Signal processing apparatus, detection apparatus, and terminal device

Abstract

A signal processing apparatus, a detection apparatus, and a terminal device, relating to the technical field of detection, and used for reducing the cost of optical delay lines and the space occupied by the optical delay lines. The signal processing apparatus comprises a first frequency modulation photoelectric loop (110) and a second frequency modulation photoelectric loop (210). The first frequency modulation photoelectric loop (110) and the second frequency modulation photoelectric loop (210) share a mode conversion element (300) and an optical delay line (400). The mode conversion element (300) outputs a first optical signal (S11) in the first frequency modulation photoelectric loop (110) and a second optical signal (S21) in the second frequency modulation photoelectric loop (210) to the optical delay line (400) in different modes, outputs a delayed first optical signal (S11') to a frequency mixer (114) in the first frequency modulation photoelectric loop (110), and outputs a delayed second optical signal (S21') to a frequency mixer (214) in the second frequency modulation photoelectric loop (210). The signal processing apparatus can achieve the effect that a plurality of frequency modulation photoelectric circuits (110, 210) share the same optical delay line (400) by means of mode multiplexing, thereby reducing the number of optical delay lines (400) needing to be provided in the signal processing apparatus, and reducing the volume of the optical delay lines (400) and the space occupied by the optical delay lines (400).

Description

A signal processing device, a detection device, and a terminal equipment Technical Field

[0001] This application relates to the field of detection technology, and in particular to a signal processing device, a detection device, and a terminal device. Background Technology

[0002] Frequency-modulated continuous wave (FMCW) lidar (light detection and ranging) is currently a mainstream type of LiDAR. It detects distance and velocity by directly changing the frequency of the laser's emission source. As shown in Figure 1a, ideally, the frequency of the modulation signal (L1) input to the laser in an FMCW LiDAR is linearly related to time. This linear relationship is reflected linearly in the frequency of the laser's emitted beam, making the frequency change (L2) of the laser's emitted beam also linearly related to time.

[0003] However, during frequency modulation, the internal physical mechanisms of the laser (such as imperfections in manufacturing processes and thermal effects) may cause a nonlinear relationship between the modulation signal L1 input to the laser and the frequency of the laser beam emitted from the laser. This, in turn, leads to a nonlinear change in the frequency of the laser beam emitted over time, L2, resulting in a frequency modulation nonlinearity phenomenon, as shown in Figure 1b. This nonlinearity affects the measurement accuracy of the FMCW LiDAR. To address this issue, the modulation signal L1 input to the laser needs to be calibrated. However, current mainstream calibration schemes typically use an asymmetric Mach-Zehnder interferometer (AMZI) structure based on optical delay lines. This structure requires a large number of optical delay lines, especially in scenarios with a large number of lasers, where the number of optical delay lines increases exponentially. Such a large number of optical delay lines occupies a significant amount of space in the FMCW LiDAR and also results in high hardware costs.

[0004] In summary, reducing the cost and space occupied by optical delay lines is a pressing technical problem that needs to be solved in the field of FMCW LiDAR. Summary of the Invention

[0005] This application provides a signal processing device, a detection device, and a terminal device to reduce the cost and space occupied by optical delay lines.

[0006] In a first aspect, this application provides a signal processing apparatus, including a first frequency-modulated (FM) optoelectronic circuit and a second FM optoelectronic circuit. Each FM optoelectronic circuit includes a light source, a beam splitter, a mode conversion element, an optical delay line, and a mixer. The first and second FM optoelectronic circuits share the mode conversion element and the optical delay line, which supports optical signal transmission in at least two modes. The mode conversion element receives a first optical signal split by the beam splitter in the first FM optoelectronic circuit and a second optical signal split by the beam splitter in the second FM optoelectronic circuit. It outputs the first and second optical signals in different modes to the optical delay line, outputs the delayed first optical signal in the original mode of the first FM optoelectronic circuit to the mixer in the first FM optoelectronic circuit, and outputs the delayed second optical signal in the original mode of the second FM optoelectronic circuit to the mixer in the second FM optoelectronic circuit.

[0007] Based on the above signal processing device structure, by designing the optical delay line to support multimode transmission, mode multiplexing can be used to achieve the effect of multiple frequency-modulated optoelectronic circuits sharing the same optical delay line. This reduces the number of optical delay lines required in the signal processing device, lowers their size and space occupation, and saves on hardware costs. Therefore, when this signal processing device is applied to detection devices, such as FMCW LiDAR, the length of the optical delay lines required in the FMCW LiDAR can be reduced, simplifying the FMCW LiDAR system architecture and lowering its system cost.

[0008] Optionally, the structure of the mode conversion element can be varied, including but not limited to the following structure one and structure two.

[0009] Structure 1: The mode conversion element includes a first mode converter and a second mode converter. The first mode converter is connected between the beam splitter of the first frequency-modulated optoelectronic circuit and the first end of the optical delay line. The second mode converter is connected between the mixer of the first frequency-modulated optoelectronic circuit and the second end of the optical delay line. The first mode converter is used to convert the first optical signal into the fundamental mode signal in the optical delay line and output it to the optical delay line. The second mode converter is used to convert the fundamental mode signal after delay processing by the optical delay line into the first optical signal after delay processing in the first frequency-modulated optoelectronic circuit and output it to the mixer in the first frequency-modulated optoelectronic circuit.

[0010] Based on the above structure, the splitting element and mixer in the first frequency modulation optoelectronic circuit can be directly connected to both ends of the multimode optical delay line through the first mode converter and the second mode converter. In this way, the optical signal in the first frequency modulation optoelectronic circuit can be transmitted as the fundamental mode signal in the multimode optical delay line. The mode spot size required for the fundamental mode signal is small, and the size at both ends of the multimode optical delay line is sufficient to receive the fundamental mode signal.

[0011] In one example of structure one, the mode conversion element further includes a third mode converter and a fourth mode converter. One end of the third mode converter is connected to the beam splitter of the second frequency-modulated optoelectronic circuit, and the other end is coupled to a first position of the optical delay line, which is located between the first mode converter and the first end of the optical delay line. One end of the fourth mode converter is connected to the mixer of the second frequency-modulated optoelectronic circuit, and the other end is coupled to a second position of the optical delay line, which is located between the second mode converter and the second end of the optical delay line. The third mode converter is used to convert the second optical signal into a higher-order mode signal in the optical delay line and couple it into the optical delay line at the first position. The fourth mode converter is used to convert the higher-order mode signal after delay processing by the optical delay line into the second optical signal after delay processing in the second frequency-modulated optoelectronic circuit and couple it out to the mixer in the second frequency-modulated optoelectronic circuit at the second position.

[0012] Based on the above example, the splitter and mixer in the second frequency modulation optoelectronic circuit can be coupled to two positions on the multimode optical delay line in a non-contact manner using a third mode converter and a fourth mode converter. This allows the optical signal in the second frequency modulation optoelectronic circuit to be smoothly coupled to the optical delay line while maintaining the same transmission direction as the optical signal in the first frequency modulation optoelectronic circuit, so that the optical signals in the two frequency modulation optoelectronic circuits can be transmitted in the same direction using the same optical delay line.

[0013] In another example of structure one, the mode conversion element further includes a third mode converter and a fourth mode converter. One end of the third mode converter is connected to the beam splitter of the second frequency-modulated optoelectronic circuit, and the other end is coupled to a second position of the optical delay line, which is located between the second mode converter and the second end of the optical delay line. One end of the fourth mode converter is connected to the mixer of the second frequency-modulated optoelectronic circuit, and the other end is coupled to a first position of the optical delay line, which is located between the first mode converter and the first end of the optical delay line. The third mode converter is used to convert the second optical signal into a higher-order mode signal in the optical delay line and couple it into the optical delay line at the second position. The fourth mode converter is used to convert the higher-order mode signal after delay processing by the optical delay line into the second optical signal after delay processing in the second frequency-modulated optoelectronic circuit and couple it out to the mixer in the second frequency-modulated optoelectronic circuit at the first position.

[0014] Based on the above example, the optical signal in the second frequency-modulated optoelectronic circuit can be smoothly coupled to the optical delay line through the third mode converter and the fourth mode converter, while maintaining the opposite transmission direction to the optical signal in the first frequency-modulated optoelectronic circuit, so as to use the same optical delay line to transmit the optical signals in the two frequency-modulated optoelectronic circuits in reverse.

[0015] Structure 2, the mode conversion element includes a first optical transmission element, a first mode converter, and a reflective element. The first optical transmission element is connected between the beam splitter of the first frequency-modulated optoelectronic circuit, the mixer in the first frequency-modulated optoelectronic circuit, and the first end of the first mode converter. The second end of the first mode converter is connected to the first end of the optical delay line. The first optical transmission element is used to transmit the first optical signal from the beam splitter in the first frequency-modulated optoelectronic circuit to the first mode converter, and to transmit the delayed signal from the first mode converter to the mixer in the first frequency-modulated optoelectronic circuit. The first mode converter is used to convert the first optical signal from the first optical transmission element into a fundamental mode signal in the optical delay line and output it to the optical delay line, and to convert the fundamental mode signal after two delays in the optical delay line into a delayed signal in the first frequency-modulated optoelectronic circuit and output it to the first optical transmission element. The reflective element is used to reflect the fundamental mode signal after the first delay in the optical delay line back to the optical delay line.

[0016] Based on the above structure two, by setting optical transmission and reflection elements, the signal to be delayed can pass through the same optical delay line twice, thus reusing the same optical delay line to achieve two delays for the signal. Compared with existing technologies, the physical length of the optical delay line can be further reduced by 1 / 2 without reducing the delay time of the signal to be delayed. It is possible to maintain the original delay effect while further reducing the size and cost of the optical delay line.

[0017] In one example of structure two, the reflective element includes a second mode converter and a first reflector. The second mode converter is connected between the second end of the optical delay line and the first reflector. It is used to convert the fundamental mode signal after the initial delay of the optical delay line into the initial delayed signal in the first frequency-modulated photoelectric circuit and output it to the first reflector, and to convert the initial delayed signal reflected back by the first reflector into the fundamental mode signal in the optical delay line and output it to the optical delay line.

[0018] Based on the above example, a unique reflector can be set for the first frequency modulation photoelectric circuit so that the optical signal of the first frequency modulation photoelectric circuit can enter the corresponding reflector for independent reflection, and then be entered into the multimode optical delay line together by the second mode converter in the form of mode multiplexing for secondary delay. This method can avoid the interference caused by reflecting multiple signals at the same time, and improve the signal quality reflected back to the multimode optical delay line while reducing the signal reflection loss.

[0019] In one example of Structure 2, the mode conversion element further includes a second optical transmission element and a third mode converter. The second optical transmission element is connected between the beam splitter of the second frequency-modulated optoelectronic circuit, the mixer in the second frequency-modulated optoelectronic circuit, and the first end of the third mode converter. The second end of the third mode converter is coupled to a first position of the optical delay line, which is located between the first mode converter and the first end of the optical delay line. The second optical transmission element is used to transmit the second optical signal from the beam splitter in the second frequency-modulated optoelectronic circuit to the third mode converter. The third mode converter is used to convert the second optical signal from the second optical transmission element into a higher-order mode signal in the optical delay line and couple it into the optical delay line at the first position. The reflection element is used to reflect the higher-order mode signal after the initial delay of the optical delay line back to the optical delay line. The third mode converter is also used to convert the higher-order mode signal after two delays of the optical delay line into a delayed signal in the second frequency-modulated optoelectronic circuit and couple it out to the second optical transmission element at the first position. The second optical transmission element is also used to transmit the delayed signal from the third mode converter to the mixer in the second frequency-modulated optoelectronic circuit.

[0020] Based on the above example, by setting a second optical transmission element, a third mode converter, and a reflection element, the optical signal in the second frequency modulation optoelectronic circuit can be smoothly coupled into the optical delay line, and the optical signal after the second delay can be smoothly coupled out of the optical delay line, while maintaining the same transmission direction as the optical signal in the first frequency modulation optoelectronic circuit, so as to use the same optical delay line to transmit the optical signals in the two frequency modulation optoelectronic circuits back and forth in the same direction.

[0021] In a further example, the reflective element includes a fourth mode converter and a second reflector. One end of the fourth mode converter is connected to the second reflector, and the other end is coupled to a second position of the optical delay line. The second position is located between the second mode converter and the second end of the optical delay line. The fourth mode converter is used to convert the high-order mode signal after the initial delay of the optical delay line into the initial delayed signal in the second frequency-modulated optoelectronic circuit and couple it out to the second reflector at the second position. It is also used to convert the initial delayed signal reflected back by the second reflector into a high-order mode signal in the optical delay line and couple it out to the optical delay line at the second position.

[0022] Based on the above example, a unique reflector can be set for the second frequency modulation photoelectric circuit so that the optical signal of the second frequency modulation photoelectric circuit can enter the corresponding reflector for independent reflection, and then be entered into the multimode optical delay line together by the third mode converter in the form of mode multiplexing for secondary delay. This method can avoid the interference caused by reflecting multiple signals at the same time, reduce the signal reflection loss, and improve the signal quality reflected back to the multimode optical delay line.

[0023] In another example of structure two, the mode conversion element further includes a second optical transmission element and a third mode converter. The second optical transmission element is connected between the beam splitter of the second frequency-modulated optoelectronic circuit, the mixer in the second frequency-modulated optoelectronic circuit, and the first end of the third mode converter. The second end of the third mode converter is coupled to a second position of the optical delay line, which is located between the second mode converter and the second end of the optical delay line. The second optical transmission element is used to transmit the second optical signal from the beam splitter in the second frequency-modulated optoelectronic circuit to the third mode converter, and to transmit the delayed signal from the third mode converter to the mixer in the second frequency-modulated optoelectronic circuit. The third mode converter is used to convert the second optical signal from the second optical transmission element into a higher-order mode signal in the optical delay line and couple it into the optical delay line at the second position, and to convert the higher-order mode signal after two delays in the optical delay line into a delayed signal in the second frequency-modulated optoelectronic circuit and couple it out to the second optical transmission element at the second position. The reflection element is also used to reflect the higher-order mode signal after the initial delay in the optical delay line back to the optical delay line.

[0024] Based on the above example, by setting a second optical transmission element, a third mode converter, and a reflection element, the optical signal in the second frequency-modulated optoelectronic circuit can be smoothly coupled into the optical delay line, and the optical signal after the second delay can be smoothly coupled out of the optical delay line, while maintaining the opposite transmission direction to the optical signal in the first frequency-modulated optoelectronic circuit, so as to use the same optical delay line to transmit the optical signals in the two frequency-modulated optoelectronic circuits back and forth in opposite directions.

[0025] In a further example, the reflective element includes a fourth mode converter and a second reflector. One end of the fourth mode converter is connected to the second reflector, and the other end is coupled to a first position of the optical delay line. The first position is located between the first mode converter and the first end of the optical delay line. The fourth mode converter is used to convert the high-order mode signal after the initial delay of the optical delay line into the initial delayed signal in the second frequency-modulated optoelectronic circuit and couple it out to the second reflector at the first position. It is also used to convert the initial delayed signal reflected back by the second reflector into a high-order mode signal in the optical delay line and couple it out to the optical delay line at the first position.

[0026] Based on the above example, a unique reflector can be set for the second frequency modulation photoelectric circuit so that the optical signal of the second frequency modulation photoelectric circuit can enter the corresponding reflector for independent reflection, and then be reversed by the third mode converter in the form of mode multiplexing to enter the multimode optical delay line for secondary delay. This reduces the signal reflection loss and improves the signal quality reflected back to the multimode optical delay line.

[0027] In one example of structure two, the optical transmission element has a first end, a second end, and a third end. The transmission from the first end to the second end and from the second end to the third end is unidirectional. The first end is connected to the beam splitter in the corresponding frequency modulation optoelectronic circuit, the second end is connected to the first mode converter or the third mode converter in the corresponding frequency modulation optoelectronic circuit, and the third end is connected to the mixer in the corresponding frequency modulation optoelectronic circuit.

[0028] Based on the above examples, the unidirectional transmission characteristics of the three ports of the optical transmission element can be used to allow as much of the signal to be delayed as possible to enter the optical delay line for delay processing, and to allow as much of the delayed optical signal as possible to enter the mixer, thereby improving the signal delay effect and mixing effect.

[0029] In one example of Structure 2, the optical transmission element is a circulator. Circulators have low cost, small size, and are easy to implement.

[0030] In one example of structure two, the reflector can be a waveguide loop back reflector, a Bragg grating, or a sagnac ring, which are relatively inexpensive devices.

[0031] In one example of structure one or structure two, there are N second frequency-modulated optoelectronic circuits. The N first positions corresponding to the N second frequency-modulated optoelectronic circuits are arranged sequentially between the first mode converter and the first end of the optical delay line. The cross-sectional dimensions of the optical delay line are different at the N first positions.

[0032] Based on the above example, by coupling N third-mode converters at different positions on one side of the first end of the multimode optical delay line, the signals to be delayed in the N second frequency-modulated optoelectronic circuits can be converted into N higher-order mode signals in the multimode optical delay line. Furthermore, by designing the multimode optical delay line to have different cross-sectional dimensions at different positions, it is possible to support N higher-order mode signals of different orders based on the different cross-sectional dimensions.

[0033] In a further example, the cross-sectional dimensions of the optical delay line at the N first positions show an increasing trend.

[0034] Based on the above example, the cross-sectional size of the multimode optical delay line increases sequentially on one side of the first end, and the supported mode spot size also increases sequentially. This increasing mode spot size can support the sequential reception of N signals to be delayed from N second frequency-modulated optoelectronic circuits. The later these signals are coupled in, the higher the order of the coupled signal. This structural design can minimize the size of the multimode optical delay line on one side of the first end while ensuring good coupling efficiency on that side.

[0035] In one example of Structure 1 or Structure 2, there are N second frequency-modulated optoelectronic circuits. The N second positions corresponding to the N second frequency-modulated optoelectronic circuits are arranged sequentially between the second mode converter and the second end of the optical delay line. The cross-sectional dimensions of the optical delay line are different at the N second positions.

[0036] Based on the above example, by coupling N fourth-mode converters at different positions on one side of the second end of the multimode optical delay line, the N higher-order mode signals delayed by the multimode optical delay line can be converted into N delayed signals in the N second frequency-modulated optoelectronic circuits and output to their respective mixers. Furthermore, by designing the multimode optical delay line to have different cross-sectional dimensions at different positions, it is possible to support the output of N higher-order mode signals of different orders based on the different cross-sectional dimensions.

[0037] In a further example, the cross-sectional dimensions of the optical delay line at the N second positions show an increasing trend.

[0038] Based on the above example, the cross-sectional dimensions of the multimode optical delay line decrease sequentially on one side of the second end, and the supported mode spot sizes also decrease sequentially. These progressively smaller mode spot sizes can support the sequential output of N delayed signals from N second frequency-modulated optoelectronic circuits. The later these delayed signals are output, the lower the signal order. This structural design minimizes the size of the multimode optical delay line on the second side while ensuring good output efficiency on that side.

[0039] In one example of Structure 1 or Structure 2, an adiabatic mode converter is positioned between any two adjacent positions in any of the N first positions and / or any two adjacent positions in any of the N second positions. In some scenarios, the adiabatic mode converter is also referred to as a cone mode converter.

[0040] Based on the above examples, by using an adiabatic mode converter to convert the fundamental or higher-order mode signals, a relatively high-purity conversion mode can be achieved, while also having a large operating bandwidth and low insertion loss.

[0041] In one example of Structure 1 or Structure 2, the first and second mode converters are adiabatic mode converters, and the third and fourth mode converters are directional couplers.

[0042] Based on the above examples, adiabatic mode converters and directional couplers have relatively high transmission or coupling efficiency, which can reduce the loss of optical signals during transmission and conversion between optical delay lines and preceding and following optical components, thereby improving conversion efficiency.

