Frequency-modulated light source, method for modulating optical signal, and lidar

Abstract

The present disclosure provides a frequency-modulated light source, a method for modulating an optical signal, and a lidar. The frequency-modulated light source comprises a laser, a frequency discrimination circuit, and a first feedback circuit. The laser is configured to emit frequency-modulated light. The frequency discrimination circuit is coupled to the laser and configured to output a frequency discrimination signal. An input terminal of the first feedback circuit is coupled to the frequency discrimination circuit. An output terminal of the first feedback circuit is coupled to the laser. The first feedback circuit is configured to output a first feedback signal on the basis of the frequency discrimination signal and a first reference signal, so as to adjust the linearity of the frequency-modulated light.

Description

Frequency modulation light source, method of modulating optical signal and lidar

[0001] This disclosure claims priority to Chinese Patent Application No. 202412000002.7, filed on December 31, 2024, entitled "Circuit for Emitting Linear Frequency Modulated Light and LiDAR", and Chinese Patent Application No. 20241200002.X, filed on December 31, 2024, entitled "Method for Modulating Optical Signals, Frequency Modulated Light Source and FMCW LiDAR", the contents of which are incorporated herein by reference in their entirety. Technical Field

[0002] This disclosure relates to the field of lidar technology, and more particularly to a frequency-modulated light source, a method for modulating optical signals, and a lidar. Background Technology

[0003] Frequency Modulated Continuous Wave (FMCW) lidar typically requires a linearly frequency-modulated light source with high coherence and high power. The frequency of the detection signal of an FMCW lidar changes linearly with time, and the time of flight (TOF) or velocity of an object can be accurately obtained based on the frequency shift.

[0004] In lidar, the operating environment of the light source is affected by factors such as uneven stress and tension, circuit noise, and temperature variations within the laser cavity. Existing frequency-modulated light sources may struggle to output highly linear frequency-modulated light. The nonlinear deviation of the linear frequency-modulated light can easily lead to a decrease in the ranging accuracy and resolution of FMCW lidar, thus reducing its reliability.

[0005] Improving the linearity of frequency-modulated light has become a challenge. Summary of the Invention

[0006] This disclosure provides an embodiment of a frequency-modulated light source that can emit frequency-modulated light with high linearity.

[0007] In a first aspect, embodiments of this disclosure provide a frequency-modulated light source, including: a laser, a frequency discrimination circuit, and a first feedback circuit. The laser is configured to emit frequency-modulated light. The frequency discrimination circuit is coupled to the laser and configured to output a frequency discrimination signal. The input terminal of the first feedback circuit is coupled to the frequency discrimination circuit, and its output terminal is coupled to the laser. The first feedback circuit is configured to output a first feedback signal based on the frequency discrimination signal and a first reference signal to adjust the linearity of the frequency-modulated light.

[0008] Optionally, the first feedback circuit includes a subtractor and a PID controller. The subtractor is configured to output an error signal based on the frequency discrimination signal and a first reference signal. The PID controller is coupled to the subtractor and configured to receive the error signal and output a first feedback signal.

[0009] Optionally, the frequency discrimination circuit includes: a frequency discriminator; and a phase modulation circuit. The phase modulation circuit is coupled to the frequency discriminator and configured to adjust the operating point of the frequency discriminator based on a second feedback signal.

[0010] Optionally, the frequency-modulated light source also includes a second feedback circuit. The second feedback circuit is coupled to the frequency discrimination circuit and configured to receive the frequency discrimination signal and the second reference signal, and output the second feedback signal to the phase modulation circuit to adjust the operating point of the frequency discrimination circuit.

[0011] Optionally, the second feedback circuit includes at least one of the following: an analog signal processing circuit; or a digital signal processing circuit.

[0012] Optionally, the analog signal processing circuit includes a multiplier and a filter. The multiplier is configured to output a phase detection signal based on the frequency discrimination signal and a second reference signal. The filter is coupled to the multiplier and configured to receive the phase detection signal and output a second feedback signal.

[0013] Optionally, the digital signal processing circuit is configured to perform at least one of Hilbert transform and sine signal fitting on the frequency discrimination signal to determine the second feedback signal.

[0014] Optionally, the frequency discriminator includes at least one of the following: a Mach-Zehnder interferometer, a fiber Bragg grating, a bandpass filter, a Fabry-Perot resonator, or a microring.

[0015] Optionally, the phase modulation circuit includes at least one of the following: a phase modulator, a semiconductor optical amplifier, a piezoelectric ceramic, a thermally modulated phase shifter, or an electrically modulated phase shifter.

[0016] Optionally, the frequency discriminator circuit further includes a balanced detection circuit. The input of the balanced detection circuit is coupled to the frequency discriminator, and the output of the balanced detection circuit is coupled to the first feedback circuit and the second feedback circuit.

[0017] Optionally, the balanced detection circuit includes a first photodetector and a second photodetector. The anode of the first photodetector is coupled to the cathode of the second photodetector. The first and second photodetectors are configured to convert an optical signal into an electrical signal.

[0018] Secondly, embodiments of this disclosure provide a frequency-modulated light source, including: a laser, a frequency discrimination circuit, and a first feedback circuit. The laser is configured to emit frequency-modulated light. The frequency discrimination circuit is coupled to the laser and configured to output a frequency discrimination signal. The input terminal of the first feedback circuit is coupled to the frequency discrimination circuit, and its output terminal is coupled to the laser. The first feedback circuit includes a calculation unit. The calculation unit is configured to output a first feedback signal based on the frequency discrimination signal and demodulation parameters to adjust the linearity of the frequency-modulated light.

[0019] Thirdly, this disclosure provides a method for modulating an optical signal, comprising: receiving a first signal obtained by converting a first optical signal; extracting a first sub-signal and a second sub-signal from the first signal based on demodulation parameters; performing orthogonal demodulation processing based on the first sub-signal and the second sub-signal to obtain a plurality of demodulated signals to determine a first feedback signal; and modulating light based on the first feedback signal.

[0020] Optionally, the step of extracting the first sub-signal and the second sub-signal from the first signal based on the demodulation parameters includes: determining the first sub-signal based on the first demodulation parameters; determining the second sub-signal based on the second demodulation parameters; wherein the first demodulation parameters and the second demodulation parameters are different.

[0021] Optionally, the angular frequency of the second demodulation parameter is twice the angular frequency of the first demodulation parameter.

[0022] Optionally, the step of performing quadrature demodulation processing based on the first sub-signal and the second sub-signal to obtain multiple demodulated signals and determine the first feedback signal includes: removing the high-frequency component of the first sub-signal to obtain a first filtered signal; removing the high-frequency component of the second sub-signal to obtain a second filtered signal; determining the multiple demodulated signals based on the phase information of the first filtered signal and the second filtered signal; and determining the first feedback signal based on the multiple demodulated signals.

[0023] Optionally, the step of removing the high-frequency components of the first sub-signal to obtain the first filtered signal includes: performing low-pass filtering on the first sub-signal to obtain the first filtered signal; the step of removing the high-frequency components of the second sub-signal to obtain the second filtered signal includes: performing low-pass filtering on the second sub-signal to obtain the second filtered signal.

[0024] Optionally, the step of determining the plurality of demodulated signals based on the phase information of the first filtered signal and the second filtered signal includes: obtaining the phase information of the filtered signal through differentiation processing, wherein the filtered signal is one of the first filtered signal and the second filtered signal.

[0025] Optionally, the step of determining the plurality of demodulated signals based on the phase information of the first filtered signal and the second filtered signal further includes: obtaining a first demodulated signal based on the phase information of the first filtered signal and the second filtered signal; and obtaining a second demodulated signal based on the phase information of the second filtered signal and the first filtered signal.

[0026] Optionally, the step of determining the first feedback signal based on the plurality of demodulated signals includes: eliminating the common component of the two demodulated signals; and determining the first feedback signal based on the result after eliminating the common component of the two demodulated optical signals.

[0027] Optionally, in the step of eliminating the common component of the two demodulated optical signals, the two demodulated optical signals are subtracted to eliminate the common component of the two demodulated optical signals.

[0028] Optionally, in the step of determining the first feedback signal based on the result after eliminating the common component of the two demodulated optical signals, the result after eliminating the common component of the two demodulated optical signals is integrated to generate the first feedback signal.

[0029] Optionally, the step of determining the first feedback signal based on the plurality of demodulated signals further includes: performing noise reduction processing on the first feedback signal; and in the step of modulating the light according to the first feedback signal, modulating the light according to the noise-reduced first feedback signal.

[0030] Optionally, in the step of denoising the first feedback signal, the low-frequency component and DC component of the first feedback signal are removed, and the high-frequency component of the feedback signal is retained to obtain the denoised feedback signal.

[0031] Optionally, in the step of denoising the first feedback signal, the first feedback signal is subjected to high-pass filtering.

[0032] Optionally, the method for modulating an optical signal further includes: receiving a second optical signal, the second optical signal including at least a portion of an initial optical signal or an initial modulated optical signal formed by modulating the initial optical signal; converting the second optical signal into a first optical signal; performing photoelectric conversion on the first optical signal to obtain a first electrical signal; and sampling the first electrical signal to obtain the first signal.

[0033] Fourthly, this disclosure also provides a frequency-modulated light source, comprising: a laser, a frequency discrimination circuit, a first feedback circuit, and a driving circuit. The laser is configured to generate an initial optical signal. The frequency discrimination circuit is configured to receive a second optical signal and convert the frequency information of the second optical signal into the light intensity information of a first optical signal. The second optical signal includes at least a portion of the initial optical signal or an initial frequency-modulated optical signal formed by modulating the initial optical signal. The first feedback circuit is configured to receive a first signal obtained by converting the first optical signal. The first feedback circuit is further configured to extract a first sub-signal and a second sub-signal from the first signal based on demodulation parameters. The first feedback circuit is further configured to perform quadrature demodulation processing based on the first sub-signal and the second sub-signal to obtain multiple demodulated signals, and determine a first feedback signal based on the multiple demodulated signals. The driving circuit is configured to modulate light based on the first feedback signal.

