delay line. The detector measures the power spectrum of the beat frequency signal.

[0045] S4. The ADC in the feedback control circuit samples the beat frequency signal, and the software algorithm processes the sampled signal to obtain the nonlinear frequency offset, and calculates the electrical signal compensation value at each sampling point. Let u k+1 (t) = u k (t) + p(t)·e(t), and generate a new electrical signal waveform through DAC and signal generator;

[0046] S5. Repeat steps S2 to S4 until the iterative frequency modulation continuous wave linearity reaches the expected level.

[0047] like Figure 2 As shown in FIG, the algorithm processing flow during the linear frequency modulated continuous wave laser calibration process includes the following steps:

[0048] The desired linear frequency modulation continuous wave output frequency within one cycle is set to νd(t), 0<=t<=T, and T is the cycle. In steady state, the voltage required for the frequency change △G is △V, where △G is the maximum frequency sweep range.

[0049] Step 1: A one-cycle triangular wave electrical signal u(t) is applied to the phase-controlled region to generate a set of swept frequency output signals ν(t);

[0050] Step 2: After the sweep signal passes through the MZI with a delay line, a beat frequency signal is generated at the end with a frequency of f b( t ) = ν ( t+τ ) – ν ( t ), τ is the delay time; the power spectrum of the beat signal is measured by the detector and fed back to the control circuit;

[0051] Step 3: ADC samples the measured power spectrum and performs Hilbert transform on the sampled power spectrum to obtain the instantaneous phase of each sampling point. φ ( t ) = 2π τ · = 2π τ · ν ( t ); from this, the instantaneous frequency ν(t) of each sampling point can be calculated;

[0052] Step 4: Compare the instantaneous frequency with the expected frequency to obtain the frequency difference rms(t), thereby obtaining the voltage compensation value e(t) at each sampling point;

[0053] Step 5. Derivative the instantaneous frequency ν(t) to obtain the slope k(t) of each point, and extract the maximum slope k1 and k2 of the rising edge and falling edge respectively; normalize k(t), set K(t)=k(t) / k1 for the rising edge part and K(t)=k(t) / k2 for the falling edge part, so as to obtain the normalized iteration coefficient p(t)=1-K(t) in the entire cycle;

[0054] Step 6: u k+1 ( t ) = u k ( t ) + p(t) · e ( t );

[0055] Step 7. Repeat steps 1 to 6 until the linearity meets expectations.

[0056] The linearity evaluation function is: , which is the linear regression coefficient, where r is the linearity, , , for The linearity evaluation function is also known as the linear regression coefficient.

[0057] like Figure 5 As shown, we usually use the linear regression coefficient to evaluate the linearity of the swept laser. Figure 5 The linear regression coefficients of the output frequencies after different numbers of iterations are given. Figure 3 This is the simulation result of one iteration, and its linear regression coefficient is much larger than 10 -4 As the number of iterations increases, the linear regression coefficient gradually decreases. When the number of iterations reaches 150, the curve tends to be saturated and the linear regression coefficient reaches the minimum value, which is close to 10 -8 ,Right now Figure 4 Corresponding simulation results.

[0058] It is known that the nonlinearity primarily originates from the delay associated with the temperature in the phase-controlled region. The differential equation for the temperature response of the phase-controlled region is dT(t) = C*Q(t)+D*(T(t)-T0), where C is the thermal coefficient, Q(t) is the power consumption, D = -C*1 / R / △T, △T is the temperature change caused by a 1V voltage, and T0 is the initial temperature. Based on the response differential equation, the temperature response curve of the phase-controlled region can be derived, thereby determining the temperature change at each moment and the actual voltage change applied to the phase-controlled region. Since the frequency change is proportional to the square of the voltage, the output frequency response can be derived. Based on measured data, in the simulation, we selected C = 70,000 (time units in microseconds), T0 = 25°C, R = 365, and △T = 14.8°C. A voltage squared change of 1.428 results in a frequency change of 3 GHz.

[0059] When the initial input frequency is a linear symmetrical triangle wave voltage signal of 4K, the actual output frequency curve is as follows Figure 3 As shown, we can get the difference between the actual frequency and the expected frequency of each sampling point. Since the frequency is proportional to the square of the voltage, we can get the voltage difference of each sampling point and make up for it according to the iterative algorithm as a group of periodic voltage signals. Figure 4 for Figure 3 The result is the output frequency after 150 iterations of the adaptive algorithm. It can be seen that after 150 iterations, the actual output frequency curve is basically completely consistent with the expected one.

[0060] The above embodiments are only for illustrating the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the present invention.

