A signal processing device, a detection device and a terminal device

Abstract

A signal processing device, a detection device, and a terminal device are disclosed, relating to the field of detection technology, to reduce the cost and space occupied by optical delay lines. The signal processing device includes a frequency-modulated optoelectronic circuit, which comprises a light source, a first beam splitter, a polarization processing element, an optical delay line, a first reflector, a second reflector, a mixer, a photodetector, a processing element, and a driving circuit. The first end of the polarization processing element is connected to the first beam splitter, the second end is connected to the first end of the optical delay line, the third end is connected to the second reflector, and the fourth end is connected to the mixer. The second end of the optical delay line is connected to the first reflector. By setting the polarization processing element and two or more reflectors in a connected relationship, the optical signal can pass through the same optical delay line four times, thereby multiplexing the same optical delay line to achieve four delays for the optical signal, effectively shortening the length of the optical delay line in the signal processing device and reducing its cost and space occupation.

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.

[0005] Summary of the Invention

[0006] 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.

[0007] In a first aspect, this application provides a signal processing device, including a frequency modulation optoelectronic circuit. The frequency modulation optoelectronic circuit includes a light source, a first beam splitter, a polarization processing element, an optical delay line, a first reflector, a second reflector, a mixer, a photodetector, a processing element, and a driving circuit. The polarization processing element has a first end, a second end, a third end, and a fourth end. The first end is connected to the first beam splitter, the second end is connected to the first end of the optical delay line, the third end is connected to the second reflector, the fourth end is connected to the mixer, and the second end of the optical delay line is connected to the first reflector.

[0008] Based on the above structure, by setting a polarization processing element and two reflective elements in the frequency-modulated optoelectronic circuit, the signal to be delayed in the frequency-modulated optoelectronic circuit can pass through the same optical delay line four times, thus multiplexing the same optical delay line to achieve four delays of the signal to be delayed. In this way, compared with existing technologies, the physical length of the optical delay line in a frequency-modulated optoelectronic circuit can be reduced by 3 / 4 without reducing the delay time of the signal to be delayed. Thus, the original delay effect can be maintained while effectively reducing the size and cost of the optical delay line. It is understandable that when the above signal processing device is applied to detection devices, such as FMCW LiDAR, the length of the optical delay line that needs to be set in the FMCW LiDAR can be reduced, simplifying the FMCW LiDAR system architecture and reducing the system cost.

[0009] In one possible design, within the polarization processing element, there is unidirectional transmission between the first and second ends, bidirectional transmission between the second and third ends, and unidirectional transmission between the second and fourth ends. Based on this connection, the polarization processing element receives the optical signal split by the first beam splitter from the first end and outputs the optical signal from the second end of the polarization processing element, causing the optical signal to enter the optical delay line for the first delay processing. The delayed optical signal is output from the second end of the optical delay line and reflected back to the optical delay line by the first reflector for the second delay processing. The optical signal after the second delay returns to the second end of the polarization processing element, is then output from the third end of the polarization processing element, reflected back to the third end of the polarization processing element by the second reflector, and then output from the second end of the polarization processing element again to re-enter the optical delay line for the third delay processing. It is then output from the second end of the optical delay line and reflected back to the optical delay line by the first reflector for the fourth delay processing. The optical signal after the fourth delay returns to the second end of the polarization processing element and is output from the fourth end of the polarization processing element, entering the mixer.

[0010] Based on the above design, by configuring the internal connection relationship and control logic of each port of the polarization processing element, the optical signal can pass through the same optical delay line four times, thus shortening the length of the optical delay line.

[0011] In one possible design, the optical signal after being split by the first beam splitter is first linearly polarized light. This first linearly polarized light is converted into first circularly polarized light by a polarization processing element and output to an optical delay line. After passing through the optical delay line, it enters the first reflector and is reflected by the first reflector to become second circularly polarized light. The second circularly polarized light passes through the optical delay line and enters the polarization processing element, where it is converted into second linearly polarized light and output to the second reflector. The second linearly polarized light is reflected back to the polarization processing element by the second reflector, where it is converted into third circularly polarized light and output to the optical delay line. The third circularly polarized light passes through the optical delay line and enters the first reflector, where it is reflected to become fourth circularly polarized light and enters the optical delay line. The fourth circularly polarized light passes through the optical delay line and enters the polarization processing element, where it is converted into third linearly polarized light and output to the mixer.

[0012] Based on the above design, the polarization processing element can be used to convert the linear polarization state and circular polarization state of the optical signal. The same optical delay line can be multiplexed four times through one polarization processing element and two reflection elements on the optical path. This makes the length of the optical delay line in the signal processing device only 1 / 4 of the length in the prior art for the same delay time, resulting in a very simple signal processing device architecture.

[0013] In a further possible design, the first linearly polarized light has the same linear polarization state as the third linearly polarized light, and the first linearly polarized light has the same or orthogonal linear polarization state as the second linearly polarized light.

[0014] Based on the above design, the third linearly polarized light has the same polarization state as the first linearly polarized light, ensuring that the optical signal output from the polarization processing element to the mixer has the same polarization state as the optical signal input to the polarization processing element, thus ensuring the accuracy of subsequent mixing operations. Furthermore, the second linearly polarized light has the same or orthogonal polarization state as the first linearly polarized light, enabling the signal processing device to support more frequency modulation scenarios and improving its versatility.