[0034] Fifthly, embodiments of this disclosure provide a lidar including a frequency-modulated light source from any of the above embodiments.

[0035] Sixthly, this disclosure also provides an FMCW lidar, comprising: a frequency-modulated light source, a receiving component, and a processor. The frequency-modulated light source is the frequency-modulated light source of this disclosure. The frequency-modulated light source is configured to generate local oscillator light and probe light. The probe light is emitted outside the lidar. The probe light is reflected by an object to form an echo light. The receiving component is configured to receive the echo light. The processor is configured to obtain at least one of the distance and velocity of the object based on the local oscillator light and the echo light. Attached Figure Description

[0036] Figure 1 shows a structural example of an FMCW lidar.

[0037] Figure 2 shows an example spectrum of the local oscillator light and echo light of an FMCW lidar.

[0038] Figure 3 shows an example diagram of a frequency-modulated light source according to the present disclosure.

[0039] Figure 4 shows an example of the transmittance curve of a frequency discriminator according to the present disclosure.

[0040] Figure 5 shows an example diagram of the frequency-amplitude conversion result of a frequency discriminator of the present disclosure, wherein sub-Figure 5a shows an example diagram of the frequency change of the laser, and sub-Figure 5b shows an example diagram of the amplitude change of the discriminator signal corresponding to the frequency change of the laser shown in sub-Figure 5a.

[0041] Figure 6 shows an example diagram of a Mach-Zehnder interferometer of this disclosure.

[0042] Figure 7 shows an example diagram of a frequency discrimination circuit of this disclosure.

[0043] Figure 8 shows an example diagram of a phase modulation circuit of this disclosure.

[0044] Figure 9 shows an example diagram of a frequency discrimination circuit of this disclosure.

[0045] Figure 10 shows an example diagram of a first feedback circuit of this disclosure.

[0046] Figure 11 shows an example diagram of a balanced detection circuit of this disclosure.

[0047] Figure 12 shows an example diagram of a frequency-modulated light source according to the present disclosure.

[0048] Figure 13 shows an example diagram of a first feedback circuit of this disclosure.

[0049] Figure 14 shows an example diagram of a frequency-modulated light source according to the present disclosure.

[0050] Figure 15 shows a schematic flowchart of some embodiments of the method for modulating optical signals according to the present disclosure.

[0051] Figure 16 shows a schematic flowchart of some embodiments of the method for modulating optical signals according to the present disclosure.

[0052] Figure 17 shows a schematic flowchart of some embodiments of the method for modulating optical signals according to the present disclosure.

[0053] Figure 18 shows a schematic flowchart of some embodiments of the method for modulating optical signals according to the present disclosure.

[0054] Figure 19 shows a schematic flowchart of some embodiments of the method for modulating optical signals according to the present disclosure.

[0055] Figure 20 shows an example diagram of a frequency-modulated light source according to the present disclosure.

[0056] Figure 21 shows an example diagram of a frequency-modulated light source according to the present disclosure. Detailed Implementation

[0057] The operating environment of the light source is affected by factors such as uneven stress and tension, circuit noise, and temperature variations within the laser cavity. Existing frequency-modulated lasers may struggle to output highly linear frequency-modulated light. The nonlinear deviation of the linear frequency-modulated light can easily lead to a decrease in the ranging accuracy and resolution of FMCW lidar, thus reducing its reliability.

[0058] The following is a brief introduction to linear frequency modulated light based on the detection principle of FMCW lidar.

[0059] Figure 1 shows a structural example of an FMCW lidar. Referring to Figure 1, the FMCW lidar 100 includes a laser 102 and a detector 104. The FMCW lidar 100 can generate laser light through the laser 102. The laser light can be linearly frequency modulated (LFM) light. A portion of the LFM light is emitted into external space as probe light, and another portion is transmitted to the detector 104 as local oscillator light. The probe light is reflected by an object O to obtain echo light. This echo light is also transmitted to the detector 104. The local oscillator light and the echo light are beat-frequencyd to obtain their beat frequency signals. Relevant information about the object can be determined based on the beat frequency signals. For example, one or more parameters such as the object's distance, flight time, and speed.

[0060] Figure 2 shows an example spectrum of the local oscillator light and echo light of an FMCW lidar. For example, referring to Figure 2, the frequencies of the local oscillator light and echo light change linearly with time. The variation pattern is, for example, a triangular wave. Based on the beat frequency signals of the local oscillator light and echo light, the distance information of the obstacle can be obtained according to the following formula (1): D=(fb*c*ts) / (2Δf) (1)

[0061] In the formula, fb represents the frequency of the beat frequency signal of the local oscillator and the probe echo signal. c represents the speed of light. ts represents the period of the probe light signal sweep. Δf represents the frequency modulation bandwidth of the probe light signal sweep.

[0062] When there is a relative velocity between the object and the FMCW lidar, the velocity of the object can also be obtained from the beat frequency signal.

[0063] The frequency of the probe light changes linearly with time, which can improve the accuracy of the acquired detection information. Achieving a preset linearity requirement for the probe light is beneficial for obtaining accurate detection information.

[0064] The application environment of lasers in lidar faces challenges such as uneven stress and tension, circuit noise, and temperature variations within the laser cavity. Existing frequency-modulated lasers often struggle to output highly linear frequency-modulated light. Improving the linearity of frequency-modulated light is crucial for enhancing the detection accuracy and reliability of FMCW lidar.

[0065] This disclosure provides a frequency-modulated light source. The frequency-modulated light source includes a laser, a frequency discrimination circuit, and a first feedback circuit. The laser can emit frequency-modulated light. The frequency discrimination circuit is coupled to the laser and can output a frequency discrimination signal. The input terminal of the first feedback circuit is coupled to the frequency discrimination circuit, and the output terminal is coupled to the laser. The first feedback circuit can output a first feedback signal based on the frequency discrimination signal and a first reference signal. The first feedback signal can adjust the linearity of the frequency-modulated light to improve linearity.

[0066] Figure 3 shows an example diagram of a frequency-modulated light source according to the present disclosure. Referring to Figure 3, in some embodiments, the frequency-modulated light source 300 may include a laser 302, a frequency discrimination circuit 304, and a first feedback circuit 306.

[0067] Laser 302 can emit frequency-modulated light. The frequency-modulated light is, for example, linearly frequency-modulated light. The frequency of linearly frequency-modulated light changes linearly with time. The change can take the form of a triangular wave, sawtooth wave, trapezoidal wave, etc.

[0068] For example, continuing to refer to Figure 3, the frequency-modulated light emitted by laser 302 is split into Out1 and Out2 by a coupler (not shown in the figure). Out1 serves as a probe light and can be emitted into external space for object detection. Out2 serves as a detection light and is transmitted to the frequency discriminator circuit 304.

[0069] In some embodiments, laser 302 may include, but is not limited to, fiber lasers, distributed feedback lasers (DFBLs), distributed Bragg reflector lasers (DBRLs), or vertical-cavity surface-emitting lasers (VCSELs).

[0070] It is understood that the embodiments disclosed herein do not impose specific limitations on the laser, and the above embodiments are merely illustrative examples.

[0071] The frequency discrimination circuit 304 is coupled to the laser 302. The frequency discrimination circuit 304 can receive the detection light Out2 and output the frequency discrimination signal S. f .

[0072] In some embodiments, the frequency discrimination circuit 304 may include a frequency discriminator (not shown in the figure).

[0073] The input of the frequency discriminator receives the detection light Out2. The output of the frequency discriminator outputs the discriminated light signal.

[0074] The frequency of the linearly frequency-modulated light emitted by the laser can be quantized as f = f0 + kt + δ. In this formula, f0 is the initial frequency of the laser, k is the frequency modulation slope of the linearly frequency-modulated light, and δ is the frequency modulation nonlinear parameter that needs to be adjusted.

[0075] Figure 4 shows an example of the transmittance curve of a frequency discriminator according to this disclosure. Referring to Figure 4, the initial frequency f0 of the laser is located at the full width at half maximum (FWHM) of the transmission peak of the frequency discriminator. The FWHM of the transmission peak corresponds to an operating point of the frequency discriminator. When the frequency of the laser changes with time, the frequency discriminator can convert the frequency change into an amplitude change. Referring to Figure 4, the frequency of the light becomes f2 at the first moment and f1 at the second moment. The frequency discriminator is very sensitive to changes in the frequency of the light. Even a small change in the frequency of the light can cause a significant change in the amplitude of the discriminator's output frequency-discrimination signal. For example, Figure 5 shows an example of the frequency-amplitude conversion result of a frequency discriminator according to this disclosure. Referring to sub-Figure 5a of Figure 5, the frequency of the laser emitted light changes around f0. Referring to sub-Figure 5b of Figure 5, correspondingly, the amplitude of the frequency-discrimination signal changes around the value P0. The amplitude change of the frequency-discrimination signal is significantly greater than the amplitude change of the light frequency.

[0076] In some embodiments, the frequency discriminator may include at least one of a Mach-Zehnder interferometer, a fiber Bragg grating, a bandpass filter, a Fabry-Perot resonator, or a microring.

[0077] For example, Figure 6 shows an example diagram of a Mach-Zehnder interferometer of this disclosure. Referring to Figure 6, the Mach-Zehnder interferometer 600 may include coupler 602, coupler 604, waveguide arm 606, and waveguide arm 608. Waveguide arm 606 and waveguide arm 608 have different optical path lengths.