[0043] In any of the above structures or examples, the optical delay line is either a fiber optic delay line or a waveguide delay line integrated on a chip. Thus, the signal processing device can be adapted to various optical delay lines, thereby achieving versatility.

[0044] In any of the above structures or examples, each frequency-modulated optoelectronic circuit further includes a target measurement path. The beam splitter has a first output terminal, a second output terminal, and a third output terminal. The first output terminal is connected to a mode conversion element, the second output terminal is connected to a mixer, and the third output terminal is connected to the target measurement path. Based on this structure and connection, the beam splitter is used to separate the signal to be delayed, the local oscillator signal, and the probe signal from the optical signal output from the light source. The signal to be delayed is output through the first output terminal, the local oscillator signal is output through the second output terminal, and the probe signal is output through the third output terminal. The mixer is used to perform frequency mixing processing on the local oscillator signal and the delayed signal. The target measurement path is used to perform target measurement using the probe signal.

[0045] Based on the above, the signal processing device can not only calibrate the modulation signal output by the drive circuit, but also perform target measurement. By calibrating the frequency modulation signal output by the drive circuit, the frequency of the light signal emitted by the light source can change linearly with time, thereby making the detection signal obtained based on the light signal meet the preset requirements, thus improving the accuracy of target detection in the target measurement path.

[0046] Optionally, the N frequency-modulated photoelectric circuits may share the same target measurement path, or each circuit may have its own target measurement path, or some may share the same target measurement path and some may have their own target measurement paths.

[0047] Based on the above design, the signal processing device can be applied to various situations with or without a shared target measurement path. By sharing the target measurement path, the detection signals from multiple frequency-modulated photoelectric circuits can be combined into a single signal for simultaneous target measurement. This not only reduces the number of target measurement paths that need to be set up, saving on component costs and space, but also increases the power of the detection signal for the measured target.

[0048] Optionally, the beam splitting element includes a first beam splitter and a second beam splitter. The first output terminal of the first beam splitter is connected to the input terminal of the second beam splitter, the second output terminal of the first beam splitter is connected to the target measurement path, the first output terminal of the second beam splitter is connected to a mode conversion element, and the second output terminal of the second beam splitter is connected to a mixer. Based on this structure and connection relationship, the first beam splitter is used to split the optical signal output from the light source into a probe signal and an intermediate optical signal, outputting the intermediate optical signal through its first output terminal and the probe signal through its second output terminal. The second beam splitter is used to split the intermediate optical signal into a local oscillator signal and a signal to be delayed, outputting the signal to be delayed through its first output terminal and the local oscillator signal through its second output terminal.

[0049] Based on the above design, the function of the beam splitting element can be realized by two beam splitters. The beam splitters are low in cost and small in size, which helps to realize the small size and low cost of the signal processing device.

[0050] In any of the above structures or examples, each frequency-modulated photoelectric circuit further includes an amplifier and / or an analog-to-digital converter (ADC), which is connected between the mixer and the light source. Taking the inclusion of an amplifier and an ADC as an example, the amplifier amplifies the intermediate frequency (IF) signal from the photodetector element, and the ADC performs analog-to-digital conversion on the IF signal or the amplified IF signal to obtain a digital signal.

[0051] Based on the above design, the power of the intermediate frequency signal is amplified by an amplifier, which ensures that the intermediate frequency signal is successfully transmitted to the analog-to-digital converter. The intermediate frequency signal is then sampled into a digital signal by the analog-to-digital converter, which facilitates subsequent software analysis.

[0052] In one possible design, each frequency-modulated optoelectronic circuit also includes a photodetector, a processing element, and a driving circuit. The photodetector is used to detect the intermediate frequency signal obtained by the mixer; the processing element is used to generate a feedback signal based on the intermediate frequency signal detected by the photodetector; and the driving circuit is used to calibrate the linearity between the modulation signal output to the light source and the light signal output by the light source based on the feedback signal generated by the processing element.

[0053] Optionally, when the device includes both an amplifier and / or an analog-to-digital converter, as well as a photodetector element, a processing element, and a driving circuit, the amplifier and / or the analog-to-digital converter is connected between the photodetector element and the processing element.

[0054] Secondly, this application provides a detection device, including the signal processing device described in the first aspect or any of the designs, examples or implementations of the first aspect.

[0055] Thirdly, this application provides a terminal device that includes the signal processing apparatus described in the first aspect or any of the designs, examples or implementations of the first aspect, or includes the detection apparatus described in the second aspect.

[0056] The technical effects that can be achieved by the second or third aspect mentioned above can be referred to the description of the beneficial effects in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0057] Figure 1a illustrates an exemplary schematic diagram of the linear relationship between the emitted beam and the modulated signal;

[0058] Figure 1b illustrates an exemplary schematic diagram of the nonlinear relationship between the emitted beam and the modulated signal;

[0059] Figure 1c illustrates a schematic diagram of a Sagnac loop reflector;

[0060] Figure 2 illustrates a possible application scenario to which this application applies;

[0061] Figure 3a illustrates an exemplary schematic diagram of a mainstream direct-modulation FMCWLiDAR architecture;

[0062] Figure 3b illustrates a schematic diagram of the structure of a single-laser direct-modulated FMCWLiDAR provided in the industry.

[0063] Figure 3c illustrates a schematic diagram of the structure of a direct-modulation FMCWLiDAR with multiple lasers provided in the industry.

[0064] Figure 4 illustrates a schematic diagram of the structure of a signal processing device provided in this application;

[0065] Figure 5 illustrates a schematic diagram of another signal processing device provided in this application;

[0066] Figure 6 illustrates a schematic diagram of the structure of a signal processing device provided in Embodiment 1;

[0067] Figure 7 illustrates a schematic diagram of another signal processing device provided in Embodiment 1;

[0068] Figure 8 illustrates a partially enlarged structural diagram of a mode converter and optical delay line provided in Implementation Scheme 1;

[0069] Figure 9 illustrates a schematic diagram of a signal processing device provided in Embodiment 2;

[0070] Figure 10 illustrates a schematic diagram of another signal processing apparatus provided in Embodiment 2;

[0071] Figure 11 exemplarily shows a partially enlarged structural diagram of a mode converter and optical delay line provided in Embodiment 2;

[0072] Figure 12 illustrates a schematic diagram of a signal processing apparatus provided in Embodiment 3;

[0073] Figure 13a illustrates a schematic diagram of another signal processing device provided in Embodiment 2;

[0074] Figure 13b illustrates a schematic diagram of another signal processing device provided in Embodiment 2;

[0075] Figure 14 illustrates a schematic diagram of another signal processing apparatus provided in Embodiment 3;

[0076] Figure 15 exemplarily illustrates a partially enlarged structural diagram of a mode converter and optical delay line provided in Embodiment 3;

[0077] Figure 16 illustrates a schematic diagram of a signal processing apparatus provided in Embodiment 4;

[0078] Figure 17 illustrates a schematic diagram of another signal processing apparatus provided in Embodiment 4;

[0079] Figure 18 exemplarily illustrates a partially enlarged structural diagram of a mode converter and optical delay line provided in Embodiment 4;

[0080] Figure 19a illustrates a schematic diagram of the structure of yet another signal processing apparatus provided in this application;

[0081] Figure 19b illustrates a schematic diagram of another signal processing apparatus provided in this application;

[0082] Figure 20a illustrates a schematic diagram of the structure of yet another signal processing apparatus provided in this application;

[0083] Figure 20b illustrates a schematic diagram of another signal processing apparatus provided in this application;

[0084] Figure 21a illustrates a schematic diagram of another signal processing apparatus provided in this application;

[0085] Figure 21b illustrates a schematic diagram of another signal processing device provided in this application;

[0086] Figure 21c exemplarily illustrates a structural schematic diagram of another signal processing apparatus provided in this application;

[0087] Figure 21d illustrates a schematic diagram of another signal processing apparatus provided in this application;

[0088] Figure 22 illustrates a schematic diagram of the structure of a detection device provided in this application;

[0089] Figure 23 illustrates a schematic diagram of the structure of a terminal device provided in this application. Detailed Implementation

[0090] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0091] The following provides explanations for some of the terms used in this application. It should be noted that these explanations are for the convenience of those skilled in the art and do not constitute a limitation on the scope of protection claimed in this application.

[0092] I. Waveguide Loop Reflector

[0093] A waveguide loop reflector is a structure that reflects a light beam by fabricating a waveguide into a loop. Examples of waveguide loop reflectors include, but are not limited to: linear loop mirrors (OLMs), non-linear loop mirrors (NOLMs), non-linear amplifying loop mirrors (NALMs), figure-eight fiber optic reflectors, and Sagnac loop reflectors (SLRs).

[0094] Taking an SLR as an example, Figure 1c shows a possible structural diagram of an SLR. This SLR includes a ring and a beam splitter. The beam splitter has one port on the left and two ports on the right, which are connected together by waveguides to form the ring. If a beam of light U is input to the left port of the beam splitter, it will be split into two beams, U1 and U2. These two beams, U1 and U2, propagate in opposite directions within the ring and eventually return to the beam splitter. At this point, the beam splitter becomes a beam combiner, combining the two beams U1 and U2 into a single beam U3, which is then output from the left port.

[0095] Based on the beam propagation principle of SLR (Single-Lens Resonator), two beams, U1 and U2, propagate in opposite directions simultaneously within the ring. Due to the interference properties of light, when the two beams U1 and U2 meet in the ring, they form a stable intensity distribution within the overlap region. However, because the beams themselves propagate independently, once they leave the overlap region, they revert to their original motion states. In other words, the interfering light can be separated into the two beams U1 and U2 before they interfered, and each beam continues to propagate with its original frequency, direction, and phase. Therefore, SLR has a good reflection effect, ensuring that the reflected light signal still has good quality.

[0096] II. Bragg Grating

[0097] A Bragg grating, also known as a distributed Bragg reflector (DBR), is designed based on the property that the reflectivity of light at the interface of different media is related to the magnitude of the refractive index between the media. By periodically stacking thin films with different refractive indices, when light passes through these films, the light reflected back from each layer undergoes constructive interference due to changes in phase angle, thus combining to produce strong reflected light. DBRs are commonly used in waveguides.

[0098] III. Single-mode waveguides and multimode waveguides

[0099] A single-mode waveguide is a waveguide in which light can propagate in only one mode. This propagation mode is called the fundamental mode. Therefore, it can also be considered that only the fundamental mode of light is transmitted in a single-mode waveguide, while all higher-order modes of the light wave are cut off. Different types of waveguides can have different single-mode conditions. Achieving the single-mode condition can avoid multimode interference and signal distortion, making waveguide transmission more stable and reliable.

[0100] Conversely, a multimode waveguide is a waveguide that allows light to propagate in multiple modes. Among these multiple propagation modes, there is a fundamental mode and at least one higher-order mode. The fundamental mode is also called the dominant mode, and the higher-order modes are also called higher-order modes. When multiple higher-order modes exist, their orders are different.

[0101] IV. Frequency mixing.

[0102] Frequency mixing, also known as coherent demodulation, refers to the difference between the frequencies and phases of two signals. In FMCW LiDAR, the probe signal is typically a linear frequency modulated (LFM) signal. After this LFM signal interacts with the target object, the reflected echo signal (i.e., the received signal) will also have the same frequency variation characteristics. However, depending on the distance to the target, the echo signal will have a certain phase and frequency difference relative to the probe signal. Therefore, after receiving the echo signal, the echo signal and the probe signal can be mixed, that is, the frequency and phase of the probe signal and the echo signal are differed to obtain a low-frequency beat signal, also known as the beat frequency signal or intermediate frequency (IF) signal. The IF signal contains information about the frequency difference between the two signals, which is related to the target distance. For example, in a static state, the absolute value of the frequency difference is proportional to the target distance. In a dynamic state, the IF signal also contains information about the Doppler effect caused by the target's movement, and the target's velocity can be calculated based on this Doppler effect information.

[0103] The preceding text introduced some of the terms used in this application. The following text introduces the possible application scenarios of this application.

[0104] In one possible implementation, the signal processing device provided in this application can be integrated into a detection device, which can be installed on a vehicle, including but not limited to: vehicles, ships, airplanes, drones, trains, subways, automated guided vehicles (AGVs), or unmanned vehicles. For example, please refer to Figure 2, which illustrates a possible application scenario of this application. In this scenario, the detection device is installed on the front bumper of a vehicle. This detection device can serve as an information source for path planning, assisting the driver in achieving or automatically achieving safe driving. It is understood that the detection device can also be installed in other locations on the vehicle, such as around the headlights, around the rearview mirrors, near the doors, on the rear bumper, behind the windshield, or on the roof, to capture information about the vehicle's surrounding environment. When the detection device is installed behind the windshield, the requirement for no gravel collision risk is lower, and it does not affect the vehicle's appearance. Furthermore, the windshield itself has window heating and defogging functions as well as wiper cleaning functions.

[0105] It should be understood that the above application scenarios are merely examples, and the detection device provided in this application can also be applied to other possible scenarios, not limited to those listed above. For example, the detection device can also be installed in a roadside unit (RSU) as a roadside traffic detection device to realize intelligent vehicle-road cooperative communication. For example, the detection device can also be installed in the cabin of a vehicle as a liveness detection device to detect and alert the user to children or pets left behind in the cabin. Furthermore, the detection device can also be applied to terminal devices or components of terminal devices, such as smartphones, smart home devices, smart manufacturing equipment, medical devices, industrial equipment, and robots. These will not be listed exhaustively here. Moreover, the detection device can also be applied to…

[0106] It should be noted that the application scenarios described in this application are for the purpose of more clearly illustrating the technical solutions of this application, and do not constitute a limitation on the technical solutions provided in this application.

[0107] In addition, the above-mentioned application scenarios can be applied to fields such as autonomous driving, assisted driving, intelligent driving, autonomous driving, connected vehicles, optical communication, security monitoring, biomedicine, surveying and mapping (such as 3D mapping and remote sensing mapping), meteorological research, biomass and vegetation research, air quality monitoring, and aviation and aerospace applications.

[0108] The detection devices mentioned above may include, but are not limited to, LiDAR, such as a direct-modulation FMCW LiDAR, or simply direct-modulation FMCW LiDAR. Before introducing the specific solution provided in this application, the relevant content of direct-modulation FMCW LiDAR will be introduced below.

[0109] Figure 3a shows a schematic diagram of a mainstream direct-modulation FMCWLiDAR architecture. This direct-modulation FMCWLiDAR includes a light source, a beam splitter, a target measurement path, a reference calibration path, and a driving circuit. The reference calibration path is connected to one output terminal of the beam splitter, and the target measurement path is connected to the other output terminal. During operation, the driving circuit generates a modulation signal (L1) and inputs it to the light source. This modulation signal L1 drives the light source to emit a light signal R whose frequency changes linearly with time. The beam splitter separates the light signal R into a probe signal and a calibration signal. The probe signal is output to the target measurement path, and the calibration signal is output to the reference calibration path. The target measurement path performs target measurement based on the probe signal to obtain information such as the target's distance and velocity. The reference calibration path generates a feedback signal (P) based on the calibration signal and outputs the feedback signal P to the driving circuit. The driving circuit calibrates the output modulation signal L1 based on the feedback signal P, ensuring that the frequency change of the light signal R emitted by the light source is linear with the input modulation signal L1.

[0110] For example, taking a laser as the light source and beam splitter 1 as the beam splitter element, please refer to Figure 3b, which shows a specific structural schematic diagram of a direct-modulated FMCWLiDAR with a single laser. In this example, the reference calibration path may include beam splitter 2, optical delay line, mixer, photodetector, and processing element. The laser emits a laser signal R according to the modulation signal L1 input to the driving circuit. Beam splitter 1 splits the laser signal R into a detection signal and a calibration signal. The detection signal is input to the target measurement path for target measurement, and the calibration signal is input to beam splitter 2. Beam splitter 2 splits the calibration signal into a signal light to be delayed and a local oscillator light of the calibration path. The local oscillator light of the calibration path is directly input to the mixer, while the signal light to be delayed is also input to the mixer after being delayed by the optical delay line. The mixer mixes the local oscillator light of the calibration path and the delayed signal light to obtain an intermediate frequency (IF) signal. The photodetector detects the IF signal and inputs the detected IF signal to the processing element. The processing element processes the IF signal to obtain a feedback signal P, and inputs the feedback signal P to the driving circuit. The driving circuit adjusts the modulation signal L1 output to the laser based on the input feedback signal P.

[0111] Based on the single-laser direct-modulation FMCWLiDAR architecture shown in Figure 3b, the structure is extended to a multi-laser scenario, as shown in Figure 3c. It can be seen that in a multi-laser direct-modulation FMCWLiDAR, multiple optical delay lines are required, and the number of delay lines corresponds one-to-one with the number of lasers. Therefore, if extended to a direct-modulation FMCWLiDAR with N (N≥2) lasers, the length of the optical delay lines needs to be N times the length of the delay lines in a single-laser direct-modulation FMCWLiDAR. In a single-laser direct-modulation FMCWLiDAR, the length of the optical delay line is related to the required delay time, typically on the order of meters. This length is already quite long; if extended to N lasers, multiplying the meter-level delay lines by N results in a very large size and high hardware cost, occupying a significant amount of space within the FMCWLiDAR.

[0112] In view of this, this application provides a signal processing apparatus that sets the optical delay line as a multimode optical delay line and uses a mode converter to convert optical signals in multiple frequency-modulated optoelectronic circuits into multiple modes in the multimode optical delay line. This allows for mode multiplexing, sharing the same multimode optical delay line to delay the optical signals in multiple frequency-modulated optoelectronic circuits. When applied to a direct-modulated FMCW LiDAR with multiple lasers, multiple reference calibration paths corresponding to multiple lasers can share the same optical delay line, significantly reducing the number of optical delay lines, lowering their size and hardware cost, and correspondingly reducing the space occupied by the optical delay line in the direct-modulated FMCW LiDAR.

[0113] The signal processing device and related contents proposed in this application will be described in detail below with reference to Figures 4 to 23.

[0114] It should be noted that in the accompanying drawings of this application, two devices are connected by a "dashed line," indicating that the two devices are connected through an optical medium, such as an optical fiber, waveguide, or any medium capable of transmitting optical signals. In short, two devices connected by a "dashed line" can transmit optical signals. Similarly, two devices are connected by a "solid line," indicating that the two devices are connected through an electrical medium (also called an electrical connection), such as a cable, wire, or any medium capable of transmitting electrical signals. In short, two devices connected by a "solid line" can transmit electrical signals.

[0115] Furthermore, in this application, "connection of two components" refers to two components being directly connected, such as by optical fiber or waveguide. "Coupling," on the other hand, refers to two components being close enough, without direct contact, to allow for directional transmission of optical signals.

[0116] Furthermore, the mode converter devices shown in the various figures of this application are merely examples, and this application does not limit the mode converter to be implemented only by the shapes or devices shown in the figures. Any other curved or non-curved shapes, or any other structure of mode multiplexers or mode demultiplexers, as long as they can achieve the function of the mode converter in this application, are also within the scope of protection of this application.

[0117] Please refer to Figure 4, which shows a schematic diagram of a signal processing device provided in this application. The signal processing device includes a first frequency-modulated photoelectric circuit 110 and a second frequency-modulated photoelectric circuit 210. Each frequency-modulated photoelectric circuit includes a light source, a beam splitter, a mode conversion element 300, an optical delay line 400, a mixer, a photodetector, a processing element, and a driving circuit. For example, the first frequency-modulated photoelectric circuit 110 includes a light source 111, a beam splitter 112, a mode conversion element 300, an optical delay line 400, a mixer 114, a photodetector 115, a processing element 116, and a driving circuit 117; the second frequency-modulated photoelectric circuit 210 includes a light source 211, a beam splitter 212, a mode conversion element 300, an optical delay line 400, a mixer 214, a photodetector 215, a processing element 216, and a driving circuit 217.