[0015] In a further possible design, the first circularly polarized light has the same circular polarization state as the fourth circularly polarized light, and the second circularly polarized light has the same circular polarization state as the third circularly polarized light.

[0016] Based on the above design, the correlation between the circular polarization states of four circularly polarized lights can be used to realize the correlation between the three linearly polarized lights obtained by converting or converting the four circularly polarized lights. For example, if the second and third circularly polarized lights have the same circular polarization state, it can be ensured that the linear polarization state of the optical signal after the second delay of the optical delay line is the same as that of the optical signal after the third delay of the optical delay line. This, in turn, ensures that the first and fourth circularly polarized lights have the same circular polarization state. In this way, the third linearly polarized light obtained by converting the fourth circularly polarized light will have the same linear polarization state as the first linearly polarized light, which can improve the subsequent mixing effect.

[0017] In one possible design, the polarization processing element includes a polarization light transmission element and a polarization light adjustment element. Both the polarization light transmission element and the polarization light adjustment element have 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 of the polarization light transmission element is unidirectional. The first end of the polarization light transmission element is connected to a first beam splitter, the second end of the polarization light transmission element is connected to the first end of the polarization light adjustment element, and the third end of the polarization light transmission element is connected to a mixer. The second end of the polarization light adjustment element is connected to the first end of an optical delay line, and the third end of the polarization light adjustment element is connected to a second reflection element.

[0018] Based on the above design, the polarization transmission element can be used to transmit polarized light, and the polarization adjustment element can be used to convert the polarization of light. Combined with the reflection of polarized light by two reflecting elements, the effect of polarized light passing through the optical delay line four times can be achieved. Furthermore, based on the unidirectional transmission characteristic of the three ports of the optical transmission element, as much of the optical signal as possible can enter the optical delay line for delay processing, and as much of the delayed optical signal as possible can enter the mixer, thereby improving the signal delay effect and mixing effect.

[0019] In one example of the design above, the polarization transmission element is a circulator. Circulators have low cost and small size, and are easy to implement.

[0020] In one example of the above design, the polarization adjustment element can be any of the following structures one through four:

[0021] Structure 1: The polarization adjustment element includes a polarization beam splitter (PBS) and a quarter-wave plate. The PBS has a first end, a second end, and a third end. P-light or TE-light is transmitted between the first end and the second end of the PBS, and S-light or TM-light is reflected between the second end and the third end of the PBS. The first end of the PBS is connected to the polarization transmission element, the second end of the PBS is connected to the first end of the quarter-wave plate, the second end of the quarter-wave plate is connected to the first end of the optical delay line, and the third end of the PBS is connected to the second reflection element.

[0022] Structure 2: The polarization adjustment element includes a PBS and a quarter-wave plate. The PBS has a first end, a second end, and a third end. P-light or TE-light is transmitted between the first end and the second end of the PBS, and S-light or TM-light is reflected between the second end and the third end of the PBS. The first end of the PBS is connected to a second reflective element, the second end of the PBS is connected to the first end of the quarter-wave plate, the second end of the quarter-wave plate is connected to the first end of the optical delay line, and the third end of the PBS is connected to a polarization transmission element.

[0023] Based on the above structures one and two, the transmission of P-light or TE-light in the PBS, the reflection of S-light or TM-light in the PBS, and the conversion of light polarization by the quarter-wave plate can be used to achieve four-fold multiplexing of the same optical delay line through a PBS, a quarter-wave plate, and two reflective elements on the optical path. Among them, the PBS and the quarter-wave plate are relatively common devices with low cost and simple structure.

[0024] In one example of Structure 1 above, the first linearly polarized light is either P-polarized or TE-polarized. Therefore, Structure 1 is suitable for scenarios where the light source outputs a P-polarized or TE-polarized light signal. Furthermore, Structure 1 can ensure that both the light signal output to the mixer and the light signal input to the polarization processing element remain P-polarized or TE-polarized, significantly reducing the length of the optical delay line in the signal processing device while maintaining good mixing performance.

[0025] In one example of Structure 2 above, the first linearly polarized light is either S-polarized or TM-polarized. Therefore, Structure 2 is suitable for scenarios where the light source outputs an S-polarized or TM-polarized light signal. Furthermore, Structure 2 can ensure that both the light signal output to the mixer and the light signal input to the polarization processing element remain S-polarized or TM-polarized, significantly reducing the length of the optical delay line in the signal processing device while maintaining good mixing performance.

[0026] Understandably, the connection relationships between the three ports of the PBS and other components in Structure 1 and Structure 2 are different. Therefore, by designing the connection relationships between the three ports of the PBS and the quarter-wave plate and the two reflecting elements, the signal processing device can be adapted to input signals with different linear polarization states, thereby improving the versatility of the signal processing device.

[0027] Structure 3 includes a polarization processing element comprising a polarization splitter rotator (PSR) and a quarter-wave plate. The PSR has a first end, a second end, and a third end. The first and second ends of the PSR transmit optical signals in the original polarization direction, while the second and third ends transmit optical signals in the polarization direction after a 90° rotation. The first end of the PSR is connected to a polarization transmission element, the second end of the PSR is connected to the first end of the quarter-wave plate, the second end of the quarter-wave plate is connected to the first end of an optical delay line, and the third end of the PSR is connected to a second reflection element.