[0078] When the detection light Out2 is transmitted to coupler 602, it is split into two paths. One path enters waveguide arm 606, and the other enters waveguide arm 608. The optical path length of waveguide arm 606 is greater than that of waveguide arm 608. The light transmitted through waveguide arm 606 is delayed. An optical path difference (i.e., phase difference) is generated between the two paths transmitted through waveguide arms 606 and 608. The two paths are coherently coupled at coupler 604 and combined into a single output beam. The frequency discriminator 600 outputs the frequency-discriminated optical signal S. f′ The amplitude of the detection light and the frequency of the detection light have the relationship shown in Figure 4. The frequency of the detection light can be determined by detecting the amplitude of the frequency-discriminating light signal, thus realizing frequency discrimination of the detection light Out2.

[0079] In some embodiments, the frequency-modulated light source of this disclosure includes a frequency discriminator and a phase modulation circuit. The phase modulation circuit is coupled to the frequency discriminator and adjusts the operating point of the frequency discriminator based on a second feedback signal. The phase modulation circuit can keep the operating point of the frequency discriminator consistent with the real-time frequency of the frequency-modulated light. In this way, the frequency of the frequency-modulated light can be stably located at the operating point of the frequency discriminator, improving the accuracy of the first feedback signal.

[0080] Figure 7 shows an example diagram of a frequency discrimination circuit according to the present disclosure. Referring to Figure 7, in some embodiments, the frequency discrimination circuit 700 may include a frequency discriminator 702 and a phase modulation circuit 704.

[0081] The input of frequency discriminator 702 receives the detection light Out2. The output of frequency discriminator 702 outputs the discriminated optical signal S. f′ .

[0082] The phase modulation circuit 704 is coupled to the frequency discriminator 702. The phase modulation circuit 704 can adjust the operating point of the frequency discriminator 702.

[0083] The modulation signal of the phase modulation circuit 704 to the frequency discriminator 702 can correspond to the modulation signal of the laser. For example, the modulation signal of the laser causes the frequency of the frequency-modulated light emitted by the laser to change linearly with time. The modulation signal of the frequency discriminator causes the operating point of the frequency discriminator to change linearly with time. The frequency corresponding to the operating point of the frequency discriminator 702 is consistent with the instantaneous frequency of the frequency-modulated light emitted by the laser.

[0084] In some embodiments, the phase modulation circuit 704 may include a phase modulator.

[0085] For example, Figure 8 shows an example diagram of a phase modulation circuit of the present disclosure. Referring to Figure 8, in some embodiments, the phase modulation circuit 800 may include electrodes 802 and 804. The phase modulation circuit 800 may apply a phase that varies linearly with voltage to the input optical field according to the following formula (2) to adjust the operating point of the frequency discriminator.

[0086] In the formula, For phase. α EO λ is the electro-optic coefficient. L is the electrode length. d is the distance between electrodes 1002 and 1004. λ is the wavelength of the input light. V is the applied voltage.

[0087] In some embodiments, the phase modulation circuit may include a semiconductor optical amplifier.

[0088] For example, the phase of the optical signal can be adjusted by regulating the injection current of the semiconductor optical amplifier, thereby adjusting the operating point of the frequency discriminator.

[0089] In some embodiments, the phase modulation circuit may include piezoelectric ceramics.

[0090] For example, the phase of an optical signal can be adjusted by regulating the modulation voltage applied to the piezoelectric ceramic, thereby adjusting the operating point of the frequency discriminator.

[0091] In some embodiments, the phase modulation circuit may include a thermally modulated phase shifter.

[0092] For example, a thermally modulated phase shifter can adjust the phase of an optical signal by changing the temperature, thereby adjusting the operating point of the frequency discriminator.

[0093] In some embodiments, the phase modulation circuit may include an electrically tunable phase shifter.

[0094] For example, an electrically tunable phase shifter can adjust the phase of an optical signal by adjusting the electrical signal it applies to the optical path, thereby adjusting the operating point of the frequency discriminator.

[0095] Figure 9 shows an example diagram of a frequency discrimination circuit according to the present disclosure. Referring to Figure 9, in some embodiments, the frequency discrimination circuit 900 includes a Mach-Zehnder interferometer 910 and an electrically tunable phase shifter 920. The Mach-Zehnder interferometer 910 includes couplers 912 and 914, waveguide arm 916, and waveguide arm 918. The optical path lengths of waveguide arm 916 and waveguide arm 918 are not the same.

[0096] An electrically tunable phase shifter 920 can be mounted on the waveguide arm 918. The electrically tunable phase shifter 920 controls the refractive index of the waveguide arm 918 by applying an external electric field. Adjusting the magnitude of the electric field changes the refractive index of the waveguide arm 918, thereby changing the phase of the light transmitted through the waveguide arm 918 and adjusting the operating point of the Mach-Zehnder interferometer 910.

[0097] In some embodiments, the frequency discriminator may include a microring.

[0098] For example, a frequency discriminator may include a single-waveguide-coupled microring. The single-waveguide-coupled microring consists of a ring waveguide and a straight waveguide. When the frequency of the input optical signal meets the resonance condition, the optical signal interferes and is enhanced within the microring, reducing the coupling strength with the straight waveguide and decreasing the output light intensity. When the frequency of the input light matches the resonant frequency of the microring, the optical signal within the microring interferes and is enhanced, a large amount of light energy is absorbed by the microring, and the output light intensity is minimal. When the frequency of the input light deviates from the resonant frequency, the resonance effect weakens, and the output light intensity gradually increases. The output light intensity is related to the frequency of the input light. By measuring the output light intensity of the microring, the frequency of the input light can be determined based on the relationship between the output light intensity and the input light frequency.

[0099] In some embodiments, the frequency discriminator may include fiber Bragg gratings (FBG).

[0100] For example, FBG can be used for optical signals of a specific wavelength (i.e., the Bragg wavelength λ). B It has a strong reflective effect. For a specific FBG, when the wavelength corresponding to the incident light frequency is close to λ... B At this time, the reflected light intensity is close to its maximum value. When the wavelength corresponding to the incident light frequency is far from λ... BWhen the intensity of reflected light decreases, the intensity of transmitted light increases. The intensity of reflected or transmitted light detected at the output of the FBG is related to the frequency of the incident light. Based on the relationship between the intensity of reflected or transmitted light and the frequency of the incident light, the frequency of the incident light can be determined by detecting the intensity of reflected or transmitted light.

[0101] In some embodiments, the frequency discriminator may include a bandpass filter.

[0102] For example, a bandpass filter allows optical signals within a certain frequency range to pass through, while attenuating optical signals outside that range. The frequency at which a bandpass filter provides maximum gain for the passed optical signal is its center frequency f. c When the frequency of the input optical signal is close to the center frequency f of the bandpass filter. c At a certain frequency, the optical signal transmission efficiency is highest, and the output signal amplitude is largest. When the input optical signal frequency is far from f... c When the bandpass filter attenuates the optical signal more, the amplitude of the output light decreases. The amplitude of the output optical signal varies with the frequency of the input optical signal; the magnitude of the amplitude reflects the deviation of the input light frequency from f. c The degree of intensity. By detecting changes in the amplitude of the output optical signal, the frequency information of the input optical signal can be obtained.

[0103] In some embodiments, the frequency discriminator may include a Fabry-Perot resonator.

[0104] Fabry-Perot resonators utilize resonant characteristics to selectively respond to optical signals at frequencies. By measuring the light intensity within the resonator, it can be determined whether the frequency of the input optical signal meets the resonant condition of the cavity, thus achieving frequency discrimination.

[0105] It is understood that the embodiments disclosed herein do not impose specific limitations on the frequency discriminator.

[0106] Referring again to Figure 3, the input of the first feedback circuit 306 is coupled to the frequency discriminator circuit 304. The output is coupled to the laser 302. The first feedback circuit 306 can be based on the frequency discriminator signal S. f With the first reference signal S r1 Output the first feedback signal S b1 First feedback signal S b1 It can be used to adjust the linearity of the light produced by the frequency-modulated laser 302.

[0107] For example, a frequency-modulated light source may include a directly modulated laser. The emission frequency of the laser can be adjusted by regulating the drive current. The linearity of the frequency-modulated light can be adjusted based on a first feedback signal. Exemplarily, a current regulating element can be provided to regulate the drive current of the laser.

[0108] For example, a frequency-modulated light source also includes a modulator. A laser can generate fixed-frequency light. The modulator modulates the fixed-frequency light to generate frequency-modulated light. The frequency of the frequency-modulated light can be adjusted by adjusting the input electrical signal of the modulator. In this case, the linearity of the frequency-modulated light can be adjusted based on a first feedback signal. Exemplarily, the modulator may include a voltage-controlled oscillator (VCO) and a voltage regulation element. The frequency of the frequency-modulated light is adjusted by regulating the input voltage of the VCO.

[0109] Figure 10 shows an example diagram of a first feedback circuit according to the present disclosure. Referring to Figure 10, in some embodiments, the first feedback circuit 1000 includes a subtractor 1002 and a PID controller 1004.

[0110] The first input terminal of the subtractor 1002 is coupled to the frequency discriminator and can receive the frequency discrimination signal S. f The second input of subtractor 1002 can receive the first reference signal S. r1 Subtractor 1002 can be based on the frequency discrimination signal S. f With the first reference signal S r1 Output error signal S e .

[0111] In some embodiments, the first reference signal S r1 It can be generated by a sinusoidal oscillator. For example, the first reference signal S r1 It can be the frequency discrimination signal output by the frequency-modulated light that meets the preset linearity requirements after passing through the frequency discrimination circuit.