[0118] As shown in Figure 4, the first frequency-modulated optoelectronic circuit 110 and the second frequency-modulated optoelectronic circuit 210 share the same mode conversion element 300 and the same optical delay line 400. The optical delay line 400 supports optical signal transmission in at least two modes and can also be called a multimode optical delay line. Based on this multimode optical delay line, as shown in Figure 4, the first optical signal S after being split by the beam-splitting element 112 in the first frequency-modulated optoelectronic circuit 110... 11 The second optical signal S after being split by the beam splitter 212 in the second frequency-modulated photoelectric circuit 210 21 All signals are input to mode conversion element 300, which converts the first optical signal S... 11 Second optical signal S 21 The signal is output to the optical delay line 400 in different modes for delay processing, and the first optical signal S after delay processing is then output to the optical delay line 400 for delay processing. 11 The original mode output from the first frequency modulation photoelectric circuit 110 is sent to the mixer 114 in the first frequency modulation photoelectric circuit 110, and the delayed optical signal S from the second frequency modulation photoelectric circuit 210 is used to... 21 The output is in the original mode of the second frequency modulation photoelectric circuit 210 and sent to the mixer 214 in the second frequency modulation photoelectric circuit 210.

[0119] Based on this, the optical signal S in the two frequency-modulated photoelectric circuits 11 S 21The signals will be transmitted on the same optical delay line 400, thus allowing the same optical delay line 400 to be reused to transmit the optical signals S in the two frequency-modulated optoelectronic circuits. 11 and S 21 The delay processing reduces the number of optical delay lines required in the signal processing device, thereby reducing the cost and space occupied by optical delay lines. Furthermore, due to the optical signal S in the two frequency-modulated optoelectronic circuits... 11 and S 21 Different modes are input to the optical delay line 400, and the signals are output to their respective mixers in their original modes. Therefore, without affecting their respective mixing operations, the optical signal S in the two frequency-modulated optoelectronic circuits can be reduced by mode-based beam splitting. 11 and S 21 The mutual interference during the delay processing results in the delayed optical signal S output to the mixers in the two frequency modulation optoelectronic circuits. 11 'and S 21 It can have better signal quality and improve the signal calibration effect in each frequency modulation optoelectronic circuit.

[0120] It should be noted that the optical signal S in the two frequency-modulated photoelectric circuits 11 S 21 It can be an optical signal with completely identical characteristics, such as optical signals with the same frequency, wavelength, phase, and emission time; or it can be an optical signal with at least one different characteristic, such as optical signals with different wavelengths, different phases, different frequencies, or different emission times. Although the two optical signals S 11 S 21 Both will be transmitted on the same optical delay line 400, but they are input to the optical delay line 400 in different modes. Therefore, even if the characteristics of the two optical signals are exactly the same, the two optical signals S after delay processing will be different. 11 'and S 21 'It can also be separated from the optical delay line 400 based on different modes and returned to their respective frequency modulation optoelectronic circuits, which will have little impact on the functionality of the two frequency modulation optoelectronic circuits.'

[0121] In a signal processing device, a frequency-modulated photoelectric circuit can be understood as a loop formed by the signal transmission between its various internal components. For example, taking the first frequency-modulated photoelectric circuit 110 as an example, as shown in Figure 4, its signal transmission process is as follows: the optical signal S1 output by the light source 111 enters the beam splitter 112; the beam splitter 112 splits the optical signal S1 into the first optical signal S... 11 Other optical signals (not shown in the figure, see Figure 5 below for details); First optical signal S 11After being converted into a signal of a certain mode by the mode conversion element 300 (such as the fundamental mode signal or higher-order mode signal of a multimode optical delay line), the signal is input to the optical delay line 400 for delay processing. The first optical signal S after delay processing... 11 The signal is converted to the original mode in the first frequency modulation photoelectric circuit 110 by the mode conversion element 300 and output to the mixer 114. In the mixer 114, it is mixed with other signals (not shown in the figure, but can be seen in Figure 5 below) to obtain the intermediate frequency signal Z1. The intermediate frequency signal Z1 is detected by the photodetector element 115 and output to the processing element 116. The processing element 116 sends a feedback signal P1 to the drive circuit 117 according to the detected intermediate frequency signal Z1. The drive circuit 117 adjusts the modulation signal L1 output to the light source 111 according to the feedback signal P1 to calibrate the linearity between the modulation signal L1 and the light signal S1 output by the light source 111.

[0122] In the above description, other optical signals may include local oscillator signals. For example, please refer to Figure 5, which shows a schematic diagram of another signal processing device provided in this application. Taking the first frequency-modulated photoelectric circuit 110 as an example, as shown in Figure 5, in one example, the beam splitter 112 may have an input terminal and a first output terminal c. 11 Second output terminal c 12 The mixer 114 may have an output terminal and a first input terminal d. 11 Second input terminal d 12 The mode conversion element 300 is connected to the first output terminal c of the beam splitter 112. 11 The first input terminal d of mixer 114 11 Between the optical delay line 400 and the light delay line. For example, the input terminal of the beam splitter 112 is connected to the light source 111, and the first output terminal c 11 Connect one end of the mode conversion element 300, and the second output terminal c 12 Connect to the second input terminal d of mixer 114 12 The first input terminal d of mixer 114 11 The other end of the mode conversion element 300 is connected, and the other end of the mode conversion element 300 is connected to the optical delay line 400.

[0123] Based on this structure and connection, the optical signal S1 output by the light source 111 enters the beam splitter 112; the beam splitter 112 performs beam splitting processing on the optical signal S1 to obtain the first optical signal S 11 The calibration path local oscillator signal is transmitted through the first output terminal c. 11 Output the first optical signal S 11 And through the second output terminal c 12 The output calibration path local oscillator signal is directly input to the second input terminal d of mixer 114. 12 The first optical signal S11 The signal is first converted to a certain mode by mode conversion element 300 and then transmitted to optical delay element 400 for delay processing. After that, it is converted back to the original mode by mode conversion element 300 and enters the first input terminal d of mixer 114. 11 Mixer 114 has a first input terminal d 11 The first optical signal S received after delay processing 11 ' and second input terminal d 12 The received calibration path local oscillator signal is mixed to obtain the intermediate frequency signal Z1.

[0124] Optionally, as shown in Figure 5, each frequency-modulated optoelectronic circuit may further include an amplifier and / or an analog-to-digital converter (ADC). For example, the first frequency-modulated optoelectronic circuit 110 may further include an amplifier 118 and / or an ADC 119, and the second frequency-modulated optoelectronic circuit 210 may further include an amplifier 218 and / or an ADC 219. Taking the first frequency-modulated optoelectronic circuit 110 as an example, as shown in Figure 5, when the amplifier 118 is included, the amplifier 118 can be connected between the photodetector element 115 and the processing element 116 to amplify the intermediate frequency signal Z1 detected by the photodetector element 115. When the ADC 119 is included, the ADC 119 can be connected between the photodetector element 115 and the processing element 116 to perform analog-to-digital conversion on the intermediate frequency signal Z1 detected by the photodetector element 115 to obtain a digital signal. When both amplifier 118 and analog-to-digital converter 119 are included, amplifier 118 and analog-to-digital converter 119 can be connected in series between photodetector 115 and processing element 116. Amplifier 118 can amplify the intermediate frequency signal Z1 detected by photodetector 115, and then input the amplified intermediate frequency signal Z1 to analog-to-digital converter 119. Analog-to-digital converter 119 performs analog-to-digital conversion on the amplified intermediate frequency signal Z1 to obtain a digital signal, and then inputs the digital signal to processing element 116.

[0125] Optionally, as shown in Figure 5, each frequency-modulated photoelectric circuit may further include a target measurement path. For example, the first frequency-modulated photoelectric circuit 110 may also include a target measurement path 113, and the second frequency-modulated photoelectric circuit 210 may also include a target measurement path 213. Target measurement path 113 and target measurement path 213 may be the same target measurement path or different target measurement paths, without limitation. Taking the first frequency-modulated photoelectric circuit 110 as an example, as shown in Figure 5, in one example, the beam splitter 112 may also have a third output terminal c. 13 The third output terminal c 13 Connected to target measurement path 113. Beam splitter 112 performs beam splitting processing on the optical signal S output from light source 111, obtaining the first optical signal S. 11In addition to the calibration local oscillator signal, a detection signal can also be obtained. The beam splitter 112 outputs the signal through the third output terminal c. 13 The output probe signal is received by the target measurement path 113, which performs target measurement based on the received probe signal. The specific implementation of the target measurement path will be described below and will not be explained here.

[0126] Taking the structure of the signal processing device shown in Figure 5 as an example, the optical signals in the two frequency-modulated photoelectric circuits 110 are input into the same optical delay line 400 for delay processing. The two optical signals can be transmitted in the same direction or in opposite directions in the optical delay line 400. Based on implementation scheme one and implementation scheme two, the possible implementation methods of transmission in the same direction and transmission in opposite directions are introduced below.

[0127] Implementation Plan 1

[0128] Here, implementation scheme one corresponds to a scheme in which at least two optical signals are transmitted in the same direction in the same optical delay line 400.

[0129] Please refer to Figure 6, which shows a schematic diagram of a signal processing device provided in Embodiment 1. Referring to Figure 6 and Figure 5 above, for the first frequency-modulated photoelectric circuit 110, the mode conversion element 300 may include a first mode converter 310 and a second mode converter 320. The first mode converter 310 is connected between the beam splitter 112 in the first frequency-modulated photoelectric circuit 110 and the first end a1 of the optical delay line 400. The second mode converter 320 is connected between the mixer 114 in the first frequency-modulated photoelectric circuit 110 and the second end a2 of the optical delay line 400. The first mode converter 310 receives the first optical signal S after it has been split by the beam splitter 112 in the first frequency-modulated photoelectric circuit 110. 11 Then, the first optical signal S can be... 11 The signal is converted into a fundamental mode signal in the optical delay line 400 and output. This fundamental mode signal enters from the first end a1 of the optical delay line 400, undergoes propagation delay within the optical delay line 400, and is output from the second end a2 of the optical delay line 400, then enters the second mode converter 320. The second mode converter 320 can convert the delayed fundamental mode signal into a delayed first optical signal S in the first frequency-modulated optoelectronic circuit 110. 11 ', and output to mixer 114 in the first frequency modulation photoelectric circuit 110.

[0130] To achieve the above functionality, in one example, as shown in Figure 6, one end of the first mode converter 310 can be connected to the first output terminal c of the beam splitter 112 via a single-mode fiber or a single-mode waveguide. 11The other end is connected to the first end a1 of the optical delay line 400. One end of the second mode converter 320 can be connected to the first input end d of the mixer 114 via a single-mode fiber or a single-mode waveguide. 11 The other end is connected to the second end a2 of the optical delay line 400. Based on this connection, the first optical signal S after being split by the beam splitter 112... 11 The first optical signal S is input to the first mode converter 310 in the fundamental mode form of a single-mode fiber or a single-mode waveguide. The first mode converter 310 converts the first optical signal S into a single-mode optical signal. 11 The signal is converted to the fundamental mode form of a multimode fiber or multimode waveguide and output to the optical delay line 400. After being delayed by the optical delay line 400, the fundamental mode signal enters the second mode converter 320 in the fundamental mode form of a multimode fiber or multimode waveguide. The second mode converter 320 converts the delayed fundamental mode signal into the fundamental mode form of a single-mode fiber or single-mode waveguide and outputs it to the mixer 114 to participate in the mixing operation in the first frequency modulation optoelectronic circuit 110.

[0131] Optionally, referring to Figure 6 and Figure 5 above, for the second frequency-modulated photoelectric circuit 210, the mode conversion element 300 may include a third mode converter 331 and a fourth mode converter 341. One end of the third mode converter 331 is connected to the beam splitter 212 in the second frequency-modulated photoelectric circuit 210, and the other end is coupled to the first position K of the optical delay line 400. 11 First position K 11 Located between the first mode converter 310 and the first end a1 of the optical delay line 400. One end of the fourth mode converter 341 is connected to the mixer 214 in the second frequency modulation optoelectronic circuit 210, and the other end is coupled to the second position K of the optical delay line 400. 21 The second position K 21 Located between the second mode converter 320 and the second end a2 of the optical delay line 400. The third mode converter 320 receives the second optical signal S after it has been split by the beam splitter 212 in the second frequency modulation optoelectronic circuit 210. 21 Then, the second optical signal S can be... 21 It is converted into a higher-order mode signal of the optical delay line 400 and output. This higher-order mode signal starts from the first position K. 11 Coupled into the optical delay line 400, after the propagation delay in the optical delay line 400, at the second position K of the optical delay line 400. 21 The signal is coupled out and enters the fourth mode converter 341. The fourth mode converter 341 converts the delayed high-order mode signal into the delayed second optical signal S in the second frequency-modulated optoelectronic circuit 210. 21 ', and output to mixer 214 in the second frequency modulation photoelectric circuit 210.

[0132] To achieve the above functionality, in one example, as shown in Figure 6, one end of the third mode converter 331 can be connected to the first output terminal i of the beam splitter 212 via a single-mode fiber or a single-mode waveguide. 11 The other end is coupled to the first position K of the optical delay line 400. 11 One end of the fourth mode converter 341 can be connected to the first input terminal d of the mixer 214 via a single-mode fiber or a single-mode waveguide. 21 The other end is coupled to the second position K of the optical delay line 400. 21 Based on this connection and coupling relationship, the second optical signal S after being split by the beam splitter 212... 21 The second optical signal S is input to the third mode converter 331 in the form of the fundamental mode of a single-mode fiber or a single-mode waveguide. The third mode converter 331 converts the second optical signal S into its fundamental mode. 21 Converted to a higher-order mode form of multimode fiber or multimode waveguide, and at the first position K 11 The signal is coupled to optical delay line 400. The higher-order mode signal, after being delayed by optical delay line 400, enters the fourth mode converter 341 in the form of a higher-order mode in a multimode fiber or multimode waveguide. The fourth mode converter 341 converts the delayed higher-order mode signal into the fundamental mode form of a single-mode fiber or single-mode waveguide, and sets it at position K. 21 It is coupled out to mixer 214 to participate in the mixing operation in the second frequency modulation optoelectronic circuit 210.

[0133] Using the structure shown in Figure 6, the first optical signal S 11 The signal can be converted into the fundamental mode signal of the optical delay line 400 by the first mode converter 310 and then directly enters the optical delay line 400, while the second optical signal S... 12 Then, after being converted into a higher-order mode signal of the optical delay line 400 by the third mode converter 331, it is placed at the first position K. 11 The signal is coupled into the optical delay line 400 and propagates along with the fundamental mode signal within the optical delay line 400, reaching the second end a2 of the optical delay line 400. Subsequently, the higher-order mode signal is located at the second position K of the optical delay line 400. 21 The signal is coupled out and converted by the fourth mode converter 341 into the delayed signal of the original mode in the second frequency modulation photoelectric circuit 210. It is then mixed with the local oscillator signal of the calibration path in the second frequency modulation photoelectric circuit 210. The fundamental mode signal continues to be transmitted to the second mode converter 320, where it is converted into the delayed signal of the original mode in the first frequency modulation photoelectric circuit 110. It is then mixed with the local oscillator signal of the calibration path in the first frequency modulation photoelectric circuit 110.

[0134] Based on this, the structure shown in Figure 6 can share the same optical delay line to transmit optical signals in two frequency-modulated optoelectronic circuits in the same direction. However, this structure can also be extended to signal processing devices with three or more frequency-modulated optoelectronic circuits, so that the three or more frequency-modulated optoelectronic circuits share the same optical delay line 400 to transmit optical signals in the three or more frequency-modulated optoelectronic circuits in the same direction.

[0135] For example, please refer to Figure 7, which shows a structural diagram of another possible signal processing device provided in Implementation Scheme 1. This structure can share the same optical delay line 400 to transmit optical signals in N+1 frequency-modulated optoelectronic circuits in the same direction, where N is a positive integer greater than or equal to 2.

[0136] As shown in Figure 7, the signal processing device may include a first frequency-modulated photoelectric circuit 110 and N second frequency-modulated photoelectric circuits, namely second frequency-modulated photoelectric circuit 210, second frequency-modulated photoelectric circuit 220, ..., second frequency-modulated photoelectric circuit 2N0. The N second frequency-modulated photoelectric circuits 210 to 2N0 have identical structures. The structure of the first frequency-modulated photoelectric circuit 110 and the structure of each second frequency-modulated photoelectric circuit can be found in Figure 6 above. For example, the first frequency-modulated photoelectric circuit 110 includes the light source 111, beam splitter 112, first mode converter 310, optical delay line 400, second mode converter 320, mixer 114, photodetector 115, amplifier 118, analog-to-digital converter 119, processing element 116, drive circuit 117, and target measurement path 113 described above. The second frequency-modulated photoelectric circuit 210 includes the light source 211, beam splitter 212, third mode converter 331, optical delay line 400, fourth mode converter 341, mixer 214, photodetector 215, amplifier 218, analog-to-digital converter 219, processing element 216, drive circuit 217, and target measurement path 213, as described above. Similarly, the second frequency-modulated photoelectric circuit 220 includes the light source 221, beam splitter 222, third mode converter 332, optical delay line 400, fourth mode converter 342, mixer 224, photodetector 225, amplifier 228, analog-to-digital converter 229, processing element 226, drive circuit 227, and target measurement path 223. ... The second frequency modulation optoelectronic circuit 2N0 includes a light source 2N1, a beam splitter 2N2, a third mode converter 33N, an optical delay line 400, a fourth mode converter 34N, a mixer 2N4, a photodetector 2N5, an amplifier 2N8, an analog-to-digital converter 2N9, a processing element 2N6, a drive circuit 2N7, and a target measurement path 2N3.

[0137] Please refer to Figure 8, which shows a partially enlarged structural view of each mode converter and optical delay line 400 in Figure 7. Combining Figures 7 and 8: On the input side of the optical delay line 400, the first mode converter 310 is connected between the beam splitter 112 in the first frequency modulation optoelectronic circuit 110 and the first end a1 of the optical delay line 400. One end of each of the N third mode converters 331 to 33N is connected to one of the N beam splitters 212 to 2N2 in the N second frequency modulation optoelectronic circuits 210 to 2N0, and the other end is coupled to one of the N first positions K of the optical delay line 400. 11 ~K 1N For example, one end of the third mode converter 331 is connected to the beam splitter 212 in the second frequency modulation optoelectronic circuit 210, and the other end is coupled to the first position K of the optical delay line 400. 11 One end of the third mode converter 332 is connected to the beam splitter 222 in the second frequency modulation optoelectronic circuit 220, and the other end is coupled to the first position K of the optical delay line 400. 12 And so on. One end of the third mode converter 33N is connected to the beam splitter 2N2 in the second frequency modulation optoelectronic circuit 2N0, and the other end is coupled to the first position K of the optical delay line 400. 1N .

[0138] Optionally, N first positions K 11 ~K 1N The optical delay line 400 is arranged sequentially between the first mode converter 310 and the first end a1 of the optical delay line 400, with the optical delay line 400 at N first positions K. 11 ~K 1N The cross-sectional dimensions are different. For example, in one example, as shown in Figure 8, the optical delay line 400 has N first positions K. 11 ~K 1N The cross-sectional dimensions show an increasing trend. That is to say, at the N first positions K... 11 ~K 1N In the middle, optical delay line 400 is at the first position K. 11 The cross-sectional dimension is the smallest at the first position K. 12 The cross-sectional dimensions are greater than those at the first position K. 11 Large, in the first position K 13 The cross-sectional dimensions are greater than those at the first position K. 12 Big, ..., in the first position K 1N The cross-sectional dimensions are greater than those at the first position K. 1N-1 Large. Optionally, the first position K 1N The cross-sectional dimensions of the optical delay line 400 are the same as those of the first end a1. Thus, as seen from left to right in Figure 8, the closer to the first end a1, the larger the cross-sectional dimensions of the optical delay line 400, and the more optical signal modes the optical delay line 400 can accommodate.