[0028] Structure four includes a polarization processing element comprising a polarization splitter rotator (PSR) and a quarter-wave plate. The PSR has a first end, a second end, and a third end. The first and second ends of the PSR transmit optical signals in the original polarization direction, while the second and third ends of the PSR transmit optical signals in the polarization direction after a 90° rotation. The first end of the PSR is connected to a second reflecting element, the second end of the PSR is connected to the first end of the quarter-wave plate, the second end of the quarter-wave plate is connected to the first end of the optical delay line, and the third end of the PSR is connected to a polarization light transmission element.

[0029] Based on the above structures three and four, the characteristics of PSR in transmitting P-light and S-light separately and converting P-light to S-light, or in transmitting TM-light and TE-light separately and converting TE-light to TM-light, as well as the polarization conversion of light by the quarter-wave plate, can be used to achieve four-fold multiplexing of the same optical delay line through a PSR, a quarter-wave plate, and two reflective elements on the optical path. PSR and quarter-wave plate are relatively common devices with low cost and simple structure.

[0030] In one example of structure three or four above, the first linearly polarized light is P-light or TE-light. Therefore, structure three or four above is suitable for scenarios where the light source outputs a P-light or TE-light signal. Simultaneously, structure three or four above can also ensure that both the light signal output to the mixer and the light signal input to the polarization processing element remain P-light or TE-light, significantly shortening the length of the optical delay line in the signal processing device while maintaining good mixing performance.

[0031] In one example of the above design, there are N frequency-modulated optoelectronic circuits, where N is an integer greater than or equal to 2. In this case, the signal processing device may also include a beam combining element and a second beam splitting element. The N input terminals of the beam combining element are connected one-to-one to the N first beam splitting elements in the N frequency-modulated optoelectronic circuits. The output terminal of the beam combining element is connected to the first terminal of the polarization light transmission element. The input terminal of the second beam splitting element is connected to the third terminal of the polarization light transmission element. The N output terminals of the second beam splitting element are connected one-to-one to the N mixers in the N frequency-modulated optoelectronic circuits.

[0032] Based on the above design, the beam combiner can combine optical signals from N first beam splitters in N frequency-modulated optoelectronic circuits into a single optical signal and send it to the polarization transmission element. The second beam splitter can divide the optical signal from the polarization transmission element (after four delays) into four delayed optical signals for each of the N frequency-modulated optoelectronic circuits and send them to the N mixers in the N frequency-modulated optoelectronic circuits. This allows N frequency-modulated optoelectronic circuits to share the same optical delay line, significantly reducing the number of optical delay lines required in the signal processing device, achieving a minimalist architecture and extremely low cost for the signal processing device.

[0033] In one possible design, the optical delay line can be a fiber optic delay line or a waveguide delay line integrated on a chip. This allows the signal processing device to be adapted to a variety of optical delay lines, thus providing versatility.

[0034] In one possible design, the reflective element can be a fiber optic ring mirror, a Bragg grating, or a Sagnac ring. This allows for beam reflection at a relatively low cost.

[0035] In one possible design, the frequency-modulated optoelectronic circuit may further include a target measurement path. A first beam splitter has an input terminal, a first output terminal, a second output terminal, and a third output terminal. A mixer has a first input terminal, a second input terminal, and an output terminal. The input terminal of the first beam splitter is connected to a light source. The first output terminal of the first beam splitter is connected to the first terminal of a polarization processing element. The second output terminal of the first beam splitter is connected to the second input terminal of the mixer. The third output terminal of the first beam splitter is connected to the target measurement path. The first input terminal of the mixer is connected to the fourth terminal of the polarization processing element. Based on this structure and connection relationship, the first beam splitter is used to split the light beam generated by the light source to obtain a local oscillator signal, a signal to be delayed, and a detection signal. It outputs the signal to be delayed through its first output terminal, the local oscillator signal through its second output terminal, and the detection signal through its third output terminal. The mixer is used to mix the local oscillator signal and the delayed signal. The target measurement path is used to perform target measurement using the detection signal.

[0036] Based on the above design, 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.

[0037] In one example of the above design, the first 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, and 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 first terminal of the polarization processing element, and the second output terminal of the second beam splitter is connected to the mixer. Based on this structure and connection relationship, the first beam splitter is used to split the light beam generated by the light source to obtain a probe signal and an intermediate light signal, outputting the intermediate light 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 light signal to obtain 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.

[0038] Based on the above example, the function of the first beam splitting element can be achieved by two beam splitters. The beam splitters are low in cost and small in size, which helps to achieve small size and low cost of signal processing device.

[0039] In one example of the above design, the signal processing device includes N frequency-modulated photoelectric circuits. The N frequency-modulated photoelectric circuits share the same target measurement path, or have their own target measurement paths, or partially share the same target measurement path and partially have their own target measurement paths, where N is an integer greater than or equal to 2.

[0040] Based on the above examples, the signal processing device can be applied to various occasions with or without shared target measurement paths. By sharing the target measurement path, the detection signals after multiple frequency-modulated photoelectric circuits are split can be combined into one signal and then 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 of the measured target.

[0041] In one possible design, the frequency modulation optoelectronic circuit may also include an amplifier and an analog-to-digital converter (ADC). The amplifier and ADC are connected between the photodetector and the processing element. The amplifier is used to amplify the intermediate frequency (IF) signal from the photodetector, and the ADC is used to convert the amplified IF signal to a digital signal.

[0042] Based on the above design, the power of the intermediate frequency signal is amplified by the 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 the software analysis of the subsequent processing components.