[0112] In some embodiments, the subtractor 1002 may include a differential amplifier. The first input of the differential amplifier receives a frequency discrimination signal S. f The second input terminal of the differential amplifier receives the first reference signal S. r1 After passing through the differential amplifier, the output terminal of the differential amplifier outputs an error signal S. e .

[0113] The PID controller 1004 is coupled to the subtractor 1002. The PID controller 1004 can receive the error signal S. e Output the first feedback signal S b1 .

[0114] A PID controller processes error signals through a combination of proportional, integral, and derivative control actions to achieve precise control of the target value. For example, a PID controller, based on the error signal S... e Calculate the outputs of the proportional, derivative, and integral components. Combine the outputs of the three components into a control signal, which serves as the first feedback signal S. b1 Output.

[0115] In some embodiments, the frequency discrimination circuit may further include a balanced detection circuit. The input of the balanced detection circuit is coupled to the frequency discriminator. The output of the balanced detection circuit is coupled to a first feedback circuit and a second feedback circuit. The balanced detection circuit can perform photoelectric conversion, converting the frequency-discriminating optical signal output by the frequency discriminator into the frequency-discriminating signal.

[0116] For example, Figure 11 shows an example diagram of a balanced detection circuit of the present disclosure. Referring to Figure 11, in some embodiments, the balanced detection circuit 1100 may include a first photodetector 1102 and a second photodetector 1104. The anode of the first photodetector 1102 is coupled to the cathode of the second photodetector 1104. The first photodetector 1102 and the second photodetector 1104 can convert optical signals into electrical signals.

[0117] Frequency discrimination optical signal S f′ The signal can be divided into two equal parts. The two discriminator optical signals are received by the first photodetector 1102 and the second photodetector 1104, respectively. The first photodetector 1102 and the second photodetector 1104 are connected in series. The DC components of the currents generated by the two photodetectors are the same, while the AC components are opposite. The currents generated by the two photodetectors are combined to form the discriminator signal S. f The output can eliminate the DC component in the current and suppress common-mode signals.

[0118] Figure 12 shows an example diagram of a frequency-modulated light source according to the present disclosure. Referring to Figure 12, the laser 1210 emits frequency-modulated light under the modulation of a modulation signal. The emitted frequency-modulated light is split into Out1 and Out2 by a coupler (not shown). Out1 serves as a probe light and can be used to determine relevant information about objects in the probe space. Out2 serves as a detection light and can be input to the frequency discrimination circuit 1220.

[0119] In some embodiments, the frequency discriminator circuit 1220 may include a frequency discriminator 1222 and a phase modulator 1224. As shown in FIG12, the frequency discriminator 1222 includes a Mach-Zehnder interferometer 1222. The Mach-Zehnder interferometer 1222 may include a coupler 12222, a coupler 12224, a waveguide arm 12226, and a waveguide arm 12228. The optical path lengths of waveguide arm 12226 and waveguide arm 12228 are not the same. The phase modulator 1224 may be disposed on waveguide arm 12228.

[0120] Frequency discriminator 1222 performs frequency discrimination processing on the detection light Out2 to obtain the frequency-discriminated optical signal S. f′ Frequency discrimination optical signal S f′ It is transmitted to the balance detection circuit 1226.

[0121] In some embodiments, coupler 12222 and coupler 12224 are 1:1 couplers. Based on the transmission matrix of the Mach-Zehnder interferometer, the frequency-discriminating optical signal S can be obtained. f′ The two optical signals S after being split by coupler 12224 f′1 and S f′2 It can be expressed by the following formulas (3) and (4).

[0122] In the formula, P in The input frequency-modulated light is denoted by f0. The initial frequency of the laser is denoted by f0. The frequency modulation slope of the linearly frequency-modulated light is denoted by k. The frequency modulation nonlinearity deviation to be adjusted is δ. The delay difference between the two waveguide arms of the Mach-Zehnder interferometer is denoted by τ. This represents the operating phase of the Mach-Zehnder interferometer. The phase component of the operating point that needs adjustment.

[0123] In some embodiments, the balanced detection circuit 1226 may include a first photodetector 12262 and a second photodetector 12264. The first photodetector 12262 and the second photodetector 12264 are connected in series. Exemplarily, the first photodetector 12262 and the second photodetector 12264 operate at the same voltage. Alternatively, the first photodetector 12262 and the second photodetector 12264 have the same gain.

[0124] The output terminal of the balanced detection circuit 1226 is located between the first photodetector 12262 and the second photodetector 12264. The currents generated by the first photodetector 12262 and the second photodetector 12264 are combined into a frequency discrimination signal S. f Frequency discrimination signal S f This can eliminate the DC component in the current generated by the first photodetector 12262 and the second photodetector 12264, thus suppressing common-mode signals. Frequency discrimination signal S f It is transmitted to the first feedback circuit 1230.

[0125] Optical signal S f′1 and light signal S f′2 The equivalent optical signal after balanced detection can be represented by the following formula (5).

[0126] Optical signal S f′1 and light signal S f′2 The frequency discrimination signal after balanced detection can be represented by the following formula (6).

[0127] This electrical signal is only related to kt+δ. In the formula, R is the responsivity of the photodetector, and K is the gain coefficient of the photodetector.

[0128] First reference signal S r1 The linearity requirement can be an ideal signal output after linearly frequency-modulated light, meeting a preset linearity requirement, passes through a frequency discriminator circuit and a balanced detection circuit. The preset linearity requirement can be a frequency modulation nonlinearity on the order of one-thousandth, one-ten-thousandth, one-hundred-thousandth, one-millionth, or one-ten-millionth. Alternatively, the preset linearity requirement can be a frequency modulation nonlinearity not exceeding one-thousandth, one-ten-thousandth, one-hundred-thousandth, one-millionth, or one-ten-millionth. The preset linearity requirement can be set according to actual application needs. For example, if the detection range of a lidar is long (e.g., 300m–500m), the corresponding preset linearity requirement is higher. The preset linearity requirement can be set to a frequency modulation nonlinearity on the order of one-millionth, or a frequency modulation nonlinearity not exceeding one-millionth.

[0129] In some embodiments, the first reference signal S r1 It is a sine wave or a cosine wave. First reference signal S r1 It can be represented by the following formula (7).

[0130] For example, the first feedback circuit 1230 is based on the frequency discrimination signal. With the first reference signal Determine the first feedback signal S b1 The first feedback circuit 1230 will send the first feedback signal S b1 Output to laser 1210.

[0131] In some embodiments, based on the first feedback signal S b1 The current adjustment element can be set to adjust the driving current of the laser 1210, correct the nonlinear deviation of the frequency-modulated light, and make the frequency-modulated light reach the preset linearity requirements.

[0132] In some embodiments, the first reference signal S r1 It can be any type of wave, such as a triangular wave, sawtooth wave, trapezoidal wave, or straight line.

[0133] In some embodiments, the delay difference τ of the Mach-Zehnder interferometer can be on the order of millimeters, centimeters, decimeters, or meters. A larger delay difference τ in the Mach-Zehnder interferometer can improve the accuracy of the frequency discrimination signal. A smaller delay difference τ in the Mach-Zehnder interferometer can reduce the size of the Mach-Zehnder interferometer, which is beneficial for improving integration and chip-level integration. In this case, equation (6) can be rewritten as:

[0134] For example, the first reference signal can be represented by the following formula (9). r1 =v s (t)=K·2πτkt (9)

[0135] In some embodiments, the first feedback circuit 1230 may include a subtractor 1232 and a PID controller 1234.

[0136] Subtractor 1232 can be based on frequency discrimination signal S f and the first reference signal S r1 Determine the error signal S e =K·2πτδ. PID controller 1234 receives error signal S. e The PID controller 1234 can process the error signal S. e Process the signal and output the first feedback signal S. b1 To laser 1210.

[0137] For example, the subtractor 1232 can process the frequency discrimination signal S f and the first reference signal S r1 Subtraction is used to determine the frequency modulation nonlinearity error δ.

[0138] The first reference signal shown in equation (9) is a linear change. For example, the first reference signal shown in equation (9) corresponds to the frequency change of the frequency-modulated light. When the frequency change of the frequency-modulated light is a triangular wave, the first reference signal is also a triangular wave.

[0139] In some embodiments, continuing to refer to FIG12, a drive signal S can be applied to the phase modulator 1224. d Drive signal S d It can have the form shown in formula (9). In this case, the first reference signal S... r1 This is a fixed value. In this way, the structure of the first feedback circuit 1230 can be simplified.

[0140] Figure 13 shows an example diagram of a first feedback circuit of the present disclosure. Referring to Figure 13, in some embodiments, the first feedback circuit 1300 may include a multiplier 1302 and a filter 1304.

[0141] The first input of multiplier 1302 receives the frequency discrimination signal S. f The second input terminal receives the first reference signal S. r1 The multiplier 1302 can be based on the frequency discrimination signal S. f With the first reference signal S r1 Output phase detection signal

[0142] In some embodiments, the first reference signal Sr1 It can be generated by a sinusoidal oscillator.

[0143] Filter 1304 is coupled to multiplier 1302. Filter 1304 can receive phase detection signals. Output the first feedback signal S b1 .

[0144] In some embodiments, the first reference signal S r1 It can be expressed by the following formula (10). S r1 =s(t)=sin(2πτkt) (10)

[0145] Combining formulas (6) and (10), multiplier 1302 can be based on the frequency discrimination signal S. f and the first reference signal S r1 Output phase detection signal As shown in formula (11).

[0146] Low-pass filter 1304 receives phase detection signal Low-pass filter 1304 for phase detection signal Perform low-pass filtering and output the first feedback signal S. b1 As shown in formula (12).

[0147] The frequency modulation nonlinear deviation δ has a large bandwidth and varies at high frequencies. In comparison, It's just a low-frequency change. For example, the frequency of change of the frequency modulation nonlinear deviation δ is on the order of tens of MHz. The frequency of the change is on the order of Hz. By setting the low-pass filter 1304, the first feedback circuit 1300 can feed back low frequencies. Used to adjust the linearity of frequency-modulated light.