[0139] Based on this structure, in each frequency-modulated optoelectronic circuit, the beam splitter processes the optical signal generated by the light source to obtain a detection signal, a calibration path local oscillator signal, and a signal to be delayed. The detection signal is input to the target measurement path for target measurement, the calibration path local oscillator signal is input to the mixer, and the signal to be delayed is input to the connected mode converter. In the first frequency-modulated optoelectronic circuit 110, the signal to be delayed is the first optical signal S. 11 First optical signal S 11 The signal is input to the first mode converter 310, where it is converted from the fundamental mode of a single-mode fiber or waveguide to the fundamental mode of a multimode fiber or waveguide and output to the optical delay line 400. In the second frequency-modulated optoelectronic circuit 210, the signal to be delayed is the second optical signal S. 21 The second optical signal S 21 The input is fed to the third mode converter 331, which converts the fundamental mode of the single-mode fiber or single-mode waveguide into a higher-order mode (called the first-order mode) of the multimode fiber or multimode waveguide, and stores it at the first position K of the optical delay line 400. 11 The signal is coupled into the optical delay line 400. In the second frequency-modulated optoelectronic circuit 220, the signal to be delayed is the second optical signal S. 22 The second optical signal S 22 The input is fed to the third mode converter 332, which converts the fundamental mode of the single-mode fiber or single-mode waveguide into a higher-order mode (called the second-order mode) of the multimode fiber or multimode waveguide, and stores it at the first position K of the optical delay line 400. 12 The signal is coupled into the optical delay line 400. ... In the second frequency-modulated optoelectronic circuit 2N0, the signal to be delayed is the second optical signal S. 2N The second optical signal S 2N The input is fed to the third mode converter 33N, which converts the fundamental mode of the single-mode fiber or single-mode waveguide into the highest-order mode (called the Nth-order mode) of the multimode fiber or multimode waveguide, and stores it at the first position K of the optical delay line 400. 1N The optical signals are coupled into the optical delay line 400 at the same point. In this way, N+1 different modes of optical signals will be input into the optical delay line 400 on the same side, and after being transmitted in the same direction in the optical delay line 400, they will reach the other end of the optical delay line 400, namely the second end a2.

[0140] Similarly, on the output side of the optical delay line 400, the second mode converter 320 is connected between the mixer 114 in the first frequency modulation optoelectronic circuit 110 and the second end a2 of the optical delay line 400, while one end of each of the N fourth mode converters 341 to 34N is connected to one of the N mixers 214 to 2N4 in the N second frequency modulation optoelectronic circuits 210 to 2N0, and the other end is coupled to one of the N second positions K of the optical delay line 400. 21 ~K 2NFor example, one end of the fourth mode converter 341 is connected to the mixer 214 in the second frequency modulation optoelectronic circuit 210, and the other end is coupled to the second position K of the optical delay line 400. 21 One end of the fourth mode converter 342 is connected to the mixer 224 in the second frequency modulation optoelectronic circuit 220, and the other end is coupled to the second position K of the optical delay line 400. 22 Similarly, one end of the fourth mode converter 34N is connected to the mixer 2N4 in the second frequency modulation optoelectronic circuit 2N0, and the other end is coupled to the second position K of the optical delay line 400. 2N .

[0141] Optionally, N second positions K 21 ~K 2N The optical delay line 400 is arranged sequentially between the second mode converter 320 and the second end a2 of the optical delay line 400, with the optical delay line 400 at N second positions K. 21 ~K 2N The cross-sectional dimensions are different. For example, in one example, as shown in Figure 8, the optical delay line 400 has N second positions K. 21 ~K 2N The cross-sectional dimensions show an increasing trend. That is to say, at the N second positions K... 21 ~K 2N In the middle, optical delay line 400 is at the second position K. 21 The cross-sectional dimension is the smallest at the second position K. 22 The cross-sectional dimension is greater than that of the second position K 21 Large, in the second position K 23 The cross-sectional dimension is greater than that of the second position K 22 Large, ..., in the second position K 2N The cross-sectional dimension is greater than that of the second position K 2N-1 Large. Optionally, the second position K 2N The cross-sectional dimensions of the optical delay line 400 are the same as those of the second end a2. Thus, viewed from right to left in Figure 8, the closer to the second end a2, the larger the cross-sectional dimensions of the optical delay line 400, and the more optical signal modes the optical delay line 400 can accommodate.

[0142] Based on this structure, N+1 different optical modes are delayed by the optical delay line 400 and then transmitted to the second end a2 of the optical delay line 400. The Nth-order mode optical signal of the multimode fiber or multimode waveguide is located at position K on the second end of the optical delay line 400. 2N The signal is coupled out and converted into the fundamental mode signal of a single-mode fiber or waveguide by the fourth mode converter 34N. It then enters the mixer 2N4 and is mixed with the local oscillator signal of the calibration path in the second frequency modulation opto-circuit 2N0 to obtain the intermediate frequency signal in the second frequency modulation opto-circuit 2N0. Similarly, the second-order mode optical signal of the multimode fiber or waveguide is at the second position K of the optical delay line 400.22 The signal is coupled out and converted into the fundamental mode signal of a single-mode fiber or waveguide by the fourth mode converter 342. It then enters the mixer 224 and is mixed with the local oscillator signal of the calibration path in the second frequency-modulated optoelectronic circuit 220 to obtain the intermediate frequency signal in the second frequency-modulated optoelectronic circuit 220. The first-order mode optical signal of the multimode fiber or waveguide is located at the second position K of the optical delay line 400. 21 The signal is coupled out and converted into the fundamental mode signal of a single-mode fiber or single-mode waveguide by the fourth mode converter 341. It then enters mixer 214 and is mixed with the local oscillator signal of the calibration path in the second frequency-modulated optoelectronic circuit 210 to obtain the intermediate frequency signal in the second frequency-modulated optoelectronic circuit 210. Meanwhile, the fundamental mode signal of the multimode fiber or multimode waveguide is directly transmitted to the second mode converter 320, converted into the fundamental mode signal of a single-mode fiber or single-mode waveguide, and then enters mixer 114. It is then mixed with the local oscillator signal of the calibration path in the first frequency-modulated optoelectronic circuit 110 to obtain the intermediate frequency signal in the first frequency-modulated optoelectronic circuit 110.

[0143] For a multimode optical delay line 400, the larger the cross-sectional size of the optical signal coupling position, the higher the order in the optical delay line 400. In the example above, by setting the first position K... 21 ~K 2N The cross-sectional dimensions increase sequentially, and the second position K 21 ~K 2N The cross-sectional dimensions increase sequentially, allowing for the expansion of the cross-sectional dimensions at each location where an optical signal needs to be coupled in to accommodate the signal, and the reduction of the cross-sectional dimensions at each location where an optical signal needs to be coupled out to reduce the volume. This structure can satisfy the transmission of optical signals in N+1 modes while reducing waste in size, volume, and cost, making it the most effective.

[0144] However, it should be understood that other structural designs can also be adopted. For example, the cross-sectional size of the optical delay line 400 on the input side can be set to gradually increase in a curved form, with some areas increasing in a diagonal form and some areas increasing in a curved form, some areas increasing in a diagonal or curved form and some areas remaining unchanged or decreasing, and / or, on the output side, the cross-sectional size can be set to gradually decrease in a curved form, with some areas decreasing in a diagonal form and some areas decreasing in a curved form, some areas decreasing in a diagonal or curved form and some areas remaining unchanged or increasing. These structures can also achieve optical signal coupling in and out, but there will be a small amount of signal waste.

[0145] Optionally, the first mode converter 310 and / or the second mode converter 320 described above can be adiabatic mode converters, which are those indicated by the symbols in Figure 7 or Figure 8. and The components represented here. Adiabatic mode converters can reduce mode conversion losses by gradually increasing or decreasing the size of the device's cross-sectional area. For example, low-loss mode conversion of the input optical signal can be achieved by gradually increasing the cross-sectional area on the input side, and low-loss mode conversion of the output optical signal can be achieved by gradually decreasing the cross-sectional area on the output side. The longer the range of cross-sectional area change in the adiabatic mode converter, the lower the mode conversion loss.

[0146] Optionally, any of the N third mode converters 331 to 33N and the N fourth mode converters 341 to 34N can be a coupler, such as a directional coupler, which refers to the symbol in Figure 7 or Figure 8. and The directional coupler represents a component that, while not in direct contact with the optical delay line 400, is sufficiently close to it to achieve coupled transmission of optical signals between the directional coupler and the optical delay line 400 with minimal transmission loss. Furthermore, the directional coupler has a simple structure and low cost.

[0147] Optionally, the optical delay line 400 has N first positions K 11 ~K 1N Any two adjacent positions and / or the second position K in 21 ~K 2N An adiabatic mode converter is positioned between any two adjacent locations within the optical circuit. Thus, the optical signal to be delayed in any second frequency-modulated optoelectronic circuit, after being coupled to the optical delay line 400 via a directional coupler, can be converted into a higher-order mode signal on the optical delay line 400 with low loss via an adiabatic mode converter. Furthermore, the higher-order mode signal on the optical delay line 400, after being delayed, is first converted into a delayed signal in the second frequency-modulated optoelectronic circuit with low loss via an adiabatic mode converter, and then coupled into the second frequency-modulated optoelectronic circuit via a directional coupler. This allows for efficient optical signal coupling and mode conversion between the second frequency-modulated optoelectronic circuit and the optical delay line 400.

[0148] Based on the structure shown in Figure 7, the optical signals in the N+1 frequency-modulated optoelectronic loops can be transmitted in the same direction along the same optical delay line. Therefore, the N+1 frequency-modulated optoelectronic loops can share the same optical delay line for delay processing based on mode multiplexing. This not only reduces the number of optical delay lines required in the signal processing device but also maintains the same delay time for the optical signal in each frequency-modulated optoelectronic loop, achieving a minimally simplistic architecture and extremely low cost for the signal processing device. Furthermore, all components in the above signal processing device can be implemented on a chip; therefore, the above structure can also achieve chip-level integration for the multiplexing of optical delay lines.

[0149] It should be noted that Figures 6 and 7 above are only examples of N+1 frequency-modulated photoelectric circuits each having their own separate target measurement path. However, in other examples, N+1 frequency-modulated photoelectric circuits may share the same target measurement path, or some frequency-modulated photoelectric circuits may share the same target measurement path, while other frequency-modulated photoelectric circuits may have their own separate target measurement paths. This application does not make any specific limitations on this.

[0150] Furthermore, although the optical signals in the N+1 frequency-modulated optoelectronic circuits propagate in the same direction along the same optical delay line, these optical signals have different modes, and these different modes are independent of each other. Therefore, these optical signals can be directly and accurately split based on different modes, and multiple optical signals do not need to have wavelength differences. In other words, the optical signals in the N+1 frequency-modulated optoelectronic circuits can have the same wavelength.

[0151] Implementation Plan 2

[0152] Here, implementation scheme two corresponds to a scheme in which at least two optical signals are transmitted in reverse on the same optical delay line 400.

[0153] Please refer to Figure 9, which shows a schematic diagram of a signal processing device provided in Embodiment 2. Similar to Embodiment 1 above, the mode conversion element 300 also includes a first mode converter 310, a second mode converter 320, a third mode converter 331, and a fourth mode converter 341. The structure, connection relationship with other components, and functions of the first mode converter 310 and the second mode converter 320 are the same as those in Embodiment 1 above, and will not be repeated here.

[0154] Unlike the first embodiment described above, as shown in Figure 9, one end of the third mode converter 331 is connected to the beam splitter 212 in the second frequency modulation photoelectric circuit 210, while the other end is coupled to the second position K of the optical delay line 400. 21 The second position K 21 Located between the second mode converter 320 and the second end a2 of the optical delay line 400. One end of the fourth mode converter 341 is connected to the mixer 214 in the second frequency modulation optoelectronic circuit 210, and the other end is coupled to the first position K of the optical delay line 400. 11 First position K 11 Located between the first mode converter 310 and the first end a1 of the optical delay line 400. The third mode converter 320 receives the second optical signal S after it has been split by the beam splitter 212 in the second frequency-modulated optoelectronic circuit 210. 21 Then, the second optical signal S 21 It is converted into a higher-order mode signal of optical delay line 400 and output. This higher-order mode signal is located at position K. 21Coupled into the optical delay line 400, after the propagation delay in the optical delay line 400, at the first position K of the optical delay line 400. 11 The signal is coupled out and enters the fourth mode converter 341. The fourth mode converter 341 converts the delayed high-order mode signal into the delayed second optical signal S in the second frequency-modulated optoelectronic circuit 210. 21 ', and output to mixer 214 in the second frequency modulation photoelectric circuit 210.

[0155] Based on the above structure, as shown in Figure 9, assuming that the first mode converter 310 and the beam splitter 112, the second mode converter 320 and the mixer 114, the third mode converter 331 and the beam splitter 212, and the fourth mode converter 341 and the mixer 214 are all connected through single-mode optical fiber or single-mode waveguide, then: in the first frequency modulation optoelectronic circuit 110, the first optical signal S after being split by the beam splitter 112... 11 The signal is input to the first mode converter 310 in the fundamental mode form of a single-mode fiber or single-mode waveguide. The first mode converter 310 converts it to the fundamental mode form of a multimode fiber or multimode waveguide and outputs it to the first end a1 of the optical delay line 400. It then propagates to the right in the optical delay line 400 to the second end a2, and enters the second mode converter 320. The second mode converter 320 converts it to the fundamental mode form of a single-mode fiber or single-mode waveguide and then enters the mixer 114. Meanwhile, in the second frequency-modulated optoelectronic circuit 210, the second optical signal S, after being split by the beam splitter 212... 21 The fundamental mode of a single-mode fiber or waveguide is input to the third mode converter 331, where it is converted into a higher-order mode of a multimode fiber or waveguide. Then, at the second position K... 21 Coupled into optical delay line 400, propagating to the left in optical delay line 400 to the first position K of optical delay line 400. 11 The output is coupled out and enters the fourth mode converter 341, where it is converted into the fundamental mode of a single-mode fiber or a single-mode waveguide before entering the mixer 214.

[0156] Based on this, the structure shown in Figure 9 can share the same optical delay line to transmit optical signals in two frequency-modulated optoelectronic circuits in reverse. However, this structure can also be extended to signal processing devices with three or more frequency-modulated optoelectronic circuits, so that the three or more frequency-modulated optoelectronic circuits share the same optical delay line 400 to transmit optical signals in the three or more frequency-modulated optoelectronic circuits in reverse.

[0157] For example, please refer to Figure 10, which shows a structural diagram of another possible signal processing device provided in Implementation Scheme 2. This structure can share the same optical delay line 400 to transmit optical signals in N+1 frequency-modulated optoelectronic circuits in reverse, where N is a positive integer greater than or equal to 2.

[0158] Similar to Implementation Scheme 1, as shown in Figure 10, N+1 frequency modulation photoelectric circuits refer to one first frequency modulation photoelectric circuit 110 and N second frequency modulation photoelectric circuits 210 to 2N0. The first frequency modulation photoelectric circuit 110 corresponds to the first mode converter 310 and the second mode converter 320, and the N second frequency modulation photoelectric circuits 210 to 2N0 correspond to N third mode converters 331 to 33N and N fourth mode converters 341 to 34N.

[0159] Figure 11 shows a partially enlarged structural view of each mode converter and optical delay line 400 in Figure 10. Combining Figures 10 and 11: On the input side, the first mode converter 310 is connected between the beam splitter 112 in the first frequency modulation optoelectronic circuit 110 and the first end a1 of the optical delay line 400. One end of each of the N third mode converters 331 to 33N is connected to one of the N beam splitters 212 to 2N2 in the N second frequency modulation optoelectronic circuits 210 to 2N0, and the other end is coupled to one of the N second positions K of the optical delay line 400. 21 ~K 2N N first positions K 21 ~K 2N They are sequentially arranged between the second mode converter 320 and the second end a2 of the optical delay line 400. Optionally, the optical delay line 400 has N second positions K 21 ~K 2N The cross-sectional dimensions are different. For example, in one example, as shown in Figure 11, the optical delay line 400 has N second positions K. 21 ~K 2N The cross-sectional size shows an increasing trend. Thus, in Figure 11, from right to left, the closer to the second end a2, the larger the cross-sectional size of the optical delay line 400, and the more optical signal modes the optical delay line 400 can accommodate.

[0160] Similarly, on the output side, as shown in Figure 11, the second mode converter 320 is connected between the mixer 114 in the first frequency modulation optoelectronic circuit 110 and the second end a2 of the optical delay line 400. One end of each of the N fourth mode converters 341-34N is connected to one of the N mixers 214-2N4 in the N second frequency modulation optoelectronic circuits 210-2N0, and the other end is coupled to one of the N first positions K of the optical delay line 400. 11 ~K 1N N first positions K 11 ~K 1N They are sequentially arranged between the first mode converter 310 and the first end a1 of the optical delay line 400. Optionally, the optical delay line 400 has N first positions K 11 ~K 1NThe cross-sectional dimensions are different. For example, in one example, as shown in Figure 11, the optical delay line 400 has N first positions K. 11 ~K 1N The cross-sectional size shows an increasing trend. Thus, in Figure 11, from left to right, the closer to the first end a1, the larger the cross-sectional size of the optical delay line 400, and the more optical signal modes the optical delay line 400 can accommodate.

[0161] Based on this structure and connection, in each frequency-modulated optoelectronic circuit, the beam splitter processes the optical signal generated by the light source to obtain a detection signal, a calibration path local oscillator signal, and a signal to be delayed. The detection signal is input to the target measurement path for target measurement, the calibration path local oscillator signal is input to the mixer, and the signal to be delayed is input to the connected mode converter. In the first frequency-modulated optoelectronic circuit 110, the signal to be delayed is the first optical signal S. 11 First optical signal S 11 The signal is input to the first mode converter 310, where it is converted from the fundamental mode of a single-mode fiber or waveguide to the fundamental mode of a multimode fiber or waveguide. The signal is then output to the first end a1 of the optical delay line 400, and subsequently transmitted from left to right in the optical delay line 400 to the second end a2. There, it is converted from the fundamental mode of a multimode fiber or waveguide to the fundamental mode of a single-mode fiber or waveguide by the second mode converter 320, and then output to the mixer 114 in the first frequency modulation optoelectronic circuit 110.

[0162] In the second frequency-modulated photoelectric circuit 210, the signal to be delayed is the second optical signal S. 21 The second optical signal S 21 The input is fed to the third mode converter 331, where it converts the fundamental mode of the single-mode fiber or single-mode waveguide into the first-order mode of the multimode fiber or multimode waveguide, and then sets the input at the second position K. 21 The signal is coupled into the optical delay line 400 and then propagates from right to left within the optical delay line 400, reaching the first end a1 of the optical delay line 400. In the second frequency-modulated optoelectronic circuit 220, the signal to be delayed is the second optical signal S. 22 The second optical signal S 22 The input is fed to the third mode converter 332, where it is converted from the fundamental mode of the single-mode fiber or single-mode waveguide to the second-order mode of the multimode fiber or multimode waveguide, and then set at the second position K. 22 The signal is coupled into the optical delay line 400 and then propagates from right to left within the optical delay line 400, reaching the first end a1 of the optical delay line 400. ... In the second frequency-modulated optoelectronic circuit 2N0, the signal to be delayed is the second optical signal S. 2N The second optical signal S 2NThe input is fed to the third mode converter 33N, where it converts the fundamental mode of the single-mode fiber or single-mode waveguide into the Nth-order mode of the multimode fiber or multimode waveguide, and then sets the K-mode at the second position. 2N It is coupled into the optical delay line 400 and then propagates from right to left in the optical delay line 400, reaching the first end a1 of the optical delay line 400.