[0043] 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.

[0044] 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.

[0045] 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

[0046] Figure 1a illustrates an exemplary schematic diagram of the linear relationship between the emitted beam and the modulated signal;

[0047] Figure 1b illustrates an exemplary schematic diagram of the nonlinear relationship between the emitted beam and the modulated signal;

[0048] Figure 2 illustrates a possible application scenario to which this application applies;

[0049] Figure 3a illustrates an exemplary architecture diagram of a mainstream direct-modulation FMCW LiDAR;

[0050] Figure 3b illustrates, exemplarily, a schematic diagram of the structure of a single-laser direct-modulated FMCW LiDAR provided in the industry;

[0051] Figure 3c illustrates a schematic diagram of a direct-modulated FMCW LiDAR with multiple lasers provided in the industry.

[0052] Figure 4 illustrates a schematic diagram of the structure of a signal processing device provided in this application;

[0053] Figure 5 illustrates a schematic diagram of another signal processing device provided in this application;

[0054] Figure 6 illustrates a schematic diagram of another signal processing device provided in this application;

[0055] Figure 7 illustrates a schematic diagram of the structure of a polarization processing element provided in this application;

[0056] Figure 8 illustrates a schematic diagram of the structure of a signal processing apparatus provided in Embodiment 1;

[0057] Figure 9a illustrates, by way of example, a schematic diagram of the flow of a signal polarization state provided in Implementation Scheme 1;

[0058] Figure 9b illustrates an exemplary schematic diagram of another signal polarization state transition form provided in Implementation Scheme 1;

[0059] Figure 10a illustrates a possible structural diagram of a PBS provided in Implementation Scheme 1;

[0060] Figure 10b illustrates an exemplary schematic diagram of another possible structure of the PBS provided in Implementation Scheme 1;

[0061] Figure 10c illustrates an exemplary schematic diagram of another possible structure of a PBS provided in Implementation Scheme 1;

[0062] Figure 11 illustrates a schematic diagram of a signal processing device provided in Embodiment 2;

[0063] Figure 12 illustrates an exemplary schematic diagram of the flow form of a signal polarization state provided in Implementation Scheme 2;

[0064] Figure 13 illustrates a possible structural diagram of a PSR provided in Embodiment 2;

[0065] Figure 14 illustrates a schematic diagram of the structure of a signal processing apparatus provided in Embodiment 3;

[0066] Figure 15 illustrates, by way of example, a schematic diagram of the flow of a signal polarization state provided in Implementation Scheme 3;

[0067] Figure 16 illustrates a schematic diagram of a signal processing apparatus provided in Embodiment 4;

[0068] Figure 17 illustrates a schematic diagram of a signal processing apparatus provided in Embodiment 5;

[0069] Figure 18a illustrates a schematic diagram of a signal processing apparatus provided in Embodiment Six;

[0070] Figure 18b illustrates a schematic diagram of the structure of a signal processing apparatus provided in Embodiment Seven;

[0071] Figure 18c exemplarily illustrates a structural schematic diagram of another signal processing apparatus provided in Embodiment Seven;

[0072] Figure 19 illustrates a schematic diagram of another signal processing apparatus provided in this application;

[0073] Figure 20a illustrates a schematic diagram of another signal processing apparatus provided in this application;

[0074] Figure 20b illustrates a schematic diagram of another signal processing device provided in this application;

[0075] Figure 20c exemplarily illustrates a structural schematic diagram of another signal processing apparatus provided in this application;

[0076] Figure 20d illustrates a schematic diagram of another signal processing apparatus provided in this application;

[0077] Figure 20e illustrates a schematic diagram of another signal processing apparatus provided in this application;

[0078] Figure 21 illustrates a schematic diagram of the structure of a detection device provided in this application;

[0079] Figure 22 illustrates a schematic diagram of the structure of a terminal device provided in this application. Detailed Implementation

[0080] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0081] 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.

[0082] I. Linear polarized light

[0083] Linearly polarized light, also known as linearly polarized light, linearly polarized state light, or plane-polarized light, refers to light in which the electric vector at each point along the direction of propagation lies within a defined plane. Since the trajectory of the electric vector endpoints is a straight line, it is called linearly polarized light. The plane formed by the direction of the light vector and the direction of light propagation is called the plane of vibration. The plane of vibration of linearly polarized light is fixed and does not undergo deflection.

[0084] II. Circular Polarizing Light

[0085] Circularly polarized light, also known as circularly polarized light or light in a circularly polarized state, refers to light whose rotating electric vector endpoint traces a circular trajectory. It is a special case of elliptically polarized light. When the propagation directions are the same, the vibration directions are perpendicular, and the phase difference is constant, circular polarization occurs. Two plane-polarized lights, when superimposed, can synthesize circularly polarized light with a regularly changing electric vector. The magnitude of the electric vector of the circularly polarized light remains constant, while its direction changes uniformly with time. The phase difference is... The light is left-handed circularly polarized, with a phase difference of . It is right-handed circularly polarized light.

[0086] III. Polarization Direction

[0087] The polarization direction is also called the polarization direction or polarization state. This is because there is a certain characteristic direction in the polarization element, called the polarization direction. The polarization element only allows vibrations parallel to the polarization direction to pass through, while absorbing or reflecting light that vibrates perpendicular to that direction.