[0148] In some embodiments, the frequency-modulated light source provided in this disclosure includes a laser, a frequency discrimination circuit, a first feedback circuit, and a second feedback circuit. The laser can emit frequency-modulated light. The frequency discrimination circuit is coupled to the laser and can output a frequency discrimination signal. The input terminal of the first feedback circuit is coupled to the frequency discrimination circuit, and its output terminal is coupled to the laser. The first feedback circuit can output a first feedback signal based on the frequency discrimination signal and a first reference signal. The second feedback circuit is coupled to the frequency discrimination circuit, can receive the frequency discrimination signal and a second reference signal, and output a second feedback signal. The second feedback signal is used to adjust the operating point of the frequency discrimination circuit. The first feedback signal can correct the nonlinear deviation of the frequency-modulated light, so that the frequency-modulated light reaches a preset linearity requirement. The second feedback signal can adjust the operating point of the frequency discrimination circuit, correcting the nonlinear deviation present in the frequency-modulated light at the frequency corresponding to the operating point of the frequency discriminator. The operating point of the frequency discriminator can be consistent with the real-time frequency of the corrected frequency-modulated light, improving the accuracy of the frequency discrimination signal.

[0149] Figure 14 shows an example diagram of a frequency-modulated light source according to the present disclosure.

[0150] Referring to Figure 14, the frequency-modulated light source 1400 includes a laser 1410, a frequency discrimination circuit 1420, and a first feedback circuit 1430. The laser 1410 may be the same as or similar to lasers 301 and 1210. The frequency discrimination circuit 1420 may be the same as or similar to frequency discrimination circuit 1220. The first feedback circuit 1430 is based on the frequency discrimination signal S. f Determine the first feedback signal S b1 Used to correct the nonlinearity of the frequency-modulated light emitted by laser 1410.

[0151] On the other hand, this disclosure provides a method for modulating an optical signal. This method can be implemented by a frequency-modulated light source 1400. Exemplarily, the method for modulating an optical signal in some embodiments of this disclosure can be implemented by a first feedback circuit. The method includes:

[0152] A first signal is obtained by converting a first optical signal. Based on demodulation parameters, a first sub-signal and a second sub-signal are extracted from the first signal. Based on the first sub-signal and the second sub-signal, orthogonal demodulation processing is performed to obtain multiple demodulated signals to determine a first feedback signal. Based on the first feedback signal, the light is modulated.

[0153] Referring to Figure 14, exemplarily, the first optical signal can be the frequency-discriminating optical signal S. f′ The first signal can be the frequency discrimination signal S. fBased on the demodulation parameters, a first and a second component signal are extracted from the frequency-discriminating signal converted from the frequency-discriminating optical signal. Orthogonal demodulation is then performed on the first and second component signals to determine multiple demodulated signals. A first feedback signal is determined based on these multiple demodulated signals to correct the frequency modulation nonlinearity and modulate the light. Obtaining multiple demodulated signals through orthogonal demodulation to determine the first feedback signal results in higher accuracy and better linearity of the modulated light.

[0154] Referring to Figure 15, a schematic flowchart of some embodiments of the method for modulating optical signals of this disclosure is shown.

[0155] The method for modulating the optical signal includes:

[0156] Step S1510: Receive the frequency discrimination signal obtained by converting the frequency discrimination optical signal.

[0157] The frequency discrimination signal is an electrical signal, which is related to the photoelectric conversion result of the frequency discrimination optical signal. In step S1510, the electrical signal related to the photoelectric conversion result of the frequency discrimination optical signal is received.

[0158] Step S1520: Based on the demodulation parameters, extract the first sub-signal and the second sub-signal from the frequency discrimination signal.

[0159] Step S1530: Based on the first sub-signal and the second sub-signal, perform quadrature demodulation processing to determine multiple demodulated signals. Determine the first feedback signal based on the multiple demodulated signals.

[0160] Step S1540: Modulate the light based on the first feedback signal.

[0161] In some embodiments of this disclosure, the method for modulating the optical signal may further include: step S1503, performing photoelectric conversion on the frequency-discriminating optical signal to obtain a first electrical signal; step S1504, sampling the first electrical signal to obtain a frequency-discriminating signal.

[0162] In step S1503, the frequency-discriminating optical signal is photoelectrically converted to an electrical signal.

[0163] As shown in Figure 14, in some embodiments, in step S1503, the balanced detection circuit 1426 can perform photoelectric conversion on the frequency-discriminating optical signal and output a first electrical signal. The first electrical signal can characterize the light intensity of the frequency-discriminating optical signal.

[0164] In some embodiments, in step S1503, the frequency discrimination optical signal can be converted into a first electrical signal by balanced detection.

[0165] As an example, as shown in Figure 14, the balanced detection circuit 1426 includes a first photodetector 14262 and a second photodetector 14264. The anode of the first photodetector 14262 and the cathode of the second photodetector 14264 are connected.

[0166] In step S1504, the first electrical signal is sampled to digitize the analog electrical signal obtained from photoelectric conversion for subsequent digital processing. The frequency discrimination signal obtained in step S1504 is a digital signal.

[0167] In some embodiments, the frequency-modulated light source further includes an analog-to-digital converter (ADC, not shown in the figure). In step S1504, the ADC can sample the first electrical signal to obtain the frequency discrimination signal.

[0168] It should be noted that in some embodiments, the frequency discrimination circuit 1420 includes the analog-to-digital converter. The frequency discrimination circuit 1420 may include two analog-to-digital converters. The two analog-to-digital converters are respectively connected to the first photodetector 14262 and the second photodetector 14264.

[0169] Referring again to Figure 15, in some embodiments of this disclosure, the method for modulating the optical signal may further include: step S1501, receiving a second optical signal, the second optical signal including at least a portion of the initial optical signal or an initial modulated optical signal formed by modulating the initial optical signal. Step S1502, converting the second optical signal into a frequency-discriminating optical signal.

[0170] Steps S1501 and S1502 can convert the frequency information of the second optical signal into the light intensity information of the frequency-discriminating optical signal.

[0171] As shown in Figure 14, the second optical signal can be the detection light Out2. In some embodiments, in step S1501, the frequency discrimination circuit 1420 can receive the detection light Out2.

[0172] In some embodiments, the frequency-modulated light source 1400 includes a directly modulated laser. The directly modulated laser emits frequency-modulated light under the influence of a modulation signal. The detection light Out2 includes at least a portion of the initial light signal emitted by the directly modulated laser. In some embodiments, the frequency-modulated light source 1400 includes a laser and a modulator. The laser emits fixed-frequency light. The fixed-frequency light is modulated by the modulator to form frequency-modulated light. The detection light Out2 includes an initial modulated light signal formed by modulating the initial light signal.

[0173] For example, as shown in Figure 14, laser 1410 emits frequency-modulated light under the modulation of a modulation signal. The emitted frequency-modulated light is split into Out1 and Out2 by a coupler (not shown in the figure). Out1 serves as a probe light, which can be used to determine relevant information about objects in the probe space. Out2 serves as a detection light. In step S1501, coupler 14222 in frequency discrimination circuit 1420 receives the detection light Out2.

[0174] In some embodiments, in step S1502, the frequency discriminator can convert the frequency information of the detected light into the intensity information of the discriminant light signal. For example, the frequency discriminator may include at least one of a Mach-Zehnder interferometer, a fiber Bragg grating, a bandpass filter, and a microring.

[0175] As shown in Figure 14, in the frequency discriminator circuit 1420, the frequency discriminator 1422 includes couplers 14222 and 14224, and two waveguide arms 14226 and 14228. Waveguide arms 14226 and 14228 have an optical path difference. A phase modulator 1424 is disposed in the optical path of waveguide arm 14228 of the frequency discriminator 1422. The phase modulator 1424 can adjust the operating point of the frequency discriminator 1422, causing the operating point of the frequency discriminator 1422 to move with the center frequency of the laser 1410. A delay fiber is disposed in the optical path of waveguide arm 14226 of the frequency discriminator 1422, so that the two waveguides have a preset optical path difference.

[0176] Phase modulator 1424 introduces a phase modulation signal with frequency ω0 into waveguide arm 14228 of frequency discriminator 1422. Referring to Figure 14, phase modulator 1424 receives drive signal S. d ω0 can be the driving signal S d The angular frequency. After being transmitted by the frequency discriminator 1422, the frequency discriminant optical signal S f′ The light intensity can be expressed as:

[0177] In the formula, B is a constant, which is related to the beam splitting ratio of the coupler, the responsivity of the detector, and the circuit gain. C is the amplitude of the driving signal.

[0178] The expansion of the triangular Bessel is as follows:

[0179] Based on the Bessel expansion, the frequency-discriminating optical signal S f′ The light intensity, i.e. the light intensity shown in equation (13), can be obtained by performing a Bessel expansion:

[0180] In step S1510, the frequency discrimination signal is as shown in equation (16).

[0181] In some embodiments, the phase in equation (16) is generated by a phase-generated carrier (PGC). The demodulated signal is obtained. The PGC demodulation method has higher accuracy and better linearity, and can effectively improve the modulation effect of optical signals.

[0182] In step S1520, based on the demodulation parameters, the first sub-signal and the second sub-signal are extracted from the frequency discrimination signal and orthogonal demodulation is performed.

[0183] As shown in Figure 16, in some embodiments of this disclosure, the method for modulating an optical signal includes step S1620, extracting a first sub-signal and a second sub-signal from the frequency discrimination signal based on demodulation parameters. Step S1620 may be the same as or similar to step S1520. For example, step S1620 includes: step S1621, determining demodulation parameters based on a driving signal.