[0163] Furthermore, the Nth-order mode optical signal of the multimode fiber or multimode waveguide is transmitted to the first position K of the optical delay line 400. 1N After being converted into a single-mode optical signal by the fourth mode converter 34N, the signal is coupled out and enters the mixer 2N4 in the second frequency-modulated optoelectronic circuit 2N0. Similarly, the second-order mode optical signal of the multimode optical fiber or multimode waveguide is transmitted to the first position K of the optical delay line 400. 12 After being converted into a single-mode optical signal by the fourth mode converter 342, the signal is coupled out and enters the mixer 224 in the second frequency-modulated optoelectronic circuit 220. The first-order mode optical signal of the multimode optical fiber or multimode waveguide is transmitted to the first position K of the optical delay line 400. 11 After being converted into a single-mode optical fiber or single-mode waveguide optical signal by the fourth mode converter 341, it is coupled out and enters the mixer 214 in the second frequency modulation optoelectronic circuit 210.

[0164] Based on the structure shown in Figure 10, in the N+1 frequency-modulated optoelectronic circuits, the optical signal in one frequency-modulated optoelectronic circuit is input to the optical delay line 400 at the first end a1 and transmitted to the second end a2 of the optical delay line 400 before being output. Meanwhile, the optical signals in the other N frequency-modulated optoelectronic circuits are input to the optical delay line 400 at the second end a2 and transmitted to the first end a1 of the optical delay line 400 before being output. These N+1 optical signals are divided into two groups and transmitted in opposite directions within the optical delay line 400. Based on this, the N+1 frequency-modulated optoelectronic circuits can also share the same optical delay line for delay processing based on mode multiplexing. This not only allows for chip-level integration of optical delay line multiplexing but also reduces the number of optical delay lines required in the signal processing device, without reducing the delay time of the optical signals from the N+1 frequency-modulated optoelectronic circuits. This enables a simplified architecture and extremely low cost for the signal processing device.

[0165] Based on Scheme 1 and Scheme 2 above, a single delay processing of the optical signal to be delayed can be achieved. Optionally, in other schemes, a reflective element can be introduced into the signal processing device to achieve two or more delays of the signal to be delayed. Taking two delays as an example, based on Scheme 3 and Scheme 4, two more possible schemes are provided below.

[0166] Implementation Plan 3

[0167] Here, implementation scheme 3 corresponds to a scheme in which at least two optical signals are transmitted back and forth in the same direction on the same optical delay line 400.

[0168] Please refer to Figure 12, which shows a schematic diagram of a signal processing device provided in Embodiment 3. In addition to the first frequency-modulated photoelectric circuit 110 and the second frequency-modulated photoelectric circuit 120, the signal processing device also includes a reflective element 600, which is connected to the second end a2 of the optical delay line.

[0169] Optionally, referring to Figure 12 and Figure 5 above, for the first frequency-modulated photoelectric circuit 110, the mode conversion element 300 may include a first optical transmission element 510 and a first mode converter 310. The first optical transmission element 510 is connected between the beam splitter 112, the mixer 114, and the first end (left end in the figure) of the first mode converter 310. The second end (right end in the figure) of the first mode converter 310 is connected to the first end a1 of the optical delay line 400. The first optical transmission element 510 can transmit the first optical signal S after beam splitting by the beam splitter 112. 11 The signal is transmitted to the first mode converter 310. The first mode converter 310 converts the first optical signal S... 11 The signal is converted into a fundamental mode signal in the optical delay line 400 and output. This fundamental mode signal enters from the first end a1 of the optical delay line 400, undergoes a first propagation delay in the optical delay line 400, and is output from the second end a2 of the optical delay line 400. It then enters the reflective element 600, is reflected by the reflective element 600, returns to the second end a2 of the optical delay line 400, undergoes a second propagation delay in the optical delay line 400, and is output from the first end a1 of the optical delay line 400, entering the first mode converter 310. The first mode converter 310 converts the fundamental mode signal after the second delay into a delayed signal S in the first frequency-modulated photoelectric circuit 110. 11 The signal S is then output to the first optical transmission element 510. The first optical transmission element 510 will then output the delayed signal S. 11 "Transmitted to mixer 114."

[0170] To achieve the above functions, in one example, as shown in Figure 12, the first optical transmission element 510 can have three ends, namely the first end e 11 The second end e 12 and the third end e 13 The first end e 11 The first output terminal c of the beam splitter 112 is connected 11 The second end e 12 The diagram shows the left end of the first mode converter 310 connected to the third terminal e. 13 Connect the first input terminal d of mixer 114 11 The first end e 11 To the second end e 12 The second end e12 To the third end e 13 It is a unidirectional transmission. Based on this design, the first output terminal c of the beam splitter 112... 11 The first output optical signal S 11 It will enter the first end e of the first optical transmission element 510 11 Because of the first end e 11 To the second end e 12 It is a unidirectional transmission; therefore, the first optical signal S 11 It will be from the second end e of the first optical transmission element 510 12 The output enters the left end of the diagram of the first mode converter 310. Assume the left end of the diagram of the first mode converter 310 is connected to the second end e of the first optical transmission element 510. 12 If they are connected by single-mode fiber or single-mode waveguide, then the first optical signal S 11 The optical fiber or waveguide can be converted from its fundamental mode form by the first mode converter 310 to its fundamental mode form by the first mode converter 310, and output to the first end a1 of the optical delay line 400. It then travels from left to right to the second end a2 of the optical delay line 400, is output to the reflector 600, is reflected back to the second end a2 of the optical delay line 400, travels from right to left back to the first end a1 of the optical delay line 400, and is then output to the first mode converter 310. The first mode converter 310 converts the optical fiber or waveguide back to its fundamental mode form by the first mode converter 310, and the optical fiber or waveguide returns to the second end e of the first optical transmission element 510. 12 Because of the second end e 12 To the third end e 13 It is a unidirectional transmission; therefore, the optical signal will originate from the third terminal e of the first optical transmission element 510. 13 The output is sent to mixer 114 to participate in the mixing operation in the first frequency modulation photoelectric circuit 110.

[0171] Similarly, referring to Figure 12 and Figure 5 above, for the second frequency-modulated optoelectronic circuit 210, the mode conversion element 300 may include a second optical transmission element 521 and a third mode converter 331. The second optical transmission element 520 is connected between the beam splitter 212, the mixer 214, and the first end (left end in the figure) of the third mode converter 331. The second end (right end in the figure) of the third mode converter 331 is coupled to the first position K of the optical delay line 400. 11 First position K 11 Located between the first mode converter 310 and the first end a1 of the optical delay line 400. The second optical transmission element 520 can transmit the second optical signal S after it has been split by the beam splitter 212. 21 The signal is transmitted to the third mode converter 331. The third mode converter 331 converts the second optical signal S... 21It is converted into a higher-order mode signal in the optical delay line 400 and output. This higher-order mode signal starts from the first position K. 11 The signal is coupled into the optical delay line 400, undergoes a propagation delay within the optical delay line 400, and is output at the second end a2 of the optical delay line 400. It then enters the reflecting element 600, is reflected by the reflecting element 600, returns to the second end a2 of the optical delay line 400, undergoes a second propagation delay within the optical delay line 400, and then exits at the first position K. 11 The optical delay line 400 is coupled out and enters the third mode converter 331. The third mode converter 331 converts the higher-order mode signal after the second delay into the delayed signal S in the second frequency-modulated optoelectronic circuit 210. 21 The signal S is then output to the second optical transmission element 521. The second optical transmission element 521 will then output the delayed signal S. 21 "Transmitted to mixer 214."

[0172] To achieve the above functions, in one example, as shown in Figure 12, the second optical transmission element 521 can have three ends, namely the first end e 21 The second end e 22 and the third end e 23 The first end e 21 The first output terminal i of the beam splitter 212 is connected 11 The second end e 22 The left end of the diagram connecting the third mode converter 331, the third terminal e 23 Connect the first input terminal d of mixer 214 21 The first end e 21 To the second end e 22 The second end e 22 To the third end e 23 It is unidirectional transmission. Based on this connection and coupling relationship, the first output terminal i of the beam splitter 212 11 The output second optical signal S 21 It will enter the first end e of the second optical transmission element 521 21 Because of the first end e 21 To the second end e 22 It is a unidirectional transmission; therefore, the second optical signal S 21 It will be from the second end e of the second optical transmission element 521 22 The output enters the left end of the diagram of the third mode converter 331. Assume the left end of the diagram of the third mode converter 331 is connected to the second end e of the second optical transmission element 521. 22 If they are connected by single-mode fiber or single-mode waveguide, then the second optical signal S 21 It can be converted from the fundamental mode of a single-mode fiber or single-mode waveguide to a higher-order mode of a multimode fiber or multimode waveguide by a third mode converter 331, and at the first position K 11The light is coupled into the optical delay line 400, and then transmitted from left to right to the second end a2 of the optical delay line 400, output to the reflective element 600, reflected back to the second end a2 of the optical delay line 400 by the reflective element 600, and then transmitted from right to left back to the first position K. 11 The coupled optical delay line 400 is then output to the third mode converter 331, where it is converted into the fundamental mode of a single-mode fiber or single-mode waveguide and returned to the second terminal e of the second optical transmission element 521. 22 Because of the second end e 22 To the third end e 23 It is a unidirectional transmission; therefore, the optical signal will originate from the third terminal e of the second optical transmission element 521. 23 The output is sent to mixer 214 to participate in the mixing operation in the second frequency modulation optoelectronic circuit 210.

[0173] Using the structure shown in Figure 12, by setting up optical transmission elements and reflection elements, the optical signal in each frequency modulation optoelectronic circuit can be used in both the forward and reverse directions through a mode converter, sharing the same optical delay line to achieve two delay processing. Under the same delay duration requirement, the length of the optical delay line can be further shortened to half of the original length, further reducing the cost and size of the signal processing device.

[0174] Optionally, the first optical transmission element 510 and / or the second optical transmission element 521 can be any device with at least three ports and unidirectional transmission between ports. For example, it can be a circulator as shown in Figure 12, an isolator, or a coupler. Although the coupler cannot completely transmit the optical signal after the second delay to the mixer, by setting the interference parameters of each port on the coupler, the input and output signals of each port can be proportionally adjusted, thereby ensuring that most of the optical signal after the second delay is transmitted to the mixer. Of course, the optical transmission element may be other devices, which are not specifically limited here.

[0175] Optionally, the aforementioned reflective element 600 may include only one reflector, which is directly connected to the second end a2 of the optical delay line 400 to reflect the optical signals in multiple frequency-modulated photoelectric circuits transmitted from the optical delay line 400 together. Alternatively, it may include multiple reflectors, each corresponding to a frequency-modulated photoelectric circuit, and each reflector is used to reflect the optical signal in its corresponding frequency-modulated photoelectric circuit.

[0176] Taking the latter as an example, please refer to Figure 13a, which shows a schematic diagram of another signal processing device provided in Embodiment 3. In this example, for the first frequency-modulated optoelectronic circuit 110, the reflective element 600 may include a second mode converter 320 and a first reflector 610. The second mode converter 320 is connected between the second end a2 of the optical delay line 400 and the first reflector 610. Assuming that the second mode converter 320 and the first reflector 610 are also connected through a single-mode fiber or a single-mode waveguide, the fundamental mode signal of the multimode fiber or multimode waveguide after the initial delay by the optical delay line 400 will be output at the second end a2 of the optical delay line 400, enter the second mode converter 320, be converted into a single-mode fiber or single-mode waveguide fundamental mode signal by the second mode converter 320, enter the first reflector 610, and then be reflected back to the second mode converter 320. After passing through the second mode converter 320 in the reverse direction, it is converted back into a multimode fiber or multimode waveguide fundamental mode signal and enters the optical delay line 400 for a second delay.

[0177] Similarly, for the second frequency-modulated optoelectronic circuit 210, the reflective element 600 may include a fourth mode converter 341 and a second reflector 621. One end of the fourth mode converter 341 (right end in the figure) is connected to the second reflector 621, and the other end (left end in the figure) is coupled to the second position K of the optical delay line 400. 21 The second position K 21 Located between the second mode converter 320 and the second end a2 of the optical delay line 400. Assuming the fourth mode converter 341 and the second reflector 621 are also connected via single-mode fiber or single-mode waveguide, then the higher-order mode signal of the multimode fiber or multimode waveguide after the initial delay by the optical delay line 400 will be at the second position K of the optical delay line 400. 21 The signal is coupled out and enters the fourth mode converter 341. After being converted into the fundamental mode signal of a single-mode fiber or single-mode waveguide by the fourth mode converter 341, it enters the second reflector 621 and is reflected back to the fourth mode converter 341. After passing through the fourth mode converter 341 in the reverse direction, it is converted back into a higher-order mode signal of a multimode fiber or multimode waveguide and is then placed at the second position K. 21 A 400-degree optical delay line is inserted for a second delay.

[0178] The first reflector 610 and / or the second reflector 621 can be any element capable of reflecting optical signals, such as, but not limited to, a mirror, a Sagnac ring reflector, or a Bragg grating. For example, taking a Sagnac ring reflector as an example, as shown in Figure 13b, the first reflector 610 can specifically include a beam splitter 611 and a loopback 612. One end of the beam splitter 611 is connected to the second end a2 of the optical delay line 400, and the other two ends are connected together via optical fiber, thus forming the aforementioned loopback 612. Based on this structure, the fundamental mode signal, after the initial delay by the optical delay line 400, enters the beam splitter 611. The beam splitter 611 performs beam splitting on the fundamental mode signal to obtain two optical signals with equal intensity and phase. The two optical signals return to the beam splitter 611 via loop 612 in opposite directions. At this time, the light intensity and phase of the two optical signals are still equal. The beam splitter 611 becomes a beam combiner and combines the two optical signals. The combined optical signal returns to the delay line 400 along the original path for a second delay.

[0179] Based on the structure shown in Figures 12, 13a, or 13b, a reflective element can be used to multiplex the optical signals in two frequency-modulated optoelectronic circuits back and forth using the same optical delay line. However, this structure can also be extended to signal processing devices with three or more frequency-modulated optoelectronic circuits, so that the three or more frequency-modulated optoelectronic circuits share the same optical delay line 400 to transmit the optical signals in the three or more frequency-modulated optoelectronic circuits back and forth twice.

[0180] For example, taking the structure of the reflective element 600 shown in Figure 13a as an example, please refer to Figure 14, which shows a structural diagram of another possible signal processing device provided in Scheme 3. This structure can use the same optical delay line 400 to transmit optical signals in N+1 frequency-modulated photoelectric loops twice, where N is a positive integer greater than or equal to 2.

[0181] As shown in Figure 14, the signal processing device may include a first frequency-modulated photoelectric circuit 110 and N second frequency-modulated photoelectric circuits 210 to 2N0. The mode conversion element 300 includes a first optical transmission element 510, a first mode converter 310, a second mode converter 320, N second optical transmission elements 521 to 52N, N third mode converters 331 to 33N, and N fourth mode converters 341 to 34N. The reflection element 600 includes a first reflector 610 and N second reflectors 621 to 62N.

[0182] Please refer to Figure 15, which shows a partially enlarged structural view of each mode converter, each reflector, and optical delay line 400 in Figure 14. Combining Figures 14 and 15, for the first frequency modulation optoelectronic circuit 110, the first optical transmission element 510 is connected between the beam splitter 112, the left end of the first mode converter 310 (illustrated), and the mixer 114. The right end of the first mode converter 310 (illustrated) is connected to the first end a1 of the optical delay line 400. The left end of the second mode converter 320 (illustrated) is connected to the second end a2 of the optical delay line 400, and the right end of the second mode converter 320 (illustrated) is connected to the first reflector 610. For the N second frequency-modulated optoelectronic circuits 210 to 2N0, the N second optical transmission elements 521 to 52N are connected one-to-one between the N beam splitters 212 to 2N2, the N third mode converters 331 to 33N (as shown in the diagram on the left), and the N mixers 214 to 2N4. The right ends of the N third mode converters 331 to 33N are respectively coupled to the N first positions K of the optical delay line 400. 11 ~K 1N N first positions K 11 ~K 1N The optical delay line 400 is arranged sequentially between the first mode converter 310 and the first end a1 of the optical delay line 400, with the optical delay line 400 at N first positions K. 11 ~K 1N The cross-sectional dimensions are different. Similarly, the right ends of the N fourth mode converters 321-32N are respectively connected to N second reflectors 621-62N, and the left ends are respectively coupled to N second positions K. 21 ~K 2N N second positions K 21 ~K 2N The optical delay line 400 is arranged sequentially between the second mode converter 320 and the second end a2 of the optical delay line 400, with the optical delay line 400 at N second positions K. 21 ~K 2N Their cross-sectional dimensions are different.

[0183] Optionally, as shown in Figure 15, the optical delay line 400 has N first positions K 11 ~K 1N The cross-sectional size of the optical delay line 400 shows an increasing trend. That is, looking from left to right in Figure 15, the closer to the first end a1, the larger the cross-sectional size of the optical delay line 400, and the more optical signal modes it can accommodate. Similarly, the optical delay line 400 at N second positions K... 21 ~K 2N The cross-sectional size also shows an increasing trend. That is to say, in Figure 15, from right to left, the closer to the second end a2, the larger the cross-sectional size of the optical delay line 400, and the more optical signal modes the optical delay line 400 can accommodate.

[0184] Based on this structure and positional relationship, in the first frequency-modulated photoelectric circuit 110, the first optical signal S after being split by the beam-splitting element 112 is... 11 The light enters the first optical transmission element 510 and is transmitted by the first optical transmission element 510 to the first mode converter 310. The first mode converter 310 converts the first optical signal S into a signal. 11 The fundamental mode of a single-mode fiber or single-mode waveguide is converted to the fundamental mode of a multimode fiber or multimode waveguide and output to the optical delay line 400. In the second frequency-modulated optoelectronic circuit 210, the second optical signal S after splitting by the beam splitter 212... 21 The signal enters the second optical transmission element 521 and is transmitted by the second optical transmission element 521 to the third mode converter 331. The third mode converter 331 converts the second optical signal S into a signal that is transmitted to the second optical transmission element 521. 21 The fundamental mode of a single-mode fiber or waveguide is converted to the first-order mode of a multimode fiber or waveguide, and the first position K is achieved. 11 The input optical delay line is 400. In the second frequency-modulated optoelectronic circuit 220, the second optical signal S after splitting by the beam-splitting element 222... 22 The signal enters the second optical transmission element 522 and is transmitted by the second optical transmission element 522 to the third mode converter 332. The third mode converter 332 converts the second optical signal S into a signal. 22 The fundamental mode of a single-mode fiber or waveguide is converted to the second-order mode of a multimode fiber or waveguide, and at the first position K... 12 The incident light delay line is 400°. ... In the second frequency-modulated optoelectronic circuit 2N0, the second optical signal S after being split by the beam splitter 2N2 is... 2N The signal enters the second optical transmission element 52N and is transmitted by the second optical transmission element 52N to the third mode converter 33N. The third mode converter 33N converts the second optical signal S into a signal. 2N The fundamental mode of a single-mode fiber or waveguide is converted to the Nth-order mode of a multimode fiber or waveguide, and the K-order mode is obtained at the first position. 1N The optical delay line is 400°.

[0185] Based on this, N+1 different optical signals will be input into the optical delay line 400 on the same side. After being propagated in the same direction and delayed within the optical delay line 400, they will reach the second end a2 of the optical delay line 400. The Nth-order mode optical signal of the multimode fiber or multimode waveguide is located at position K in the second position. 2N The coupled optical delay line 400 enters the fourth mode converter 34N, where it is converted into the fundamental mode signal of a single-mode fiber or waveguide. The signal then enters the second reflector 62N, is reflected back to the fourth mode converter 34N, and is converted back into the Nth-order mode of a multimode fiber or waveguide. Finally, it is positioned at K... 2N Recouple the optical delay line 400. Similarly, the second-order mode optical signal of the multimode fiber or multimode waveguide is at the second position K.22 The coupled optical delay line 400 enters the fourth mode converter 342, where it is converted into the fundamental mode signal of a single-mode fiber or waveguide. The signal then enters the second reflector 622, is reflected back to the fourth mode converter 342, and is converted back into the second-order mode of a multimode fiber or waveguide. Finally, it is positioned at the second position K. 22 Recoupled into optical delay line 400. The first-order mode optical signal of the multimode fiber or multimode waveguide is at the second position K of optical delay line 400. 21 The coupled optical delay line 400 enters the fourth mode converter 341, where it is converted into the fundamental mode signal of a single-mode fiber or waveguide. The signal then enters the second reflector 621, is reflected back to the fourth mode converter 341, and is converted back into the first-order mode of a multimode fiber or waveguide. Finally, it is positioned at the second position K. 21 The optical delay line 400 is recoupled. The fundamental mode optical signal of the multimode fiber or multimode waveguide is directly transmitted to the second mode converter 320, converted into a single-mode fiber or single-mode waveguide optical signal by the second mode converter 320, and then enters the first reflector 610. The first reflector 610 reflects the signal back to the second mode converter 320, which converts it back into a multimode fiber or multimode waveguide fundamental mode signal and then enters the optical delay line 400.