[0088] IV. P-light, S-light, TE-light, TM-light

[0089] P-rays, S-rays, TE-rays, and TM-rays are all linearly polarized light, also known as P-polarized light, S-polarized light, TE-polarized light, and TM-polarized light. P-rays and S-rays represent light with different polarization directions in space. Simply put, in space, the light vector is decomposed into two mutually perpendicular vibration directions. The light with the vibration direction within the plane of incidence is called the parallel component of the light vector, or simply P-ray, and the light with the vibration direction perpendicular to the plane of incidence is called the perpendicular component of the light vector, or simply S-ray. TE-rays and TM-rays represent light with different polarization directions from a chip integration perspective, and are often used to describe the propagation characteristics of electromagnetic waves. TE-rays are also called transverse electric waves, where the electric field component is perpendicular to the propagation direction of the electromagnetic wave; that is, the electric field component is parallel to the plane of incidence. TM-rays are also called transverse magnetic waves, where the magnetic field component is perpendicular to the propagation direction of the electromagnetic wave; that is, the electric field direction is perpendicular to the plane of incidence.

[0090] V. Quarter wave plate

[0091] A quarter-wave plate, also known as a quarter-retarder plate or λ / 4 waveplate, is used to transmit light normally incident through a waveplate. The phase difference between the outgoing ordinary (o) and extraordinary (e) rays is equal to one-quarter of the wavelength. In an optical path, a quarter-wave plate is commonly used to convert linearly polarized light into circularly polarized or elliptically polarized light; or, to convert circularly polarized or elliptically polarized light into linearly polarized light. For example, when linearly polarized light is incident perpendicularly to a quarter-wave plate, and the polarization of the light forms an angle θ with the optical axis of the quarter-wave plate (perpendicular to the natural split plane), the emitted light is elliptically polarized. When θ = 45°, the emitted light is circularly polarized. For instance, when P-polarized light is incident on a quarter-wave plate at a 45° angle, it emerges as circularly polarized light; when it is incident on the quarter-wave plate again, it emerges as S-polarized light. When S-polarized light is incident on a quarter-wave plate at a 45° angle, it emerges as circularly polarized light. When it is incident on the quarter-wave plate again, it emerges as P-polarized light.

[0092] When light propagates in a uniaxial crystal and undergoes birefringence, one of the two refracted beams always obeys the ordinary law of refraction. This beam is called the ordinary light (o-ray) or simply the o-ray. The polarized light that is perpendicular to the vibration direction of the o-ray is called the extraordinary light (e-ray).

[0093] VI. Frequency mixing.

[0094] 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 proportional to the target distance. It also contains information about the Doppler effect caused by the target's movement, based on which the target's velocity can be calculated.

[0095] VII. Polarizing Beam Splitter (PBS)

[0096] A polarization beam splitter (PBS) is an optical device used to couple orthogonally linearly polarized light from a single-mode fiber or polarization-maintaining fiber into two separate polarization-maintaining fibers for output. For example, it can split a beam of light synthesized from TE and TM light into TE and TM light for separate output, or split a beam of light synthesized from P and S light into P and S light for separate output. PBS implementations include, but are not limited to, polarization beam splitters.

[0097] PBS can also be used in reverse, that is, to couple two orthogonally linearly polarized beams input from a polarization-maintaining fiber into a single-mode fiber or a polarization-maintaining fiber for output. For example, TE and TM beams can be combined into one beam for output, or P and S beams can be combined into one beam for output. In this case, PBS becomes a polarizing beam combiner (PBC).

[0098] 8. Polarization Rotation Beam Splitter (PSR)

[0099] A PSR is an optical device that integrates the functions of a PBS (polarization rotator) and a polarization rotator (PR). It can separate two linearly polarized lights and convert the polarization direction of one of the linearly polarized lights to the other polarization direction. For example, it can separate TM (transient beam) and TE (transient beam) light and convert the TM light into TE light, or separate S (transient beam) and P (transient beam) light and convert the S light into P light.

[0100] PSR can also be used in reverse, that is, the polarization direction of one linearly polarized light is converted to another polarization direction and then combined with another linearly polarized light to output a beam. For example, one of two TE beams is converted into a TM beam and then combined with the other TE beam to output a beam, or one of two P beams is converted into an S beam and then combined with the other P beam to output a beam.

[0101] The preceding text introduced some of the terms used in this application. The following text introduces the possible application scenarios of this application.

[0102] 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.

[0103] 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…

[0104] 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.

[0105] 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.

[0106] 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.

[0107] Figure 3a shows a schematic diagram of a mainstream direct-modulation FMCW LiDAR architecture. This direct-modulation FMCW LiDAR 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. When the direct-modulation FMCW LiDAR is working, 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 splits 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 modulation signal L1 input to the light source.

[0108] 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 FMCW LiDAR 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.

[0109] Based on the single-laser direct-modulation FMCW LiDAR 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 FMCW LiDAR, 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 FMCW LiDAR 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 FMCW LiDAR. In a single-laser direct-modulation FMCW LiDAR, 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-scale delay lines by N results in a very large size and high hardware cost, occupying a significant amount of space within the FMCW LiDAR.

[0110] In view of this, this application provides a signal processing apparatus that utilizes a polarization processing element and two reflecting elements to ensure that the signal light to be delayed passes through the same optical delay line four times, thereby multiplexing the same optical delay line to achieve four delays of the signal light to be delayed, greatly reducing the length of the optical delay line required in the signal processing apparatus. Furthermore, when applied to a multi-laser direct-modulated FMCW LiDAR, the multiple reference calibration paths corresponding to the multiple lasers can also share the same optical delay line, thereby reducing the number of optical delay lines, further reducing the size and hardware cost of the optical delay lines, and reducing the space occupied by the optical delay lines in the direct-modulated FMCW LiDAR.