Claims

1. A linear frequency modulated continuous wave laser calibration method with an on-chip integrated calibration device, characterized by: The steps include: S1, laser initialization, fixing the center wavelength of the sweep signal to the microring filter; S2: Apply one cycle of electrical signal to the phase-controlled region, thereby outputting one cycle of frequency-modulated continuous wave signal; S3. A small portion of the frequency modulated continuous wave signal enters the calibration device through the second direct coupler, and generates a beat frequency signal after passing through the interferometer and the delay line. The detector measures the power spectrum of the beat frequency signal. S4. The ADC in the feedback control circuit samples the beat frequency signal, and the software algorithm processes the sampled signal to obtain the nonlinear frequency offset, and calculates the electrical signal compensation value at each sampling point. Let u k+1 (t) = u k (t) + p(t)·e(t), and generate a new electrical signal waveform through DAC and signal generator; where u k (t) and u k+1 (t) represents the periodic electrical signal after the kth and k+1th iterations, p(t) represents the normalized iteration coefficient, and e(t) represents the voltage compensation value; S5, repeat steps S2 to S4 until the iterative frequency modulation continuous wave linearity reaches the expected value; The linear frequency modulated continuous wave laser comprises a gain chip (1) and a silicon photonic external cavity chip (2); a calibration device is integrated on the silicon photonic external cavity chip (2) and is used to evaluate and calculate the response parameters of the frequency modulation nonlinear term to achieve linear output; an edge coupler (3), a first direct coupler (4), a phase control region (5), a beam splitter (6), a microring filter (7) and a second direct coupler (8) are sequentially arranged on the silicon photonic external cavity chip (2); the edge coupler (3), the first direct coupler (4), the phase control region (5), the beam splitter (6), the microring filter (7) and the second direct coupler (8) are all waveguide structures on the silicon photonic external cavity chip (2) and are all connected by silicon waveguides; The gain chip (1) and the silicon photonic external cavity chip (2) form a laser through end-face coupling, and the edge coupler (3) is connected to the gain chip (1) through end-face coupling. Light is transmitted through the silicon waveguide to the first direct coupler (4) and is divided into two paths. One path of signal light first enters the phase-controlled region (5) along the silicon waveguide, and then is split into two by the beam splitter (6) and enters the micro-ring filter (7) and then recombines and returns to the original path; the other path of signal light propagates along another silicon waveguide to the second direct coupler (8), and is then divided into two paths of light. Most of the signal light is output from the out end as an output signal, and a small part of the signal is transmitted to the calibration device via the silicon waveguide.

2. The linear frequency modulated continuous wave laser calibration method of the on-chip integrated calibration device according to claim 1, characterized in that: Both ends of the gain chip (1) are coated with a high reflection film and an anti-reflection film respectively.

3. The linear frequency modulated continuous wave laser calibration method of the on-chip integrated calibration device according to claim 1, characterized in that: The phase-controlled region (5) is composed of a silicon waveguide and a heating electrode thereon.

4. The linear frequency modulated continuous wave laser calibration method of the on-chip integrated calibration device according to claim 1, characterized in that: The micro-ring filter (7) is composed of a plurality of micro-rings and heating electrodes thereon.

5. The linear frequency modulated continuous wave laser calibration method of the on-chip integrated calibration device according to claim 1, characterized in that: The first direct coupler (4) has a 1x2 structure, and the second direct coupler (8) has a splitting ratio of 9:

1. Most of the light is output from the out end as an output signal, and a small part of the light is transmitted to the calibration device through the silicon waveguide as a calibration signal.

6. The linear frequency modulated continuous wave laser calibration method of the on-chip integrated calibration device according to claim 1, characterized in that: The calibration device includes a Mach-Zehnder interferometer (9), a delay line (10), a detector (11) and a feedback control circuit (12). The feedback control circuit (12) includes a DAC, an ADC and a corresponding data processing algorithm. A small portion of the signal enters the Mach-Zehnder interferometer (9) with the delay line (10), and a beat frequency signal is generated at the end of the Mach-Zehnder interferometer (9) and received by the detector (11); the ADC in the feedback control circuit (12) samples the detection signal and processes it with a software algorithm to obtain a nonlinear frequency offset, and thereby calculates the electrical signal compensation value required for each sampling point, and then generates a new electrical signal waveform through the DAC and the signal generator. The electrical signal will be used as the next set of periodic signals and applied to the phase-controlled region for iteration until the output signal linearity meets expectations.

7. The linear frequency modulated continuous wave laser calibration method of the on-chip integrated calibration device according to claim 1, characterized in that: The algorithm processing flow in the linear frequency modulated continuous wave laser calibration process is characterized by comprising the following steps: The desired linear frequency modulated continuous wave output frequency within one cycle is set to νd(t), 0<=t<=T, where T is the cycle. In steady state, the voltage required for a frequency change of △G is △V, where △G is the maximum frequency sweep range. Step 1: A one-cycle triangular wave electrical signal u(t) is applied to the phase-controlled region to generate a set of swept frequency output signals ν(t); Step 2: After the sweep signal passes through the MZI with a delay line, a beat frequency signal is generated at the end with a frequency of f b( t ) = ν ( t+ τ ) – ν ( t ), τ is the delay time; the power spectrum of the beat signal is measured by the detector and fed back to the control circuit; Step 3: ADC samples the measured power spectrum and performs Hilbert transform on the sampled power spectrum to obtain the instantaneous phase of each sampling point. φ ( t ) = 2π τ · = 2π τ · ν ( t ); from this, the instantaneous frequency ν(t) of each sampling point can be calculated; Step 4: Compare the instantaneous frequency with the expected frequency to obtain the frequency difference rms(t), thereby obtaining the voltage compensation value e(t) at each sampling point; Step 5. Derivative the instantaneous frequency ν(t) to obtain the slope k(t) of each point, and extract the maximum slope k1 and k2 of the rising edge and falling edge respectively; normalize k(t), set K(t)=k(t) / k1 for the rising edge part and K(t)=k(t) / k2 for the falling edge part, so as to obtain the normalized iteration coefficient p(t)=1-K(t) in the entire cycle; Step 6: u k+1 ( t ) = u k ( t ) + p(t) · e ( t ); Step 7. Repeat steps 1 to 6 until the linearity meets expectations.

8. The algorithm processing flow in the linear frequency modulated continuous wave laser calibration process according to claim 7, characterized in that: The linearity evaluation function is: , where r is the linearity, , , for average value.

Images