[0186] Thus, after the initial delay in the optical delay line 400, the N+1 different optical signals are reflected back to the optical delay line 400 by their respective reflectors for a second delay, reaching the first end a1 of the optical delay line 400. The Nth-order mode optical signal of the multimode fiber or multimode waveguide is located at position K. 1N The coupled optical delay line 400 enters the third mode converter 32N, where it converts the signal into the fundamental mode of a single-mode fiber or waveguide. This fundamental mode then enters the second optical transmission element 52N, which transmits it to the mixer 2N4. There, it mixes the signal with the local oscillator signal from the calibration path in the second frequency-modulated optoelectronic circuit 2N0 to obtain the intermediate frequency signal in the second frequency-modulated optoelectronic circuit 2N0. Similarly, the second-order mode optical signal from the multimode fiber or waveguide is generated at position K. 12 The coupled optical delay line 400 enters the third mode converter 322, where it is converted into the fundamental mode signal of a single-mode fiber or single-mode waveguide. This signal then enters the second optical transmission element 522 and is transmitted to the mixer 224. There, it is mixed with the local oscillator signal from the calibration path in the second frequency-modulated optoelectronic circuit 220 to obtain the intermediate frequency signal in the second frequency-modulated optoelectronic circuit 220. The first-order mode optical signal of the multimode fiber or multimode waveguide is located at position K. 11The optical delay line 400 is coupled out and enters the third mode converter 321. The third mode converter 321 converts the signal into the fundamental mode of a single-mode fiber or single-mode waveguide, then it enters the second optical transmission element 521. The second optical transmission element 521 transmits the signal to the mixer 214, where it is mixed with the local oscillator signal of the calibration path in the second frequency-modulated optoelectronic circuit 210 to obtain the intermediate frequency (IF) signal in the second frequency-modulated optoelectronic circuit 210. Meanwhile, the fundamental mode optical signal of the multimode fiber or multimode waveguide directly enters the first mode converter 310. The first mode converter 310 converts the signal into the fundamental mode of a single-mode fiber or single-mode waveguide, then it enters the first optical transmission element 510. The first optical transmission element 510 transmits the signal to the mixer 114, where it is mixed with the local oscillator signal of the calibration path in the first frequency-modulated optoelectronic circuit 110 to obtain the IF signal in the first frequency-modulated optoelectronic circuit 110.

[0187] Based on the structure shown in Figure 14, the optical signals in the N+1 frequency-modulated optoelectronic circuits pass through the same optical delay line twice. Thus, the same optical delay line can be reused to achieve two delays for the optical signals in the N+1 frequency-modulated optoelectronic circuits. Compared to existing technologies, this not only saves N optical delay lines but also reduces the physical length of the optical delay lines by half, without reducing the delay time of the optical signals to be delayed. It maintains the original delay effect while reducing the size and cost of the optical delay lines, achieving a minimalist architecture and extremely low cost for the signal processing device. Furthermore, all the aforementioned components can be implemented on a chip; therefore, the above structure can also achieve chip-level integration for the reuse of optical delay lines.

[0188] Implementation Plan 4

[0189] Here, implementation scheme four corresponds to a scheme in which at least two optical signals are transmitted back and forth twice in the same optical delay line 400.

[0190] Please refer to Figure 16, which shows a schematic diagram of a signal processing device provided in Embodiment 4. Similar to Embodiment 3 above, the mode conversion element 300 also includes a first optical transmission element 510, a first mode converter 310, a second mode converter 320, a second optical transmission element 521, a third mode converter 331, and a fourth mode converter 341. The signal processing device includes reflective elements, such as a first reflector 610 and a second reflector 621. Except for the third mode converter 331 and the fourth mode converter 341, the structure, connection relationship with other components, and functions of the other components are the same as in Embodiment 3 above, and will not be repeated here.

[0191] Unlike the third embodiment described above, as shown in Figure 16, one end of the third mode converter 331 (the right end in the figure) is connected to the second end e of the second optical transmission element 521. 22The other end (left end in the diagram) is coupled to the second position K of the optical delay line 400. 21 The second position K 21 Located between the second mode converter 320 and the second end a2 of the optical delay line 400. One end of the fourth mode converter 341 (left end in the figure) is connected to the second reflector 621, and the other end (right end in the figure) is coupled to the first position K of the optical delay line 400. 11 First position K 11 Located between the first mode converter 310 and the first end a1 of the optical delay line 400. The second optical signal S after being split by the beam splitter 212. 21 The signal is output to the second optical transmission element 521, transmitted by the second optical transmission element 521 to the third mode converter 331, converted by the third mode converter 331 into a high-order mode signal of multimode fiber or multimode waveguide, and then output from the second position K. 21 Coupled into the optical delay line 400, after the propagation delay in the optical delay line 400, at the first position K 11 The coupled optical delay line 400 enters the fourth mode converter 341. The fourth mode converter 341 converts the delayed high-order mode signal into a fundamental mode signal of a single-mode fiber or single-mode waveguide and outputs it to the second reflector 621. This fundamental mode signal is reflected back to the fourth mode converter 341 by the second reflector 621, and then converted into a high-order mode signal of a multimode fiber or multimode waveguide by the fourth mode converter 341, and then output to the first position K. 11 After being recoupled into the optical delay line 400, and after the second propagation delay in the optical delay line 400, at the second position K of the optical delay line 400... 21 The signal is coupled out and enters the third mode converter 331. The third mode converter 331 converts the high-order mode signal after the second delay processing into the fundamental mode signal of the single-mode fiber or single-mode waveguide and outputs it to the second optical transmission element 521. The second optical transmission element 521 outputs it to the mixer 214 to participate in the mixing operation in the second frequency modulation optoelectronic circuit 210.

[0192] Based on the structure shown in Figure 16, optical signals from two frequency-modulated optoelectronic circuits can be transmitted in reverse using the same optical delay line, with each optical signal being transmitted twice back and forth within the same optical delay line. This structure can also be extended to signal processing devices with three or more frequency-modulated optoelectronic circuits, allowing the three or more frequency-modulated optoelectronic circuits to share the same optical delay line 400 to transmit optical signals from the three or more frequency-modulated optoelectronic circuits in reverse and forward directions.

[0193] For example, please refer to Figure 17, which shows a structural diagram of another possible signal processing device provided in Implementation Scheme 4. This structure can share the same optical delay line 400 to transmit optical signals in N+1 frequency-modulated optoelectronic loops in reverse and round trip, where N is a positive integer greater than or equal to 2.

[0194] Similar to implementation scheme 3, as shown in Figure 17, N+1 frequency-modulated optoelectronic circuits refer to one first frequency-modulated optoelectronic circuit 110 and N second frequency-modulated optoelectronic circuits 210 to 2N0. The first frequency-modulated optoelectronic circuit 110 corresponds to the first optical transmission element 510, the first mode converter 310, the second mode converter 320, and the first reflector 610. The N second frequency-modulated optoelectronic circuits 210 to 2N0 correspond to N first optical transmission elements 521 to 52N, N third mode converters 331 to 33N, N fourth mode converters 341 to 34N, and N second reflectors 621 to 62N.

[0195] Figure 18 shows a partially enlarged structural view of each mode converter, each reflector, and the optical delay line 400 in Figure 17. Combining Figure 18 and Figure 17, for the first frequency modulation optoelectronic circuit 110, the first optical transmission element 510 is connected between the beam splitter 112, the left end of the first mode converter 310 (shown in the figure), and the mixer 114. The right end of the first mode converter 310 (shown in the figure) is connected to the first end a1 of the optical delay line 400. The left end of the second mode converter 320 (shown in the figure) is connected to the second end a2 of the optical delay line 400, and the right end of the second mode converter 320 (shown in the figure) is connected to the first reflector 610. For the N second frequency-modulated optoelectronic circuits 210 to 2N0, the N second optical transmission elements 521 to 52N are connected one-to-one between the N beam splitters 212 to 2N2, the right end of the N third mode converters 331 to 33N (as shown in the diagram), and the N mixers 214 to 2N4. The left end of the N third mode converters 331 to 33N (as shown in the diagram) is coupled to the N second positions K of the optical delay line 400. 21 ~K 2N N second positions K 21 ~K 2N The optical delay line 400 is arranged sequentially between the second mode converter 320 and the second end a2 of the optical delay line 400, with the optical delay line 400 at N second positions K. 21 ~K 2N The cross-sectional dimensions are different. Similarly, the left ends of the N fourth mode converters 341-34N are respectively connected to N second reflectors 621-62N, and the right ends are respectively coupled to N first positions K of the optical delay line 400. 11 ~K 1N N first positions K 11 ~K 1N The optical delay line 400 is arranged sequentially between the first mode converter 310 and the first end a1 of the optical delay line 400, with the optical delay line 400 at N first positions K. 11 ~K 1N Their cross-sectional dimensions are different.

[0196] Optionally, as shown in Figure 18, the optical delay line 400 is at N second positions K 21 ~K2N The cross-sectional size of the optical delay line 400 shows an increasing trend. That is, looking from right to left in Figure 18, the closer to the second end a2, the larger the cross-sectional size of the optical delay line 400, and the more optical signal modes it can accommodate. Similarly, the optical delay line 400 at N first positions K... 11 ~K 1N The cross-sectional size also shows an increasing trend. Thus, in Figure 18, from left to right, the closer to the first end a1, the larger the cross-sectional size of the optical delay line 400, and the more optical signal modes the optical delay line 400 can accommodate.

[0197] Based on this structure and connection, in the first frequency-modulated photoelectric circuit 110, the first optical signal S after being split by the beam splitter 112 is... 11 The light enters the first optical transmission element 510 and is transmitted by the first optical transmission element 510 to the first mode converter 310. The first mode converter 310 converts the first optical signal S into a signal transducer. 11 The signal is converted from the fundamental mode of a single-mode fiber or waveguide to the fundamental mode of a multimode fiber or waveguide and output to the first end a1 of the optical delay line 400. It then propagates from left to right within the optical delay line 400 to the second end a2 and is transmitted to the second mode converter 320. The second mode converter 320 converts the initially delayed fundamental mode signal from the multimode fiber or waveguide to the fundamental mode of a single-mode fiber or waveguide and outputs it to the first reflector 610. The signal is then reflected back to the second mode converter 320, converted back to the fundamental mode of a multimode fiber or waveguide, and returns to the second end a2 of the optical delay line 400. It then propagates from left to right to the first end a1 of the optical delay line 400 and is transmitted to the first mode converter 310. The first mode converter 310 converts the fundamental mode signal after two delays from the fundamental mode of the multimode fiber or multimode waveguide to the fundamental mode of the single-mode fiber or single-mode waveguide, and outputs it to the first optical transmission element 510, which then transmits it to the mixer 114 in the first frequency modulation optoelectronic circuit 110.

[0198] In the second frequency-modulated photoelectric circuit 210, the second optical signal S after being split by the beam splitter 212 21 The signal enters the second optical transmission element 521 and is transmitted by the second optical transmission element 521 to the third mode converter 331. The third mode converter 331 converts the second optical signal S into a signal that is transmitted to the second optical transmission element 521. 21 The fundamental mode of a single-mode fiber or waveguide is converted to the first-order mode of a multimode fiber or waveguide, and at the second position K... 21 The input optical delay line is 400. In the second frequency-modulated optoelectronic circuit 220, the second optical signal S after splitting by the beam-splitting element 222... 22The signal enters the second optical transmission element 522 and is transmitted by the second optical transmission element 522 to the third mode converter 332. The third mode converter 332 converts the second optical signal S into a signal. 22 The fundamental mode of a single-mode fiber or waveguide is converted to the second-order mode of a multimode fiber or waveguide, and at the second position K... 22 The incident light delay line is 400°. ... In the second frequency-modulated optoelectronic circuit 2N0, the second optical signal S after being split by the beam splitter 2N2 is... 2N The signal enters the second optical transmission element 52N and is transmitted by the second optical transmission element 52N to the third mode converter 33N. The third mode converter 33N converts the second optical signal S into a signal. 2N The fundamental mode of a single-mode fiber or waveguide is converted to the Nth-order mode of a multimode fiber or waveguide, and at the second position K... 2N It is coupled into the optical delay line 400.

[0199] Furthermore, the N higher-order mode signals, after being delayed and propagated in the same direction from right to left in the optical delay line 400, arrive at the first end a1 of the optical delay line 400. The initial delayed signal of the Nth-order mode of the multimode fiber or multimode waveguide is located at the first position K of the optical delay line 400. 1N The signal is coupled out, converted into the fundamental mode signal of a single-mode fiber or single-mode waveguide by the fourth mode converter 34N, and then enters the second reflector 62N. It is reflected back to the fourth mode converter 34N, and then converted into the first delayed N-order mode signal of a multimode fiber or multimode waveguide by the fourth mode converter 34N. Finally, it is positioned at K... 1N Recoupled into optical delay line 400. Similarly, the first-order delayed signal of the second mode of the multimode fiber or multimode waveguide is at the first position K of optical delay line 400. 12 The signal is coupled out, converted into the fundamental mode signal of a single-mode fiber or single-mode waveguide by the fourth mode converter 342, and then enters the second reflector 622. It is reflected back to the fourth mode converter 342, where it is converted into the first delayed second-order mode signal of a multimode fiber or multimode waveguide. Finally, it is positioned at the first position K. 12 Recoupled into optical delay line 400. The first-order mode delay signal of the multimode fiber or multimode waveguide is at the first position K of optical delay line 400. 11 The signal is coupled out, converted into the fundamental mode signal of a single-mode fiber or waveguide by the fourth mode converter 341, and then enters the second reflector 621. It is reflected back to the fourth mode converter 341, where it is converted into the first-order delayed signal of the first mode of a multimode fiber or waveguide. Finally, it is positioned at the first position K. 11 Recouple the optical delay line 400.

[0200] Furthermore, the higher-order mode signals of the N modes, after the initial delay, are propagated in the same direction from left to right in the optical delay line 400 and reach the first end a2 of the optical delay line 400 after the delay. The second-order delayed signal of the Nth-order mode of the multimode fiber or multimode waveguide is located at the second position K of the optical delay line 400. 2N The signal is coupled out and converted into the fundamental mode signal of a single-mode fiber or waveguide by the third mode converter 33N, then enters the mixer 2N4 to participate in the mixing operation in the second frequency modulation optoelectronic circuit 2N0. Similarly, the second-order mode of the multimode fiber or waveguide, after a second delay, is at the second position K of the optical delay line 400. 22 The signal is coupled out and converted into the fundamental mode signal of a single-mode fiber or waveguide by the third mode converter 332, then enters the mixer 224 to participate in the mixing operation in the second frequency modulation optoelectronic circuit 220. The second-order delayed signal of the first mode of the multimode fiber or waveguide is at the second position K of the optical delay line 400. 21 The signal is coupled out and converted into the fundamental mode signal of a single-mode fiber or a single-mode waveguide by the third mode converter 331, and then enters the mixer 214 to participate in the mixing operation in the second frequency modulation optoelectronic circuit 210.

[0201] Using the structure shown in Figure 18, the optical signals in N+1 frequency-modulated photoelectric loops travel back and forth twice along the same optical delay line. Furthermore, the transmission direction of the optical signal in one of the frequency-modulated photoelectric loops is opposite to that of the other N frequency-modulated photoelectric loops. In this way, the same optical delay line can be reused to achieve a two-way delay of the optical signal. Compared to existing technologies, this not only saves N optical delay lines but also reduces the physical length of the optical delay lines by half, without reducing the delay time of the optical signal to be delayed. It maintains the original delay effect while reducing the size and cost of the optical delay lines, achieving a minimalist architecture and extremely low cost for the signal processing device. In addition, all the above components can be implemented on a chip, thus enabling chip-level integration and reuse of the optical delay line.

[0202] It should be noted that the designs in Implementation Scheme 1 above also apply to Implementation Schemes 2 through Implementation Schemes 4. For example, in any of Implementation Schemes 2 through Implementation Scheme 4, N first positions K 21 ~K 2N The cross-sectional dimensions and / or N second positions K 21 ~K 2NThe cross-sectional dimensions can increase sequentially in a diagonal line, gradually increase in a curved line, or increase in some areas in a diagonal line and in others in a curved line, or increase in some areas in a diagonal or curved line while others remain unchanged or decrease, etc. For example, in any of embodiments two to four, the first mode converter 310 and the second mode converter 320 can be adiabatic mode converters, and any one of the N third mode converters 331-33N and the N fourth mode converters 341-34N can be a directional coupler. Furthermore, in any of embodiments two to four, the N first positions K... 21 ~K 2N Any two adjacent positions and / or N second positions K 21 ~K 2N An adiabatic mode converter can also be set between any two adjacent positions. For example, in any of the embodiments two through four, the first frequency-modulated photoelectric circuit and N second frequency-modulated photoelectric circuits can share the same target measurement path, or partially share the same target measurement path, while the others have their own separate target measurement paths. These details can be directly referred to in embodiment one above, and will not be repeated here.

[0203] Furthermore, the above four implementation schemes are merely illustrative examples of four possible ways to achieve the transmission of two or more optical signals in the same optical delay line in the same direction or in the opposite direction using a mode conversion element. In actual signal processing devices, there may be other implementation schemes. Any scheme that can reuse one or more optical delay lines to transmit two or more optical signals in the same direction or in the opposite direction in different modes is within the scope of protection of this application, and this application does not make any specific limitations on it.

[0204] The above content introduces the specific implementation scheme of at least two frequency-modulated optoelectronic circuits sharing the same optical delay line. The following section will introduce the specific structure and function of each component and assembly in the above scheme to provide an exemplary implementation scheme.

[0205] 1. Target measurement route

[0206] In this application, the target measurement path refers to a path used for detecting a target. The target measurement path can send detection signals into the detection space and receive signals reflected back from the target in the detected space, and then detect relevant information about the target based on the signals.

[0207] For example, taking the target measurement path 113 in Figure 6 as an example, as shown in Figure 19a, the target measurement path 113 may include a beam splitter 1131, an optical transmission element 1132, a mixer 1133, a photodetector 1134, an amplifier 1135, an analog-to-digital converter 1136, and a processing element 1137. The optical transmission element 1132 has a first terminal (b) 51 ), second end (b) 52 ) and the third end (b 53 ), first end b 51 To the second end b 52 Second end b 52 To the third end b 53 It is unidirectional transmission. The input terminal of the beam splitter 1131 is connected to the third output terminal c of the beam splitter 112. 13 One output terminal of the beam splitter 1131 is connected to the first terminal b of the optical transmission element 1132. 51 The other output is connected to one input of mixer 1133. The second terminal b of optical transmission element 1132... 52 Towards the probe space, the third end b of the optical transmission element 1132 53 Connect to the other input terminal of mixer 1133. Mixer 1133, photodetector 1134, amplifier 1135, analog-to-digital converter 1136 and processing element 1137 are connected in series.