[0184] In some embodiments, the demodulation parameters include a first demodulation parameter and a second demodulation parameter with unequal angular frequencies. For example, the angular frequency of the second demodulation parameter may be twice the angular frequency of the first demodulation parameter. The angular frequency of the first demodulation parameter may be related to the drive signal S. d The angular frequencies are the same. For example, in step S1621, the first demodulation parameter can be expressed as cos(ω0t), and the second demodulation parameter can be expressed as cos(2ω0t).

[0185] In some embodiments of this disclosure, step S1620 further includes: step S1622, determining a first sub-signal based on the first demodulation parameters; and step S1623, determining a second sub-signal based on the second demodulation parameters. The first demodulation parameters and the second demodulation parameters are different.

[0186] For example, in step S1620, a sub-signal is extracted from the frequency discrimination signal by multiplying it with the demodulation parameters. In step S1622, a first sub-signal is determined based on the result of multiplying the frequency discrimination signal and the first demodulation parameters. In step S1623, a second sub-signal is determined based on the result of multiplying the frequency discrimination signal and the second demodulation parameters. Extracting sub-signals based on the demodulation parameters determined by the phase modulation signal allows for the extraction of components proportional to the high-frequency modulation frequency in the frequency discrimination signal, enabling quadrature demodulation.

[0187] In step S1622, the frequency discrimination signal shown in equation (4) is multiplied by the first demodulation parameter expressed as cos(ω0t), and the determined first sub-signal I1 is expressed as:

[0188] In step S1623, the frequency discrimination signal shown in equation (16) is multiplied by the second demodulation parameter expressed as cos(2ω0t), and the determined second sub-signal I2 is expressed as:

[0189] After extracting the first and second sub-signals, step S1530 is executed. Based on the first and second sub-signals, quadrature demodulation processing is performed to determine multiple demodulated signals. A first feedback signal is then determined based on these multiple demodulated signals.

[0190] In some embodiments of this disclosure, the method for modulating an optical signal includes step S1730, performing orthogonal demodulation processing based on the first sub-signal and the second sub-signal to determine a plurality of demodulated signals. A first feedback signal is then determined based on the plurality of demodulated signals. Step S1730 may be the same as or similar to step S1530.

[0191] For example, step S1730 includes: step S1731, removing the high-frequency components of the first sub-signal to obtain a first filtered signal. Step S1732, removing the high-frequency components of the second sub-signal to obtain a second filtered signal. Step S1733, determining the plurality of demodulated signals based on the phase information of the first and second filtered signals. Step S1734, determining a first feedback signal based on the plurality of demodulated signals.

[0192] Step S1731 removes high-frequency components from the sub-signal, retaining the baseband signal. For example, the first filtered signal obtained in step S1731 is the baseband signal from the first sub-signal. The second filtered signal obtained in step S1732 is the baseband signal from the second sub-signal.

[0193] In some embodiments, high-frequency components in the sub-signal can be removed by low-pass filtering. For example, step S1731 includes: performing low-pass filtering on the first sub-signal to obtain a first filtered signal. Step S1732 includes: performing low-pass filtering on the second sub-signal to obtain a second filtered signal.

[0194] In step S1731, the first filtered signal I1LP obtained after low-pass filtering of the first sub-signal I1 represented by equation (17) is expressed as:

[0195] In step S1732, the second filtered signal I2LP obtained after low-pass filtering of the second sub-signal I2 represented by equation (18) is expressed as:

[0196] The demodulated signal is determined based on the phase information of the filtered signal. Step S1733 includes: extracting the phase information of the filtered signal. For example, step S1733 includes: extracting the phase information of the first filtered signal and the phase information of the second filtered signal.

[0197] In some embodiments, the phase information of the filtered signal can be extracted through differentiation, which can more effectively extract the phase information during quadrature demodulation.

[0198] Step S1733 includes: obtaining phase information of the filtered signal through differentiation processing. The filtered signal is one of the first filtered signal and the second filtered signal. For example, step S1733 includes: obtaining phase information of the first filtered signal through differentiation processing; obtaining phase information of the second filtered signal through differentiation processing.

[0199] The derivative I1d of the first filtered signal I1LP, represented by equation (19), is expressed as:

[0200] The derivative I2d of the second filtered signal I2LP, expressed by equation (20), is as follows:

[0201] After extracting the phase information of the filtered signal, orthogonal demodulation is performed. For example, orthogonal demodulation can be achieved through cross-multiplication.

[0202] In some embodiments, in step S1833, the plurality of demodulated signals are determined based on the phase information of the first filtered signal and the second filtered signal. Step S1833 may be the same as or similar to step S1733 described above.

[0203] Step S1833 includes: Step S1833a, obtaining a first demodulated signal based on the phase information of the first filtered signal and the second filtered signal. Step S1833b, obtaining a second demodulated signal based on the phase information of the second filtered signal and the first filtered signal.

[0204] In step S1833a, the derivative I1d of the first filtered signal I1LP represented by equation (21) and the second filtered signal I2LP represented by equation (20) are multiplied together to determine the first demodulated signal as follows:

[0205] In step S1833b, the derivative I2d of the second filtered signal I2LP represented by equation (22) is multiplied by the first filtered signal I1LP represented by equation (19), and the determined second demodulated signal is expressed as:

[0206] In some embodiments of this disclosure, after obtaining the demodulated signal, common components in the demodulated signal are eliminated to further highlight the phase information. As shown in FIG19, in step S1934, a first feedback signal is determined based on the plurality of demodulated signals. Step S1934 may be the same as or similar to step S1734 described above.

[0207] In some embodiments, as shown in FIG6, step S1934 includes: step S1934a, eliminating the common component of the two demodulated signals; and step S1934b, generating the first feedback signal based on the result after eliminating the common component of the two demodulated optical signals.

[0208] For example, in step S1934a, the common component of the two demodulated signals can be eliminated by subtraction.

[0209] In some embodiments, in step S1934a, the two demodulated optical signals are subtracted to eliminate the common component between the two demodulated optical signals. For example, the first demodulated signal represented by equation (23) and the second demodulated signal represented by equation (24) are subtracted. This eliminates the common component of the demodulated signals and highlights the phase information.

[0210] For example, in step S1934b, the phase signal can be recovered by integration.

[0211] In some embodiments, in step S1934b, the result after eliminating the common component of the two demodulated optical signals is integrated to generate the first feedback signal.

[0212] In step S1934b, the first feedback signal generated by integrating the result of subtracting the first demodulated signal represented by equation (23) and the second demodulated signal represented by equation (24) is expressed as:

[0213] Phase information can be obtained from the integral result expressed by equation (25). This generates the first feedback signal.

[0214] It should be noted that in some embodiments, step S1934 further includes: step S1934c, performing noise reduction processing on the first feedback signal. By reducing the noise of the generated first feedback signal, the noise level of the first feedback signal S can be improved. b1 The signal-to-noise ratio is improved, thus enhancing the effect of optical modulation.

[0215] In some examples, in step S1934c, the low-frequency and DC components of the first feedback signal are removed, and the high-frequency components of the first feedback signal are retained to obtain the noise-reduced first feedback signal S. b1In some embodiments, in step S1934c, the first feedback signal is high-pass filtered to achieve noise reduction.

[0216] In step S1540, based on the first feedback signal S b1 Modulate the light.

[0217] For example, the modulation is frequency modulation. For instance, the modulation is linear frequency modulation. In step S1540, based on the determined first feedback signal S... b1 The light is modulated to correct the frequency modulation nonlinearity.

[0218] For example, referring to Figure 14, in step S1540, the first feedback signal S is determined. b1 Then, the first feedback signal S b1 It is provided to the laser 110 to achieve modulation of light.

[0219] The frequency-modulated light source 1400 may include a driving circuit (not shown). The driving circuit can provide a driving current to the laser 1410. The amplitude of the driving current can vary over time, causing the laser 1410 to emit frequency-modulated light. For example, the frequency-modulated light includes linearly frequency-modulated light. Exemplarily, the first feedback circuit 1430 outputs a first feedback signal S. b1 Output to the drive circuit. Based on the first feedback signal S b1 Adjusting the drive current can correct the nonlinear deviation of frequency-modulated light and improve linearity.

[0220] In some embodiments, as shown in FIG19, step S1934 further includes: step S1934c, performing noise reduction processing on the first feedback signal. As shown in FIG2, in step S1540, based on the noise-reduced first feedback signal S b1 Modulate the light.

[0221] Phase information can be obtained according to some embodiments of this disclosure. It can be obtained

[0222] Integrating, we can obtain φn. This leads to the first feedback signal S. b1 First feedback signal S b1 This can characterize the phase noise introduced by the frequency modulation nonlinearity of the modulated light. The first feedback circuit 1430 converts the first feedback signal S... b1 Feedback is sent to laser 1410 based on the first feedback signal S b1 The frequency modulation signal of the laser is corrected. Using the corrected frequency modulation signal to perform linear frequency modulation on the laser can improve the frequency modulation linearity of the optical signal.

[0223] In some embodiments, the frequency-modulated light source 1400 may further include a driving circuit (not shown). The driving circuit can provide a driving current to the laser 1410. The output frequency of the laser is related to the driving current. The driving circuit can generate a driving current whose amplitude varies with time, thereby changing the output frequency of the laser to achieve frequency modulation. Exemplarily, the output frequency of the laser changes linearly with time, and the change pattern can be in the form of a sawtooth wave, a triangular wave, a trapezoidal wave, etc.

[0224] For example, the first feedback circuit 1430 will send the first feedback signal S b1 Output to the drive circuit. Based on the first feedback signal S b1 Adjusting the drive current can correct the nonlinear deviation of frequency-modulated light and improve linearity.