[0111] The signal processing apparatus proposed in this application will now be described in detail with reference to Figures 4 to 20e.

[0112] 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.

[0113] 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 frequency-modulated photoelectric circuit 110, which includes a light source 111, a first beam splitter 112, a polarization processing element 210, an optical delay line 310, a first reflective element 411, a second reflective element 412, a mixer 114, a photodetector 115, a processing element 116, and a driving circuit 117. The optical delay line 310 has a first end (a1) and a second end (a2). The polarization processing element 210 is connected between the first beam splitter 112, the mixer 114, the second reflective element 412, and the first end (a1) of the optical delay line 310. The second end (a2) of the optical delay line 310 is connected to the first reflective element 411. For example, the polarization processing element 210 has a first end (b1), a second end (b2), a third end (b3) and a fourth end (b4). The first end b1 is connected to the first beam splitter 112, the second end b2 is connected to the first end a1 of the optical delay line 310, the third end b3 is connected to the second reflector 412, and the fourth end b4 is connected to the mixer 114.

[0114] Optionally, as shown in Figure 4, within the polarization processing element 210, there is unidirectional transmission between the first end b1 and the second end b2, bidirectional transmission between the second end b2 and the third end b3, and unidirectional transmission between the second end b2 and the fourth end b4. Based on this structure and connection, the optical signal split by the first beam splitter 112 enters the first end b1 of the polarization processing element 210, and is output from the second end b1 of the polarization processing element 210 into the optical delay line 310. After the first delay processing by the optical delay line 310, it is output from the second end a2 of the optical delay line 310 into the first reflecting element 411, and then reflected back to the second end a2 of the optical delay line 310. After the second delay processing by the optical delay line 310, it is output from the first end a1 of the optical delay line 310 into the second end b2 of the polarization processing element 210, and then output from the third end b3 of the polarization processing element 210 into the second end b4. The reflective element 412 is reflected back to the third end b3 of the polarization processing element 210 by the second reflective element 412, and outputs from the second end b2 of the polarization processing element 210, re-enters the optical delay line 310, and after the third delay processing of the optical delay line 310, it is output from the second end a2 of the optical delay line 310 and enters the first reflective element 411. Then it is reflected back to the second end a2 of the optical delay line 310 by the first reflective element 411, and after the fourth delay processing of the optical delay line 310, it is output from the first end a1 of the optical delay line 310 and enters the second end b2 of the polarization processing element 210. Then it is output from the fourth end b4 of the polarization processing element 210 and enters the mixer 114.

[0115] From the perspective of polarization state, if the optical signal after being split by the first beam splitter 112 is a linearly polarized light R1, then: the polarization processing element 210 receives the linearly polarized light R1 after being split by the first beam splitter 112 from its first end b1, converts it into circularly polarized light, and outputs it from its second end b2; the circularly polarized light enters the optical delay line 310 from its first end a1, undergoes delay processing by the optical delay line 310, and is output from its second end a2, entering the first... The first reflector 411 reflects the second circularly polarized light, which then becomes the second circularly polarized light. The second circularly polarized light enters the optical delay line 310 from its second end a2, undergoes delay processing, and then exits from its first end a1, returning to the second end b2 of the polarization processing element 210. The polarization processing element 210 converts the second circularly polarized light input from its second end b2 into a second linearly polarized light R1”, which is then output from its third end b3, making the second linearly polarized light R1”... "Enters the second reflecting element 412 and is reflected back to the third end b3 of the polarization processing element 210; the polarization processing element 210 converts the second linearly polarized light R1 input at the third end b3 into third circularly polarized light and outputs it from its second end b2; the third circularly polarized light enters the optical delay line 310 from the first end a1, undergoes delay processing by the optical delay line 310, and is output from the second end a2 of the optical delay line 310, enters the first reflecting element 411, and is then reflected back to the third end b3 of the polarization processing element 210. After reflection by a reflective element 411, the light becomes the fourth circularly polarized light. The fourth circularly polarized light enters the optical delay line 310 from the second end a2. After being delayed by the optical delay line 310, it is output from the first end a1 of the optical delay line 310 and returns to the second end b2 of the polarization processing element 210. The polarization processing element 210 converts the fourth circularly polarized light input from the second end b2 into the third linearly polarized light R1”” and outputs it from its fourth end b4, so that the third linearly polarized light R1”” enters the mixer 114.

[0116] Based on the above, by setting a polarization processing element 210 and two reflective elements 411 and 412 in the frequency modulation optoelectronic circuit, the optical signal to be delayed in the frequency modulation optoelectronic circuit can pass through the same optical delay line 310 four times, thus multiplexing the same optical delay line 310 to achieve four delays for the optical signal to be delayed. Compared with the prior art, the physical length of the optical delay line in a frequency modulation optoelectronic circuit can be reduced by 3 / 4 without reducing the delay time of the optical signal to be delayed. In this way, the original delay effect can be maintained while reducing the size and cost of the optical delay line.