[0208] Based on the above structure and connection relationship, as shown in Figure 19a, in the target measurement path 113, the beam splitter 1131 can receive the third output terminal c of the beam splitter 112. 13 The output detection signal is split into a transmission signal and a target path local oscillator signal. The target path local oscillator signal is directly input to mixer 1133. The transmission signal originates from the first terminal b of optical transmission element 1132. 51 Input, from the second end b of the optical transmission element 1132 52 The output illuminates the target in the detection space, and is then reflected back to the second end b of the optical transmission element 1132 after being reflected by the target. 52 and from the third end b of the optical transmission element 1132 53The signal is output to mixer 1133 (referred to as the received signal or echo signal). Mixer 1133 mixes the input target path local oscillator signal and the received signal to obtain an intermediate frequency (IF) signal for target measurement. Optical detection element 1134 detects this IF signal and inputs it to amplifier 1135. After amplification by amplifier 1135, the signal is input to analog-to-digital converter 1136. Analog-to-digital converter 1136 performs analog-to-digital conversion on the input IF signal to obtain a digital signal, which is then input to processing element 1137. Processing element 1137 processes the input digital signal to obtain relevant target information.

[0209] For example, processing element 1137 can perform a Fast Fourier Transform (FFT) on the digital signal to extract the target's distance and motion state information. Processing element 1137 can also analyze the temporal variation trend of the frequency difference in the digital signal to obtain the change in the target's position within different time intervals, and thus calculate the target's velocity. Furthermore, processing element 1137 can output data such as the target object's distance and velocity, and further convert it into position information in three-dimensional space for subsequent scene modeling, obstacle recognition, or other application requirements.

[0210] Optionally, the target measurement paths in different frequency-modulated optoelectronic circuits can be separate or shared. For example, Figure 19a shows a scheme where two frequency-modulated optoelectronic circuits have different target measurement paths, and Figure 19b shows a scheme where two frequency-modulated optoelectronic circuits share the same target measurement path 113. In the case of sharing, the beam splitting element 1131 in the target measurement path 113 shown in Figure 19a can be replaced by a beam combining and splitting element 1138 (for example, it can be a beam combiner / splitter, or a combination of a beam combiner and a beam splitter, or a combination of other components, etc., without limitation). The beam combining and splitting element 1138 has two input terminals and two output terminals, one of which is connected to the third output terminal c of the beam splitting element 112 in the first frequency-modulated optoelectronic circuit 110. 13 The other input terminal is connected to the third output terminal i of the beam splitter 212 in the second frequency modulation photoelectric circuit 210. 13 One output terminal is connected to the first terminal b of the optical transmission element 1132. 51 The other output is connected to one input of mixer 1133.

[0211] Based on the structure and connection relationship shown in Figure 19b, the beam combiner / splitter 1138 can receive the detection signal split by the beam splitter 112 in the first frequency-modulated photoelectric circuit 110 and the detection signal split by the beam splitter 212 in the second frequency-modulated photoelectric circuit 210 through its two input terminals. The beam combiner / splitter 1138 combines these two detection signals into one signal, and then splits them into a transmission signal and a target path local oscillator signal. The transmission signal is sent to the detection space to detect the target, while the target path local oscillator signal is input to the mixer 1133 to wait for mixing with the returned echo signal. In this way, by sharing a single target measurement path, the detection signals after splitting the optical signals modulated by the two frequency-modulated photoelectric circuits can be combined into one signal and used to measure the target together. This not only saves the number of target measurement paths that need to be set up, but also saves the cost and space of components, and increases the power of the detection signal for measuring the target.

[0212] 2. Light source

[0213] Alternatively, the light source can be any device capable of emitting light, such as a laser, including but not limited to: vertical cavity surface emitting laser (VCSEL), edge emitting laser (EEL), diode pumped solid state laser (DPSS), or fiber laser.

[0214] In one example, the light source can emit a frequency-modulated continuous wave. In other words, the signal processing device can be a component of the FMCWLiDAR.

[0215] 3. Spectrometer

[0216] Optionally, the beam splitting element can be any device or combination of devices with beam splitting function, such as a beam splitter, a beam combiner, a combination of beam splitters, or a combination of beam splitters and beam combiners.

[0217] For example, taking the beam splitter 112 in Figure 9 as an example, please refer to Figure 20a. The beam splitter 112 may specifically include a first beam splitter 1121 and a second beam splitter 1122. The input terminal of the first beam splitter 1121 corresponds to the input terminal of the beam splitter 112, that is, it is connected to the output terminal of the light source 111. The first output terminal (t) of the first beam splitter 1121... 11 The input terminal of the second beam splitter 1122 is connected to the second output terminal of the first beam splitter 1121. 12 The third output terminal c of the corresponding beam splitter 112 13 The first output terminal (t) of the second beam splitter 1122 21The first output terminal c of the corresponding beam splitter 112 11 The second output terminal (t) of the second beam splitter 1122 22 The second output terminal c of the corresponding beam splitter 112 12 Here, "two ends corresponding" means that the two ends are the same end, or the two ends are connected by a line. For example, the second output terminal t of the first beam splitter 1121 12 The third output terminal c of the corresponding beam splitter 112 13 This refers to the second output terminal t of the first beam splitter 1121. 12 That is, the third output terminal c of the beam splitter 112. 13 Or the second output terminal t of the first beam splitter 1121 12 The third output terminal c of the beam splitter 112 is connected via optical fiber. 13 .

[0218] Based on the above structure and connection, the optical signal S1 output by the light source 111 enters the first beam splitter 1121. The first beam splitter 1121 performs beam splitting processing on the optical signal S1 to obtain the detection signal and the intermediate optical signal S. 10 The first beam splitter 1121 outputs through its second output terminal t 12 The output detection signal is sent to the target measurement path 113 to participate in the target measurement. The first beam splitter 1121 also outputs a detection signal through its first output terminal t. 11 Output intermediate optical signal S 10 This makes the intermediate optical signal S 10 The signal enters the second beam splitter 1122. The second beam splitter 1122 splits the intermediate optical signal S... 10 The optical signal is split to obtain the calibration path local oscillator signal and the first optical signal S. 11 The second beam splitter 1122 outputs through its second output terminal t 22 The output calibration path local oscillator signal is directly fed into mixer 114. The second beam splitter 1122 also outputs the signal through its first output terminal t. 21 Output the first optical signal S 11 This makes the first optical signal S 11 After passing through the first mode converter 310, the optical delay line 400 and the second mode converter 320 in sequence, the signal enters the mixer 114.

[0219] It should be noted that the above beam splitters can be any type of beam splitter, including but not limited to: wavelength beam splitters, power beam splitters, resonant beam splitters, and other types of beam splitters, etc., without specific limitations here.

[0220] 4. Mode conversion element

[0221] Here, the mode conversion element may include the aforementioned first mode converter, second mode converter, third mode converter and fourth mode converter. The first mode converter and second mode converter may be adiabatic mode converters, the third mode converter and fourth mode converter may be directional couplers, or other components or combinations, as long as they can realize the function of mode converter.

[0222] 5. Optical Delay Line

[0223] Optionally, an optical delay line can be a component capable of delaying the transmission of optical signals, such as, but not limited to, fiber optic delay lines or integrated waveguide delay lines. Fiber optic delay lines utilize the propagation of optical signals within optical fibers to achieve signal delay and typically have a relatively long length. Integrated waveguide delay lines are waveguide devices fabricated on semiconductor chips. Their working principle involves controlling the propagation path length of electromagnetic waves in a dielectric waveguide, silicon, or other materials to achieve signal delay. The semiconductor materials used in integrated waveguide delay lines can be, for example, silicon (Si) or silicon nitride (SiN), and they transmit optical signals internally. Integrated waveguide delay lines offer numerous advantages, including, but not limited to, high integration density, good programmability, high delay accuracy, ease of integration with other circuits, and smaller size.

[0224] 6. Mixer

[0225] In a frequency modulation optoelectronic circuit, the mixer can perform frequency mixing on the input signal and output an intermediate frequency signal.

[0226] Optionally, the mixer can be any type of optical mixer, including but not limited to a 180° optical mixer or a 90° optical mixer. For example, taking the mixer 114 in Figure 9 above as an example, as shown in Figure 20a, mixer 114 can be a 180° optical mixer, which can process the local oscillator signal of the calibration path and the first optical signal S after delay processing in the first frequency modulation optoelectronic circuit 110. 11 Coherent mixing is performed so that the relative phase difference between the two output signals is 0° and 180°, respectively. For example, in another example, as shown in Figure 20b, mixer 114 can be a 90° optical mixer with four outputs, which can process the local oscillator signal of the calibration path and the first optical signal S after delay processing in the first frequency-modulated optoelectronic circuit 110. 11 Perform coherent mixing to make the relative phase differences between the four outputs 0°, 90°, 180°, and 270°, respectively. And so on, not listed here.

[0227] 7. Optical detection element

[0228] A photodetector, also known as a photoreceiver, is an electronic device used to detect optical signals and convert them into electrical signals. Photodetectors are typically located after a mixer, thus enabling them to detect the intermediate frequency (IF) signal output from the mixer and convert it into an electrical signal. Optionally, examples of photodetectors include, but are not limited to: phototubes, photomultiplier tubes, photodiodes (PDs), avalanche photodiodes (APDs), and single-photon avalanche diodes (SPADs).

[0229] Taking a photodetector (PD) as an example, the photodetector element can include at least one PD, and the number of at least one PD can be the same as the number of output terminals of the mixer placed in front of it. For example, taking the photodetector element 115 in Figure 9 above as an example, and referring to Figures 9 and 20a, when the mixer 114 is a 180° optical mixer, the photodetector element 115 can specifically include two PDs, namely PD11 and PD12. The input terminals of PD11 and PD12 are both connected to the output terminals of the 180° optical mixer, and the output terminals of PD11 and PD12 are connected to the input terminals of amplifier 118. PD11 and PD12 can be used to detect signals with a relative phase difference of 0° and 180° output from the 180° optical mixer, convert them into electrical signals, and then combine them on a single line for transmission to amplifier 118. For example, referring to Figures 9 and 20b, when mixer 114 is a 90° optical mixer, the optical detection element 115 may specifically include four photodetectors (PDs), namely PD11a, PD11b, PD12a, and PD12b. The input terminals of the four PDs are respectively connected to the four output terminals of the 90° optical mixer, and the output terminals of every two PDs are connected to the input terminal of an amplifier. The four PDs can be used to detect signals with relative phase differences of 0°, 90°, 180°, and 270° output from the four output terminals of the 90° optical mixer, convert them into electrical signals, and then combine them in pairs before transmitting them to the subsequent amplifier.

[0230] 8. Amplifier

[0231] Optionally, the amplifier can be a component or combination of components with signal amplification function. For example, it can include a trans-impedance amplifier (TIA). A TIA can amplify the input signal with a certain intensity of low noise, that is, amplify the useful signal in the input signal while suppressing the amplification of noise signals, so as to improve the optical signal-to-noise ratio (OSNR).

[0232] Taking a TIA as an example, an amplifier may include at least one TIA. The number of TIAs can be related to the number of photodetectors (PDs) contained in the photodetector element positioned in front of it, for example, it can be half the number of PDs. For example, taking amplifier 118 in Figure 9 as an example, combined with Figures 9 and 20a, when the photodetector element 115 includes two PDs, namely PD11 and PD12, amplifier 118 may include one TIA, namely TIA 1180. The output terminals of PD11 and PD12 are combined and connected to the input terminal of TIA 1180. Therefore, the two intermediate frequency signals detected by PD11 and PD12 are combined into one and sent to TIA 1180. TIA 1180 can perform low-noise amplification on the combined intermediate frequency signal Z1 with a certain intensity. For example, referring to Figures 9 and 20b, when the photodetector 115 includes four photodetectors (PDs), namely PD11a, PD11b, PD12a, and PD12b, the amplifier 118 can include two intermediate frequency amplifiers (TIAs), namely TIA 1181 and TIA 1182. The outputs of PD11a and PD11b are combined and connected to the input of TIA 1181, and the outputs of PD12a and PD12b are combined and connected to the input of TIA 1182. Therefore, the two intermediate frequency signals detected by PD11a and PD11b are combined into one signal and sent to TIA 1181 (referred to as the first intermediate frequency signal Z). 11 The two intermediate frequency signals detected by PD12a and PD12b are combined into one signal and sent to TIA 1182 (referred to as the second intermediate frequency signal Z). 12 TIA 1181 and TIA 1182 respectively process the first intermediate frequency signal Z... 11 Second intermediate frequency signal Z 12 Perform low-noise amplification at a certain intensity.

[0233] 9. Analog-to-digital converter

[0234] Analog-to-digital converters can sample received analog signals that are continuous in time and amplitude, and convert them into digital signals that are discrete in time and amplitude, thereby simplifying the software processing operations of subsequent processing components.

[0235] Optionally, the analog-to-digital conversion element may include at least one analog-to-digital converter (ADC), and the number of at least one ADC may be the same as the number of TIAs contained in the amplifier preceding it. For example, taking the analog-to-digital conversion element 119 in Figure 9 as an example, in conjunction with Figures 9 and 20a, when the amplifier 118 includes only one TIA, namely TIA 1180, the analog-to-digital conversion element 119 may include only one ADC, namely ADC 1190. The input terminal of ADC 1190 is connected to the output terminal of TIA 1180 and is used to perform analog-to-digital conversion on the amplified intermediate frequency signal Z1 output by TIA 1180 to obtain a digital signal. For example, referring to Figures 9 and 20b, when amplifier 118 includes two TIAs, namely TIA 1181 and TIA 1182, analog-to-digital converter element 119 can also include two ADCs, namely ADC 1191 and ADC 1192. The input terminal of ADC 1191 is connected to the output terminal of TIA 1181, and the input terminal of ADC 1192 is connected to the output terminal of TIA 1182. The output terminals of ADC 1191 and ADC 1192 are connected together to the input terminal of processing element 116. ADC 1191 is used to process the amplified first intermediate frequency signal Z output from TIA 1181. 11 Analog-to-digital conversion is performed to obtain the first digital signal. The ADC 1192 is used to amplify the second intermediate frequency signal Z output from the TIA 1182. 12 An analog-to-digital conversion is performed to obtain a second digital signal. The first and second digital signals are then input together to the processing element 116.

[0236] 10. Processing Components

[0237] A processing element refers to a device with signal processing capabilities, such as a digital signal processor (DSP). Taking the processing element 116 in Figure 9 as an example, as shown in Figure 20a or Figure 20b, the processing element 116 may specifically include a DSP 1160. The DSP 1160 can process one or more digital signals output by the analog-to-digital converter 119 to obtain a feedback signal P1, and input the feedback signal P1 into the drive circuit 117.

[0238] The feedback signal can be used to calibrate the linearity between the modulation signal output from the driver circuit to the light source and the optical signal output from the light source; this is referred to as nonlinear calibration. There are various ways to achieve nonlinear calibration, including but not limited to frequency sweep monitoring and frequency modulation signal pre-distortion. Frequency sweep monitoring involves calculating the frequency sweep curve by monitoring changes in the modulation signal and determining whether the curve is linear. If it is not linear, it is calibrated to be linear. Frequency modulation signal pre-distortion refers to pre-compensating for modulation signals that will produce nonlinearity, ensuring that the compensated modulation signal is not distorted, i.e., maintaining linearity. Of course, other nonlinear calibration methods are possible, but specific limitations are not discussed here.

[0239] 11. Drive circuit

[0240] In each frequency-modulated photoelectric circuit, the driving circuit can generate a modulation signal based on the feedback signal output by the processing element, and input the modulation signal into the light source. The modulation signal is used to drive the light source to output a light signal whose frequency changes linearly with time, such as a light signal whose frequency changes linearly with time in the form of a triangular wave or a sawtooth wave. In some cases, the driving circuit also needs to be responsible for timing control functions, such as controlling the time window for the light source to emit light signals, and synchronizing with the receiving end (i.e., the receiving operation of the target measurement path) in order to accurately demodulate the information in the echo signal (i.e., the received signal).

[0241] It should be noted that Figures 20a and 20b above are only examples of the components in the calibration path of the first frequency-modulated photoelectric circuit 110 (referring to the path containing the beam splitter 112, the first mode converter 310, the optical delay line 400, the second mode converter 320, the mixer 114, the photodetector 115, the amplifier 118, the analog-to-digital converter 119, and the processing element 116). However, the relevant content of these components also applies to the target measurement path 113 of the first frequency-modulated photoelectric circuit 110 (referring to the beam splitter 1131 shown in Figure 19a or the beam combiner / splitter 1138 shown in Figure 19b). The calibration path in the second frequency-modulated optoelectronic circuit 210 (which includes the path containing the transmission element 1132, mixer 1133, photodetector 1134, amplifier 1135, analog-to-digital converter 1136, and processing element 1137), the target measurement path 213 in the second frequency-modulated optoelectronic circuit 210, and other calibration and target measurement paths in the second frequency-modulated optoelectronic circuit.

[0242] Furthermore, within the same first frequency-modulated photoelectric circuit or the same second frequency-modulated photoelectric circuit, the mixer in the target measurement path and the mixer in the calibration path can be of the same type or different types. Similarly, within different first frequency-modulated photoelectric circuits or different second frequency-modulated photoelectric circuits, the mixer in the calibration path can be of the same type or different types, and the mixer in the target measurement path can also be of the same type or different types. For example, the following examples illustrate this:

[0243] Referring to Figures 19a, 20a, and 20b above, when the optical signals in the first frequency-modulated optoelectronic circuit 110 and the second frequency-modulated optoelectronic circuit 210 are transmitted in opposite directions along the same optical delay line 400, the beam splitting element 112 in the first frequency-modulated optoelectronic circuit 110 includes a first beam splitter 1121 and a second beam splitter 1122, the mixer 114 is a 180° optical mixer, the photodetector element 115 includes PD11 and PD12, the amplifier 118 is a TIA 1180, the analog-to-digital converter element 119 is an ADC 1190, and the processing element 116 is a DSP 1160. On the target measurement path 113, the beam splitting element 1131 is a third beam splitter 11310, the mixer 1133 is a 180° optical mixer, the photodetector element 1134 includes PD13 and PD14, the amplifier 1135 is a TIA 11350, and the analog-to-digital converter element 1136 is an ADC. When the processing element 11360 and the processing element 1137 are DSP 11370, the beam splitting element 212 in the second frequency modulation optoelectronic circuit 210 includes a first beam splitter 2121 and a second beam splitter 2122, the mixer 214 is a 90° optical mixer, the photodetector element 215 includes PD21a, PD21b, PD22a and PD22b, the amplifier 218 includes TIA 2181 and TIA 2182, the analog-to-digital converter element 219 includes ADC 2191 and ADC 2192, the processing element 216 is DSP 2160, the beam splitting element on the target measurement path 213 is a fourth beam splitter 21310, the mixer is a 180° optical mixer, the photodetector element includes PD23 and PD24, the amplifier is TIA 21350, the analog-to-digital converter element is ADC 21360, and the processing element is DSP 21370, the structure of the signal processing device is shown in Figure 21a.

[0244] Referring to Figures 19a, 20a, and 20b above, when the optical signals in the first frequency-modulated optoelectronic circuit 110 and the second frequency-modulated optoelectronic circuit 210 are transmitted in opposite directions along the same optical delay line 400, the beam splitting element 112 in the first frequency-modulated optoelectronic circuit 110 includes a first beam splitter 1121 and a second beam splitter 1122, the mixer 114 is a 180° optical mixer, the photodetector element 115 includes PD11 and PD12, the amplifier 118 is a TIA 1180, the analog-to-digital converter element 119 is an ADC 1190, and the processing element 116 is a DSP 1160. On the target measurement path 113, the beam splitting element 1131 is a third beam splitter 11310, the mixer 1133 is a 90° optical mixer, the photodetector element 1134 includes PD13a, PD13b, PD14a, and PD14b, and the amplifier 1135 includes TIA 11351 and TIA 11352. When the signal processing device is configured as follows: 11352, analog-to-digital conversion element 1136 includes ADC 11361 and ADC 11362, processing element 1137 is DSP 11370, beam splitting element 212 in the second frequency modulation optoelectronic circuit 210 includes first beam splitter 2121 and second beam splitter 2122, mixer 214 is 180° optical mixer, photodetector 215 includes PD21 and PD22, amplifier 218 is TIA 2180, analog-to-digital conversion element 219 is ADC 2190, processing element 216 is DSP 2160, and beam splitting element on target measurement path 213 is fourth beam splitter 21310, mixer is 180° optical mixer, photodetector includes PD23 and PD24, amplifier is TIA 21350, analog-to-digital conversion element is ADC 21360, and processing element is DSP 21370, the structure of the signal processing device is shown in Figure 21b.