[0225] Accordingly, this disclosure also provides a frequency-modulated light source.

[0226] As shown in Figure 14, the frequency-modulated light source includes: a laser 1410, a frequency discrimination circuit 1420, a feedback circuit 1430, and a frequency modulation circuit (not shown in the figure). The laser 1410 generates an initial optical signal. The frequency discrimination circuit 1420 is configured to receive a second optical signal and convert the frequency information of the second optical signal into the intensity information of the frequency-discriminated optical signal, wherein the second optical signal includes at least a portion of the initial optical signal or an initial modulated optical signal formed by modulating the initial optical signal. The feedback circuit 1430 receives the frequency-discriminated signal obtained from the frequency-discriminated optical signal. The feedback circuit is further configured to extract a first sub-signal and a second sub-signal from the frequency-discriminated signal based on the demodulated signal. The feedback circuit is also configured to perform quadrature demodulation processing based on the first sub-signal and the second sub-signal to obtain multiple demodulated signals to determine a first feedback signal. The frequency modulation circuit is configured to modulate the light based on the first feedback signal.

[0227] The laser 1410 can output laser light. In some embodiments of this disclosure, the laser 1410 may include a distributed feedback laser (DFB).

[0228] In some embodiments of this disclosure, the laser can be modulated by an electric current. The initial light generated by the laser can be frequency-modulated light. In some embodiments of this disclosure, the initial light generated by the laser can be fixed-frequency light. The frequency-modulated light source may further include a modulator. The modulator modulates the fixed-frequency light to obtain frequency-modulated light.

[0229] For example, the driving circuit is connected to the laser 1410. The driving circuit provides a driving signal to the laser 1410, changing the current of the laser 1410 to change the frequency of the light output by the laser 1410, thereby achieving frequency modulation.

[0230] The frequency discrimination circuit 1420 can receive the second optical signal and convert the frequency information of the second optical signal into the light intensity information of the frequency discrimination optical signal.

[0231] In some embodiments of the present invention, the frequency discrimination circuit includes a frequency discriminator 1422. The frequency discriminator 1422 is configured to convert the second optical signal into a frequency-discriminated optical signal, and to convert the frequency information of the second optical signal into the light intensity information of the frequency-discriminated optical signal. For example, the frequency discriminator may include at least one of a Mach-Zehnder interferometer, a fiber Bragg grating, a bandpass filter, and a microring.

[0232] As shown in Figure 14, in the frequency discriminator circuit 1420, the frequency discriminator 1422 includes coupler 14222, coupler 14224, waveguide arm 14226, and waveguide arm 14228. Waveguide arm 14228 is equipped with a phase modulator 1424. The phase modulator 1424 operates under the drive signal S. d The operating point of the frequency discriminator is adjusted under the control of the laser 1410. The operating point of the frequency discriminator moves with the center frequency of the laser 1410. A delay timer is provided on the waveguide arm 14226. Waveguide arms 14226 and 14228 have a preset optical path difference.

[0233] For example, the drive signal S d The angular frequency of the laser is the same as the angular frequency of the laser's driving current, which allows the operating point of the frequency discriminator 1422 to move with the center frequency of the laser 1410.

[0234] In some embodiments of the present invention, the frequency discrimination circuit 1420 may further perform photoelectric conversion on the frequency discrimination optical signal to obtain a frequency discrimination signal. The first photodetector 14262 and the second photodetector 14264 in the frequency discrimination circuit 1420 perform balanced detection on the frequency discrimination optical signal and output a first electrical signal.

[0235] The frequency discrimination circuit 1420 can also sample the first electrical signal and output a frequency discrimination signal S. f The frequency discrimination circuit 1420 includes an ADC (not shown in the figure). The ADC can sample the first electrical signal and output a frequency discrimination signal S. f .

[0236] In some embodiments, the first feedback circuit 1430 includes an ADC (not shown). The ADC can sample the first electrical signal output by the balanced detection circuit 1426 and output a frequency discrimination signal S. f .

[0237] The first feedback circuit 1430 can be based on the frequency discrimination signal S f Determine the first feedback signal S b1 The driving circuit modulates the light according to the first feedback signal.

[0238] It should be noted that in some embodiments, the driving circuit can be directly integrated into the laser. In other embodiments, the frequency-modulated light source can also have a separate driving circuit.

[0239] Figure 20 shows an example diagram of a frequency-modulated light source according to the present disclosure. Referring to Figure 20, in some embodiments, the frequency-modulated light source 2000 includes a laser 2002, a frequency discrimination circuit 2004, a first feedback circuit 2006, and a second feedback circuit 2008.

[0240] Laser 2002 can emit frequency-modulated light. Laser 2002 can be the same as or similar to laser 302, laser 1210, and laser 1410. The frequency-modulated light emitted by laser 2002 is divided into two parts. Out1 is used as probe light. Out2 is used as detection light and is transmitted to frequency discriminator circuit 2004.

[0241] The frequency discriminator circuit 2004 is coupled to the laser 2002. The frequency discriminator circuit 2004 can output a frequency discriminator signal S. f Frequency discriminator circuit 2004 may be the same as or similar to frequency discriminator circuit 304, frequency discriminator circuit 1220, or frequency discriminator circuit 1420.

[0242] Referring again to Figure 20, the input of the first feedback circuit 2006 is coupled to the frequency discriminator circuit 2004, and its output is coupled to the laser 2002. The first feedback circuit 2006 can be based on the frequency discriminator signal S. f With the first reference signal S r1 Output the first feedback signal S b1 First feedback signal S b1 It can be used to correct the nonlinear deviation of frequency-modulated light and improve the linearity of frequency-modulated light.

[0243] The first feedback circuit 2006 may be the same as or similar to the first feedback circuit 306, the first feedback circuit 1230, or the first feedback circuit 1430.

[0244] The second feedback circuit 2008 is coupled to the frequency discrimination circuit 2004. The second feedback circuit 2008 can receive the frequency discrimination signal S. f With the second reference signal S r2 Output the second feedback signal S b2 Frequency discriminator circuit 2004. Second feedback signal S b2 It can be used to adjust the operating point of the frequency discriminator circuit 2004.

[0245] Second feedback signal S b2 The operating point of the frequency discriminator can be adjusted accordingly based on the nonlinear deviation of the frequency-modulated light. The frequency corresponding to the operating point of the frequency discriminator is consistent with the real-time frequency of the frequency-modulated light emitted by the laser, which can improve the accuracy of the frequency discrimination signal.

[0246] In some embodiments, the second feedback circuit may include a digital signal processing circuit.

[0247] For example, a digital signal processing circuit can perform a Hilbert transform on the frequency discrimination signal to determine the second feedback signal.

[0248] For example, a digital signal processing circuit can perform sinusoidal signal fitting on the frequency discrimination signal to determine the second feedback signal.

[0249] In some embodiments, the second feedback circuit may include an analog signal processing circuit.

[0250] Figure 21 shows an example diagram of a frequency-modulated light source according to the present disclosure. Referring to Figure 21, the frequency-modulated light source 2100 includes a laser 2110, a frequency discrimination circuit 2120, a first feedback circuit 2130, and a second feedback circuit 2140.

[0251] Laser 2110 may be the same as or similar to laser 302, laser 1210, laser 1410, or laser 2002. The frequency-modulated light emitted by laser 2110 is split into two parts. Out1 serves as the probe light. Out2 serves as the detection light and is transmitted to the frequency discriminator circuit 2120.

[0252] The frequency discrimination circuit 2120 is coupled to the laser 2110. The frequency discrimination circuit 2120 can output a frequency discrimination signal S. f Frequency discrimination circuit 2120 may be the same as or similar to frequency discrimination circuit 304, frequency discrimination circuit 1220, frequency discrimination circuit 1420, or frequency discrimination circuit 2004.

[0253] Referring to Figure 21, the frequency discrimination circuit 2120 includes a Mach-Zehnder interferometer 2122 and a balanced detection circuit 2126. The Mach-Zehnder interferometer 2122 receives the detection light Out2 and outputs the frequency discrimination light signal S. f′ The Mach-Zehnder interferometer 2122 can be the same as or similar to the Mach-Zehnder interferometer 600, Mach-Zehnder interferometer 910, Mach-Zehnder interferometer 1222, or Mach-Zehnder interferometer 1422. The balanced detection circuit 2126 receives the frequency-discriminating optical signal S. f′ Output frequency discrimination signal S f The balance detection circuit 2126 may be the same as or similar to the balance detection circuit 1100, balance detection circuit 1226, or balance detection circuit 1426.

[0254] In some embodiments, the first feedback circuit 2130 may include a subtractor 2132 and a PID controller 2134. First reference signal S r1 It can have the form shown in equation (9). The subtractor 2132 can be based on the frequency discrimination signal S. f and the first reference signal S r1 Determine the error signal S e =K·2πτδ. The PID controller 2134 receives the error signal S. e The PID controller 2134 can process the error signal S. e Process the signal and output the first feedback signal S. b1 To laser 2110.

[0255] In some embodiments, the second feedback circuit 2140 includes a subtractor 2142 and a PID controller 2144. The second reference signal S r2 It can also have the form shown in equation (9). The subtractor 2142 can be based on the frequency discrimination signal S. f Second reference signal S r2 Determine the error signal S e =K·2πτδ. The PID controller 2144 receives the error signal S. e The PID controller 2144 can process the error signal S. e Process the signal and output the second feedback signal S. b2 To phase modulator 2124.

[0256] In some embodiments, the frequency-modulated light source 2100 further includes an adder 2145. The adder 2145 receives a second feedback signal S. b2 and drive signal S d Adder 2145 will input the second feedback signal S b2 and drive signal S d The superimposed signal is output to the phase modulator 2124 to control the operating point of the phase modulator 2124. For example, the drive signal S... d It has the form shown in equation (9). At this time, the first reference signal S... r1 This is a constant value. The first reference signal S can be reduced. r1 The storage space occupied simplifies the structure of the first feedback circuit 2130.