[0117] The above signal processing devices can be applied to the field of nonlinear frequency modulation (FFM) to achieve functions such as frequency sweep monitoring, nonlinear calibration (also known as FFM signal predistortion), or real-time feedback control loops for electro-optical phase-locked loops (EOPLL). The nonlinear frequency modulation field can include, but is not limited to, FMCW, optical frequency domain reflectometry (OFDR) systems, or other nonlinear frequency modulation systems. When applied to FMCW LiDBRs, they can significantly reduce the space occupied by optical delay lines in the FMCW LiDBR, simplify the FMCW LiDBR architecture design, and reduce the cost of the FMCW LiDBR.

[0118] In a signal processing device, the frequency-modulated photoelectric circuit 110 can be understood as a loop formed by the signal transmission between its various internal components. For example, as shown in Figure 4, the light source 111, the first beam splitter 112, the polarization processing element 210, the mixer 114, the photodetector 115, the processing element 116, and the driving circuit 117 in the frequency-modulated photoelectric circuit 110 are connected end to end to form a loop. The signal flow of this loop is as follows: the light source 111 outputs linearly polarized light R; the first beam splitter 112 splits the linearly polarized light R into a delayed optical signal R1 and other optical signals (not shown in the figure, see Figure 5 below for details); the delayed optical signal R1 passes through the polarization processing element 210, the optical delay line 310, and the first reflector... The reflective element 411 and the second reflective element 412 undergo four delay processes before being transmitted to the mixer 114 for mixing with other signals (not shown in the figure, but can be seen in Figure 5 below) to obtain the intermediate frequency signal Z. The intermediate frequency signal Z is detected by the photodetector element 115 and output to the processing element 116. The processing element 116 sends a feedback signal P to the drive circuit 117 based on the detected intermediate frequency signal Z. The drive circuit 117 adjusts the modulation signal L output to the light source 111 based on the feedback signal P to calibrate the linearity between the modulation signal L and the light signal R output by the light source 111.

[0119] To further illustrate the signal flow in the circuit, please refer to Figure 5, which shows a schematic diagram of another signal processing device provided in this application. Optionally, as shown in Figure 5, in the frequency modulation photoelectric circuit 110, the first beam splitter 112 may have an input terminal and a first output terminal (c 11 ) and second output terminal (c 12 The mixer 114 may have an output terminal and a first input terminal (d). 11 ) and second input terminal (d 12 The input terminal of the first beam splitter 112 is connected to the output terminal of the light source 111, and the first output terminal c of the first beam splitter 112 is connected to the output terminal of the light source 111. 11The first terminal b1 of the polarization processing element 210 and the second output terminal c of the first beam splitting element 112 are connected. 12 Connect to the second input terminal d of mixer 114 12 The first input terminal d of mixer 114 11 The fourth terminal b4 of the polarization processing element 300 is connected. Based on this connection, the first beam splitter 112 can perform beam splitting processing on the optical signal R output from the light source 111 to obtain the optical signal R1 to be delayed and the local oscillator signal of the calibration path, which are then transmitted through its first output terminal c. 11 Output the optical signal R1 to be delayed, and output it through its second output terminal c. 12 The local oscillator signal of the calibration path is output. This calibration path local oscillator signal is directly input to the second input terminal d of mixer 114. 12 The optical signal R1 to be delayed undergoes four delay processes—polarization processing element 210, optical delay line 310, first reflection element 411, and second reflection element 412—before entering the first input terminal d of mixer 114. 11 Mixer 114 is aligned with its first input terminal d. 11 The received optical signal R1”” after four delays and its second input terminal d 12 The received calibration path local oscillator signal is mixed to obtain the intermediate frequency signal Z.

[0120] Further, optionally, as shown in Figure 5, the frequency modulation optoelectronic circuit 110 may also include an amplifier 118 and / or an analog-to-digital converter (ADC) 119. When the amplifier 118 is included, it can be connected between the photodetector 115 and the processing element 116 to amplify the intermediate frequency (IF) signal Z detected by the photodetector 115. When the ADC 119 is included, it can be connected between the photodetector 115 and the processing element 116 to perform analog-to-digital conversion on the IF signal Z detected by the photodetector 115 to obtain a digital signal. When both the amplifier 118 and the ADC 119 are included, they can be connected in series between the photodetector 115 and the processing element 116. Amplifier 118 can amplify the intermediate frequency signal Z detected by photodetector 115, and then input the amplified intermediate frequency signal Z to analog-to-digital converter 119. Analog-to-digital converter 119 performs analog-to-digital conversion on the amplified intermediate frequency signal Z to obtain a digital signal, and inputs the digital signal to processing element 116.

[0121] Furthermore, optionally, as shown in Figure 5, the frequency-modulated photoelectric circuit 110 may further include a target measurement path 113, and the first beam splitter 112 may further have a third output terminal (c 13 ), third output terminal c 13Connected to the target measurement path 113. The first beam splitter 112 splits the linearly polarized light R output from the light source 111, obtaining not only the optical signal R1 to be delayed and the local oscillator signal of the calibration path, but also a detection signal. The detection signal is output through the third output terminal c. 13 The signal is output to the target measurement channel 113. The target measurement channel 113 receives the detection signal and uses it to perform target measurement.