[0245] Referring to Figures 6, 19b, 20a, and 20b above, when the optical signals in the first frequency-modulated photoelectric circuit 110 and the second frequency-modulated photoelectric circuit 210 are transmitted in the same direction along the same optical delay line 400, the first frequency-modulated photoelectric circuit 110 and the second frequency-modulated photoelectric circuit 210 share the same target measurement path 113. The beam splitting element 112 in the first frequency-modulated photoelectric circuit 110 includes a first beam splitter 1121 and a second beam splitter 1122; the mixer 114 is a 90° optical mixer; the photodetector element 115 includes PD11a, PD11b, PD12a, and PD12b; the amplifier 118 includes TIA 1181 and TIA 1182; the analog-to-digital converter element 119 includes ADC 1191 and ADC 1192; and the processing element 116 is a DSP. 1160, the beam splitting element 212 in the second frequency modulation optoelectronic circuit 210 includes a first beam splitter 2121 and a second beam splitter 2122; the mixer 214 is a 90° optical mixer; the photodetector element 215 includes PD21a, PD21b, PD22a and PD22b; the amplifier 218 includes TIA 2181 and TIA 2182; the analog-to-digital converter element 219 includes ADC 2191 and ADC 2192; and the processing element 216 is a DSP 2160. The beam combining and splitting element 1138 on the target measurement path 113 is a beam combiner / splitter 11380; the mixer 1133 is a 90° optical mixer; the photodetector element 1134 includes PD13a, PD13b, PD14a and PD14b; the amplifier 1135 includes TIA 11351 and TIA 11352; and the analog-to-digital converter element 1136 includes an ADC. When 11361, ADC 11362, and processing element 1137 are DSP 11370, the structure of the signal processing device is shown in Figure 21c.

[0246] Referring to Figures 6, 19b, 20a, and 20b above, when the optical signals in the first frequency-modulated photoelectric circuit 110 and the second frequency-modulated photoelectric circuit 210 are transmitted in the same direction along the same optical delay line 400, the first frequency-modulated photoelectric circuit 110 and the second frequency-modulated photoelectric circuit 210 share the same target measurement path 113. The beam splitting element 112 in the first frequency-modulated photoelectric circuit 110 includes a first beam splitter 1121 and a second beam splitter 1122; the mixer 114 is a 90° optical mixer; the photodetector element 115 includes PD11a, PD11b, PD12a, and PD12b; the amplifier 118 includes TIA 1181 and TIA 1182; the analog-to-digital converter element 119 includes ADC 1191 and ADC 1192; and the processing element 116 is a DSP. 1160. In the second frequency modulation optoelectronic circuit 210, the beam splitting element 212 includes a first beam splitter 2121 and a second beam splitter 2122, the mixer 214 is a 180° optical mixer, the photodetector element 215 includes PD21 and PD22, the amplifier 218 is a TIA 2180, the analog-to-digital converter element 219 is an ADC 2190, and the processing element 216 is a DSP 2160. In the target measurement path 113, the beam combining and splitting element 1138 is a beam combiner and splitter 11380, the mixer 1133 is a 180° optical mixer, the photodetector element 1134 includes PD13 and PD14, the amplifier 1135 is a TIA 11350, the analog-to-digital converter element 1136 is an ADC 11360, and the processing element 1137 is a DSP 11370. The specific structure of the signal processing device can be shown in Figure 21d.

[0247] Understandably, other similar related structures can be deduced from the above content, and will not be listed one by one here.

[0248] Based on the structure and functional principle of the signal processing device described above, this application can also provide a detection device, as shown in FIG22. The detection device 2200 includes a signal processing device 2210, which can be the signal processing device in any of the above embodiments, such as the signal processing device described in any of FIG4 to FIG21d.

[0249] Alternatively, the detection device 2200 can be a lidar, such as an FMCW LiDAR.

[0250] Optionally, as shown in Figure 22 above, the detection device 2200 may further include a window 2220, which is used to protect the internal signal processing device 2210 and can transmit the light signal emitted by the signal processing device 2210.

[0251] It should be noted that the detection device architecture shown in Figure 22 is only an example. In other examples, the detection device may include more, fewer, or different structures, and each structure may include more, fewer, or different components. This application does not make any specific limitations in this regard.

[0252] Based on the structure and functional principles of the detection device described above, this application can also provide a terminal device, as shown in Figure 23. This terminal device 2300 may include the signal processing device described above, or it may include a detection device 2310. The detection device 2310 may be a detection device from any of the above embodiments, such as the detection device 2200 in Figure 22.

[0253] Optionally, as shown in Figure 23 above, the terminal device 2300 may further include a processor 2320, which is used to call programs or instructions to control the operation of the detection device 2310. Furthermore, the processor 2320 may also receive target-related information from the detection device 2310. When the terminal device 2300 is a vehicle, the processor 2320 may also perform vehicle path planning, braking, or starting based on this acquired information. For example, the vehicle's position can be determined using latitude and longitude, or the vehicle's direction of travel and destination in the future can be determined using speed and orientation, or the number and density of obstacles around the vehicle can be determined using the distance to surrounding objects.

[0254] Furthermore, optionally, the terminal device 2300 may also include a memory 2330 for storing programs or instructions. Of course, the terminal device 2300 may also include other devices, such as wireless communication devices.

[0255] Processor 2320 may include one or more processing units. For example, processor 2320 may include an application processor (AP), an image signal processor (ISP), a controller, a DSP, or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. Different processing units may be independent devices or integrated into one or more processors.

[0256] The memory 2330 includes, but is not limited to, random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, portable hard disks, CD-ROMs, or any other form of storage medium known in the art. Exemplarily, the storage medium is coupled to a processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can reside within an ASIC.

[0257] For example, the terminal device 2300 may be a vehicle (e.g., unmanned vehicle, intelligent vehicle, electric vehicle, or digital car), robot, surveying equipment, drone, smart home device (e.g., television, robot vacuum cleaner, smart lamp, audio system, smart lighting system, electrical control system, home background music, home theater system, intercom system, or video surveillance), smart manufacturing equipment (e.g., industrial equipment), smart transportation equipment (e.g., AGV, unmanned transport vehicle, or truck), or smart terminal (mobile phone, computer, tablet, PDA, desktop computer, headphones, audio equipment, wearable device, in-vehicle device, virtual reality device, augmented reality device, etc.).

[0258] It is understandable that, unless otherwise specified or logically conflicting, the terminology and / or descriptions of the various implementation schemes described above are consistent and can be referenced from each other. The technical features of different implementation schemes can be combined to form new implementation schemes based on their inherent logical relationships.

[0259] Furthermore, the above implementation schemes are merely examples of FMCW LiDAR to illustrate the internal structure of the signal processing device. It should be understood that the aforementioned signal processing device can also be applied to other applications requiring linear frequency modulation. For instance, in other scenarios, the above signal processing device can also be applied to optical frequency domain reflectometry (OFDR) systems. The structure of an OFDR system is similar to that of an FMCW LiDAR, except that the devices on its target measurement path are connected via optical fibers, while the calibration path is the same as that of an FMCW LiDAR. In this case, the structure of the above signal processing device can also be used to achieve the multiplexing of delay elements (such as optical delay lines). In addition, with the development of detection technology, the signal processing device structure provided in this application is also applicable to the same technical problems, and this application does not specifically limit its application in this regard.

[0260] In this application, "at least one" means one or more, and "more than one" means two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. In the textual description of this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0261] Additionally, in this application, the terms "optionally" or "exemplary" are used to indicate that they are examples, illustrations, or descriptions. Any embodiment or design described as "optional" or "exemplary" in this application should not be construed as being more preferred or advantageous than other embodiments or design options. Alternatively, it can be understood that the use of the terms "exemplary" or "optional" is intended to present concepts in a specific manner and does not constitute a limitation of this application.

[0262] It is understood that the various numerical designations used in this application are merely for descriptive convenience and are not intended to limit the scope of the embodiments of this application. The order of the process numbers described above does not imply the order of execution; the execution order of each process should be determined by its function and inherent logic. Terms such as "first," "second," and "third," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as including a series of steps or units. A method, system, product, or device is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or devices.

Claims

A signal processing device characterized by comprising: include: First frequency-modulated photoelectric circuit and second frequency-modulated photoelectric circuit; Each of the first and second frequency-modulated optoelectronic circuits includes a light source, a beam splitter, a mode conversion element, an optical delay line, and a mixer. The first frequency-modulated optoelectronic circuit and the second frequency-modulated optoelectronic circuit share the mode conversion element and the optical delay line, and the optical delay line supports optical signal transmission in at least two modes. The mode conversion element is used to receive a first optical signal split by a beam splitter in the first frequency-modulated optoelectronic circuit and a second optical signal split by a beam splitter in the second frequency-modulated optoelectronic circuit, output the first optical signal and the second optical signal to the optical delay line in different modes, output the delayed first optical signal to the mixer in the first frequency-modulated optoelectronic circuit in the original mode of the first frequency-modulated optoelectronic circuit, and output the delayed second optical signal to the mixer in the second frequency-modulated optoelectronic circuit in the original mode of the second frequency-modulated optoelectronic circuit. The apparatus of claim 1, wherein The mode conversion element includes a first mode converter and a second mode converter. The first mode converter is connected between the beam splitter of the first frequency-modulated optoelectronic circuit and the first end of the optical delay line, and the second mode converter is connected between the mixer of the first frequency-modulated optoelectronic circuit and the second end of the optical delay line. The first mode converter is used to convert the first optical signal into the fundamental mode signal in the optical delay line and output it to the optical delay line; The second mode converter is used to convert the fundamental mode signal after the delay processing of the optical delay line into the first optical signal after the delay processing in the first frequency modulation optoelectronic circuit, and output it to the mixer in the first frequency modulation optoelectronic circuit. The apparatus of claim 2, wherein The mode conversion element further includes a third mode converter and a fourth mode converter; one end of the third mode converter is connected to the beam splitter of the second frequency-modulated optoelectronic circuit, and the other end is coupled to the first position of the optical delay line, the first position being located between the first mode converter and the first end of the optical delay line; one end of the fourth mode converter is connected to the mixer of the second frequency-modulated optoelectronic circuit, and the other end is coupled to the second position of the optical delay line, the second position being located between the second mode converter and the second end of the optical delay line; The third mode converter is used to convert the second optical signal into a higher-order mode signal in the optical delay line and couple it into the optical delay line at the first position. The fourth mode converter is used to convert the high-order mode signal after the delay processing of the optical delay line into the second optical signal after the delay processing in the second frequency modulation optoelectronic circuit, and couple it out to the mixer in the second frequency modulation optoelectronic circuit at the second position. The apparatus of claim 2, wherein The mode conversion element further includes a third mode converter and a fourth mode converter; one end of the third mode converter is connected to the beam splitter of the second frequency-modulated optoelectronic circuit, and the other end is coupled to the second position of the optical delay line, the second position being located between the second mode converter and the second end of the optical delay line; one end of the fourth mode converter is connected to the mixer of the second frequency-modulated optoelectronic circuit, and the other end is coupled to the first position of the optical delay line, the first position being located between the first mode converter and the first end of the optical delay line; The third mode converter is used to convert the second optical signal into a higher-order mode signal in the optical delay line and couple it into the optical delay line at the second position. The fourth mode converter is used to convert the high-order mode signal after the delay processing of the optical delay line into the second optical signal after the delay processing in the second frequency modulation optoelectronic circuit, and couple it out to the mixer in the second frequency modulation optoelectronic circuit at the first position. The apparatus of claim 1, wherein The mode conversion element includes a first optical transmission element, a first mode converter, and a reflection element. The first optical transmission element is connected between the beam splitter of the first frequency-modulated optoelectronic circuit, the mixer in the first frequency-modulated optoelectronic circuit, and the first end of the first mode converter. The second end of the first mode converter is connected to the first end of the optical delay line. The first optical transmission element is used to transmit a first optical signal from a beam splitter in the first frequency-modulated optoelectronic circuit to the first mode converter, and to transmit a delayed signal from the first mode converter to a mixer in the first frequency-modulated optoelectronic circuit. The first mode converter is used to convert the first optical signal from the first optical transmission element into the fundamental mode signal in the optical delay line and output it to the optical delay line, and to convert the fundamental mode signal after two delay processing by the optical delay line into the delayed signal in the first frequency-modulated optoelectronic circuit and output it to the first optical transmission element. The reflective element is used to reflect the fundamental mode signal, after the initial delay by the optical delay line, back to the optical delay line. The apparatus of claim 5, wherein The reflective element includes a second mode converter and a first reflector, wherein the second mode converter is connected between the second end of the optical delay line and the first reflector; The second mode converter is used to convert the fundamental mode signal after the initial delay of the optical delay line into the initial delayed signal in the first frequency-modulated optoelectronic circuit and output it to the first reflector, and to convert the initial delayed signal reflected back by the first reflector into the fundamental mode signal in the optical delay line and output it to the optical delay line. The apparatus of claim 5 or 6, wherein The mode conversion element further includes a second optical transmission element and a third mode converter. The second optical transmission element is connected between the beam splitter of the second frequency modulation optoelectronic circuit, the mixer in the second frequency modulation optoelectronic circuit, and the first end of the third mode converter. The second end of the third mode converter is coupled to the first position of the optical delay line. The first position is located between the first mode converter and the first end of the optical delay line. The second optical transmission element is used to transmit the second optical signal from the beam splitter in the second frequency-modulated optoelectronic circuit to the third mode converter, and to transmit the delayed signal from the third mode converter to the mixer in the second frequency-modulated optoelectronic circuit. The third mode converter is used to convert the second optical signal from the second optical transmission element into a higher-order mode signal in the optical delay line and couple it into the optical delay line at the first position, and to convert the higher-order mode signal after two delay processing by the optical delay line into a delayed signal in the second frequency-modulated optoelectronic circuit and couple it out to the second optical transmission element at the first position. The reflective element is also used to reflect the higher-order mode signal after the initial delay of the optical delay line back to the optical delay line. The apparatus of claim 7, wherein The reflective element includes a fourth mode converter and a second reflector. One end of the fourth mode converter is connected to the second reflector, and the other end is coupled to a second position of the optical delay line. The second position is located between the second mode converter and the second end of the optical delay line. The fourth mode converter is used to convert the high-order mode signal after the initial delay of the optical delay line into the initial delayed signal in the second frequency-modulated optoelectronic circuit and couple it out to the second reflector at the second position, and to convert the initial delayed signal reflected back by the second reflector into the high-order mode signal in the optical delay line and couple it out to the optical delay line at the second position. The apparatus of claim 5 or 6, wherein The mode conversion element further includes a second optical transmission element and a third mode converter. The second optical transmission element is connected between the beam splitter of the second frequency modulation optoelectronic circuit, the mixer in the second frequency modulation optoelectronic circuit, and the first end of the third mode converter. The second end of the third mode converter is coupled to the second position of the optical delay line. The second position is located between the second mode converter and the second end of the optical delay line. The second optical transmission element is used to transmit the second optical signal from the beam splitter in the second frequency-modulated optoelectronic circuit to the third mode converter, and to transmit the delayed signal from the third mode converter to the mixer in the second frequency-modulated optoelectronic circuit. The third mode converter is used to convert the second optical signal from the second optical transmission element into a higher-order mode signal in the optical delay line and couple it into the optical delay line at the second position; and to convert the higher-order mode signal after two delay processing by the optical delay line into a delayed signal in the second frequency-modulated optoelectronic circuit and couple it out to the second optical transmission element at the second position. The reflective element is also used to reflect the higher-order mode signal after the initial delay of the optical delay line back to the optical delay line. The apparatus of claim 9, wherein The reflective element includes a fourth mode converter and a second reflector. One end of the fourth mode converter is connected to the second reflector, and the other end is coupled to a first position of the optical delay line. The first position is located between the first mode converter and the first end of the optical delay line. The fourth mode converter is used to convert the high-order mode signal after the initial delay of the optical delay line into the initial delayed signal in the second frequency-modulated optoelectronic circuit and couple it out to the second reflector at the first position, and to convert the initial delayed signal reflected back by the second reflector into the high-order mode signal in the optical delay line and couple it out to the optical delay line at the first position. The apparatus of any one of claims 3, 4, 7-9, wherein The second frequency-modulated photoelectric circuit has N components: N first positions corresponding to N second frequency-modulated optoelectronic circuits are sequentially arranged between the first mode converter and the first end of the optical delay line, wherein the cross-sectional dimensions of the optical delay line are different at the N first positions; and / or, The N second positions corresponding to the N second frequency modulation optoelectronic circuits are arranged sequentially between the second mode converter and the second end of the optical delay line, and the cross-sectional dimensions of the optical delay line are different at the N second positions. The apparatus as claimed in claim 11, characterized in that, The cross-sectional dimensions of the optical delay line at the N first positions show an increasing trend; and / or, The cross-sectional dimensions of the optical delay line at the N second positions show an increasing trend. The apparatus of claim 11 or 12, wherein The optical delay line is provided with an adiabatic mode converter between any two adjacent positions in the N first positions and / or any two adjacent positions in the second positions. The apparatus of any one of claims 2 to 13, wherein The first and second mode converters are adiabatic mode converters, and the third and fourth mode converters are directional couplers. The apparatus of any one of claims 1 to 14, wherein The optical delay line is either an optical fiber delay line or an on-chip integrated waveguide delay line. The apparatus of any one of claims 1 to 15, wherein In each of the frequency-modulated photoelectric circuits: It also includes a target measurement path, wherein the beam splitting element has a first output terminal, a second output terminal and a third output terminal, the first output terminal is connected to the mode conversion element, the second output terminal is connected to the mixer, and the third output terminal is connected to the target measurement path; The beam splitter is used to split the light signal output from the light source into a delay signal, a local oscillator signal, and a detection signal, and outputs the delay signal through a first output terminal, the local oscillator signal through a second output terminal, and the detection signal through a third output terminal. The mixer is used to perform mixing processing on the local oscillator signal and the delayed signal; The target measurement path is used to perform target measurement using the detection signal. The apparatus of claim 15, wherein The beam splitting element includes a first beam splitter and a second beam splitter. The first output terminal of the first beam splitter is connected to the input terminal of the second beam splitter, the second output terminal of the first beam splitter is connected to the target measurement path, the first output terminal of the second beam splitter is connected to the mode conversion element, and the second output terminal of the second beam splitter is connected to the mixer. The first beam splitter is used to split the detection signal and the intermediate light signal from the light signal output by the light source, output the intermediate light signal through its first output terminal, and output the detection signal through its second output terminal; The second beam splitter is used to split the local oscillator signal and the signal to be delayed from the intermediate optical signal, output the signal to be delayed through its first output terminal, and output the local oscillator signal through its second output terminal. The apparatus of any one of claims 1 to 17, wherein In each of the frequency-modulated photoelectric circuits: It also includes an amplifier and an analog-to-digital converter, the amplifier and the analog-to-digital converter being connected between the mixer and the light source; The amplifier is used to amplify the intermediate frequency signal obtained by the mixer. The analog-to-digital converter is used to perform analog-to-digital conversion on the amplified intermediate frequency signal to obtain a digital signal. A detection device, characterized in that Includes the signal processing apparatus as described in any one of claims 1 to 18. A terminal device, characterized by comprising: Includes the detection device as described in claim 19.

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