[0257] In some embodiments, the first feedback circuit 2130 includes a multiplier 2132 and a PID controller 2134. First reference signal S r1 It can have the form shown in equation (10). The multiplier 2132 can be based on the frequency discrimination signal S. f and the first reference signal S r1 Output phase detection signal Low-pass filter 2134 receives phase detection signal Low-pass filter 2134 for phase detection signal Perform low-pass filtering and output the first feedback signal S. b1 .

[0258] In some embodiments, the second feedback circuit 2140 may include a multiplier 2142 and a low-pass filter 2144. Exemplarily, the second reference signal S... r2 It can have the form shown in equation (10). The multiplier 2142 can be based on the frequency discrimination signal S. f Second reference signal S r2 Output phase detection signal Low-pass filter 2144 receives phase detection signal Low-pass filter 2144 pairs phase detection signals Perform low-pass filtering and output the second feedback signal S. b2 .

[0259] Based on the second feedback signal S b2 The feedback phase change can eliminate the nonlinear deviation of the frequency-modulated light at the frequency corresponding to the operating point of the frequency discriminator. The frequency corresponding to the operating point of the frequency discriminator is consistent with the real-time frequency of the frequency-modulated light emitted by the laser.

[0260] It should be noted that in some embodiments of this disclosure, the structures of the first feedback circuit and the second feedback circuit may be the same or similar. For example, the first feedback circuit and the second feedback circuit may include a subtractor and a PID controller. As another example, the first feedback circuit and the second feedback circuit may include a multiplier and a low-pass filter. In some embodiments, the structures of the first feedback circuit and the second feedback circuit may also be different. For example, the first feedback circuit may include a subtractor and a PID controller, while the second feedback circuit may include a multiplier and a low-pass filter.

[0261] This disclosure also provides a lidar. The lidar includes the frequency-modulated light source described in any of the foregoing embodiments.

[0262] In some embodiments, the lidar includes a frequency-modulated light source, a receiving component, and a processor. The frequency-modulated light source can be a frequency-modulated light source as described in the foregoing embodiments of this disclosure. The frequency-modulated light source may include a frequency-modulated laser. The frequency-modulated laser can generate a local oscillator light and a probe light. The probe light is emitted outside the lidar. The probe light is reflected by an object to form an echo light. The receiving component receives the echo light. The receiving component can also beat the local oscillator light and the echo light to obtain beat-frequency light. The receiving component may, for example, include a detector. The detector can convert the beat-frequency light into an electrical signal. The processor can determine one or more pieces of information, such as the distance and velocity of the object, based on the electrical signal obtained from the beat-frequency light conversion.

[0263] The lidar using some embodiments of this disclosure emits linearly frequency-modulated light that meets preset linearity requirements through a frequency-modulated light source, which can obtain accurate detection results and improve the detection accuracy and reliability of the lidar.

[0264] Furthermore, the present invention also provides an FMCW lidar, comprising: a frequency-modulated light source, a receiving component, and a processor. The frequency-modulated light source is the frequency-modulated light source of the present invention. The frequency-modulated light source can generate local oscillator light and probe light. The probe light is emitted outside the lidar. The probe light is reflected to form echo light. The receiving component is configured to receive the echo light. The processor is configured to determine one or more pieces of information, including the distance and velocity of the object, based on the local oscillator light and the echo light.

[0265] The frequency-modulated light source generates linearly frequency-modulated light. Local oscillator light, detection light, and probe light can be separated from the linearly frequency-modulated light. The probe light is emitted to the outside of the lidar. The probe light signal is reflected by an object, and the reflected light returns to the lidar, forming an echo light. The receiving component receives the echo light. The echo light and the local oscillator light are coupled coherently to form coherent light for object detection. The frequency-modulated light source is the frequency-modulated light source of this invention. The first feedback circuit, based on the first feedback signal determined by the detection light, can be used to correct the nonlinear deviation of the frequency-modulated light. The light output by the frequency-modulated light source has high linearity. The FMCW lidar can achieve higher precision, faster speed, and longer-range laser detection.

[0266] Processors can be implemented as application-specific integrated circuits (ASICs), or as hardware circuits implemented with programmable logic devices (PLDs), such as field-programmable gate arrays (FPGAs), microcontroller units (MCUs), or digital signal processors (DSPs), which provide high processing efficiency. In other implementations, a central processing unit (CPU) can also be selected.

[0267] In this disclosure, unless otherwise expressly specified and limited, ordinal numbers, such as "first," "second," etc., are used only to distinguish and describe related objects, and should not be construed as indicating or implying the relative importance or order between related objects. Furthermore, ordinal numbers do not represent the quantity of related objects.

[0268] The terms "or" and "and / or" in this disclosure are used to describe relationships between related objects, indicating a non-exclusive inclusion. For example, "A and / or B" and "A or B" can both include: "A alone," "B alone," or "A and B," where "A" and "B" can include a single object or multiple objects. Similarly, "A, B and / or C," "A, B or C," and "A, B and C" can both include: "A alone," "B alone," "C alone," "A and B," "A and C," "B and C," or "A, B and C," where "A," "B," and "C" can include a single object or multiple objects. Additionally, the " / " in this disclosure is used to indicate an "or" relationship between related objects. The meanings of "at least one of A or B" and "one or more of A and B" in this disclosure are the same as the meaning of "A or B" above. The meanings of "one or more of A, B, and C" and "at least one of A, B, or C" are the same as the meaning of "A, B, or C" above. The meaning of "one or more of A, B, and C" is the same as the meaning of "A, B, or C" above.

[0269] In the above embodiments, the descriptions of each embodiment have their own emphasis. Parts not described in detail or recorded in a certain embodiment can be referred to in the relevant descriptions of other embodiments. Furthermore, the above embodiments can be freely combined as needed. Although the embodiments of this disclosure have been disclosed above, this disclosure is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of this disclosure.

Claims

1. A frequency-modulated light source, comprising: The laser is configured to emit frequency-modulated light. A frequency discrimination circuit, coupled to the laser, is configured to output a frequency discrimination signal, and The first feedback circuit, with its input terminal coupled to the frequency discrimination circuit and its output terminal coupled to the laser, is configured to output a first feedback signal based on the frequency discrimination signal and the first reference signal, so as to adjust the linearity of the frequency-modulated light.

2. The circuit of claim 1, wherein, The first feedback circuit includes: The subtractor is configured to output an error signal based on the frequency discrimination signal and the first reference signal. A PID controller, coupled to the subtractor, is configured to receive the error signal and output the first feedback signal.

3. The circuit according to claim 1, characterized in that, The frequency discrimination circuit includes: Frequency discriminator, and A phase modulation circuit, coupled to the frequency discriminator, is configured to adjust the operating point of the frequency discriminator based on a second feedback signal.

4. The circuit according to claim 3, characterized in that, Also includes: The second feedback circuit, coupled to the frequency discrimination circuit, is configured to receive the frequency discrimination signal and the second reference signal, and output a second feedback signal to the phase modulation circuit to adjust the operating point of the frequency discrimination circuit.

5. The circuit according to claim 4, characterized in that, The second feedback circuit includes at least one of the following: Analog signal processing circuits, or Digital signal processing circuit.

6. The circuit according to claim 5, characterized in that, The analog signal processing circuit includes: The multiplier is configured to output a phase detection signal based on the frequency discrimination signal and the second reference signal, and A filter, coupled to the multiplier, is configured to receive the phase detection signal and output the second feedback signal.

7. The circuit according to claim 5, characterized in that, The digital signal processing circuit is configured to perform at least one of Hilbert transform and sine signal fitting on the frequency discrimination signal to determine the second feedback signal.

8. The circuit according to claim 3, characterized in that, The frequency discriminator includes at least one of the following: Mach-Zehnder interferometer Fiber Bragg grating Bandpass filter, Fabry-Perot resonator, or Microrings.

9. The circuit according to claim 3, characterized in that, The phase modulation circuit includes at least one of the following: Phase modulator, Semiconductor optical amplifier, piezoelectric ceramics Thermally adjustable phase shifter, or Electrically adjustable phase shifter.

10. The circuit according to claim 3, characterized in that, The frequency discrimination circuit also includes: A balanced detection circuit, wherein the input terminal of the balanced detection circuit is coupled to the frequency discriminator, and the output terminal of the balanced detection circuit is coupled to the first feedback circuit and the second feedback circuit.

11. The circuit according to claim 10, characterized in that, The balance detection circuit includes: A first photodetector and a second photodetector, wherein the anode of the first photodetector is coupled to the cathode of the second photodetector, and the first photodetector and the second photodetector are configured to convert optical signals into electrical signals.

12. A lidar, comprising: Frequency-modulated light sources, including: A laser configured to emit frequency-modulated light, which can be divided into probe light and detection light. A frequency discrimination circuit, coupled to the laser, is configured to receive the detection light and output a frequency discrimination signal. The first feedback circuit, with its input terminal coupled to the frequency discrimination circuit and its output terminal coupled to the laser, is configured to output a first feedback signal based on the frequency discrimination signal and the first reference signal, so as to adjust the linearity of the frequency-modulated light. A receiving component is configured to receive the echo light reflected by the probe light from an object. The receiving component is further configured to receive a local oscillator light separated from the frequency-modulated light or the probe light, beat the local oscillator light with the echo light to obtain beat-frequency light, and the receiving component is further configured to photoelectrically convert the beat-frequency light and output an electrical signal. The processor is configured to determine one or more pieces of information, including distance and velocity, of the object based on the electrical signal.

Images