[0122] As an example, as shown in Figure 6, the target measurement path 113 may include a third beam splitter 1131, a polarization light transmission element 1132, a mixer 1133, a photodetector 1134, an amplifier 1135, an analog-to-digital converter 1136, and a processing element 1137. The polarization light transmission element 1132 has a first end (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 a unidirectional transmission. The input terminal of the third beam splitter 1131 is connected to the third output terminal c of the first beam splitter 112. 13 One output terminal of the third beam splitter 1131 is connected to the first terminal b of the polarization transmission element 1132. 51 The other output is connected to one input of mixer 1133. The second terminal b of polarization transmission element 1132... 52 Oriented toward the probe space, the third end b of the polarization 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.

[0123] Based on the above structure and connection relationship, as shown in Figure 6, in the target measurement path 113, the third beam splitter 1131 can receive the third output terminal c of the first beam splitter 112. 13 The output detection signal is split into a transmitted signal and a target path local oscillator signal. The target path local oscillator signal is directly input to mixer 1133. The transmitted signal originates from the first terminal b of polarization transmission element 1132. 51 Input, from the second end b of the polarization light 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 polarization transmission element 1132 after being reflected by the target. 52 And then from the third end b of the polarization light 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.

[0124] 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.

[0125] It is understandable that the target measurement path 113 may have other structures, and this application does not specifically limit them.

[0126] In a signal processing device, there are many possible structures that can realize the function of polarization processing element 210. For example, it can be a combination of multiple polarization beam splitting elements, or a combination of a multi-port element and one or more polarization beam splitting elements, or a combination of a multi-port element, one or more polarization beam splitting elements and one or more polarization beam combining elements, etc., without limitation.

[0127] As an example, based on the signal processing apparatus shown in FIG5, please refer to FIG7, which shows a possible structural schematic diagram of a polarization processing element 210 provided in this application. In this example, the polarization processing element 210 may include a polarization light transmission element 211 and a polarization light adjustment element 212. The polarization light transmission element 211 is connected between the first beam splitter 112, the polarization light adjustment element 212 and the mixer 114. The polarization light adjustment element 212 is connected between the polarization light transmission element 211, the first end a1 of the optical delay line 310 and the second reflection element 412. For example, the polarization light transmission element 211 has a first end (e1), a second end (e2), and a third end (e3), and the polarization light adjustment element 212 also has a first end (j1), a second end (j2), and a third end (j3). The transmission from the first end e1 to the second end e2 and from the second end e2 to the third end e3 of the polarization light transmission element 211 is unidirectional. The first end e1 of the polarization light transmission element 211 is connected to the first beam splitter 112, the second end e2 of the polarization light transmission element 211 is connected to the first end j1 of the polarization light adjustment element 212, the third end e3 of the polarization light transmission element 211 is connected to the mixer 114, the second end j2 of the polarization light adjustment element 212 is connected to the first end a1 of the optical delay line 310, and the third end j3 of the polarization light adjustment element 212 is connected to the second reflection element 412.

[0128] Based on this structure and connection relationship, as shown in Figure 7, the first beam splitter 112 splits the optical signal R output from the light source into a calibration path local oscillator signal and a first linearly polarized light R1. The calibration path local oscillator signal is emitted from the second output terminal c of the first beam splitter 112. 12 The output is sent to mixer 114, while the first linearly polarized light R1 is output from the first output terminal c of the first beam splitter 112. 11The light is output and enters the first end e1 of the polarization transmission element 211. Since the transmission from the first end e1 to the second end e2 is unidirectional, the first linearly polarized light R1 will be transmitted from the second end e2 of the polarization transmission element 211 to the first end j1 of the polarization adjustment element 212. The polarization adjustment element 212 converts the first linearly polarized light R1 input from the first end j1 into first circularly polarized light and outputs it from the second end j2. This causes the first circularly polarized light to undergo two delay processes, passing through the optical delay line 310, the first reflection element 411, and the optical delay line 310, before becoming second circularly polarized light and returning to the second end j2 of the polarization adjustment element 212. The polarization adjustment element 212 converts the second circularly polarized light input from the second end j2 into second linearly polarized light R1” and outputs it from the third end j3. The second linearly polarized light R1” is reflected back to the third end j3 of the polarization adjustment element 212 by the second reflection element 412. The polarization adjustment element 212 converts the second linearly polarized light R1” input at the third terminal j3 into third circularly polarized light and outputs it from the second terminal j2. This causes the third circularly polarized light to pass sequentially through the optical delay line 310, the first reflective element 411, and the optical delay line 310, undergoing two more delay processes before becoming fourth circularly polarized light and returning to the second terminal j2 of the polarization adjustment element 212. The polarization adjustment element 212 then converts the fourth circularly polarized light input at the second terminal j2 into third linearly polarized light R1”” and outputs it from the first terminal j1. This causes the third linearly polarized light R1”” to enter the second terminal e2 of the polarization transmission element 211. Since the transmission from the second terminal e2 to the third terminal e3 is unidirectional, the third linearly polarized light R1”” will be output from the third terminal e3 of the polarization transmission element 211 and enter the mixer 114, where it will be mixed with the local oscillator signal of the calibration path after being split by the first beam splitter 112.

[0129] Optionally, the polarization state of the first linearly polarized light R1 is the same as the polarization state of the third linearly polarized light R1"" and is the same as or orthogonal to the polarization state of the second linearly polarized light R1"". For example, the first linearly polarized light R1 and the third linearly polarized light R1"" are both P-light or TE-light, and the second linearly polarized light R1"" can be P-light or TE-light, or S-light or TM-light; or, the first linearly polarized light R1 and the third linearly polarized light R1"" are both S-light or TM-light, and the second linearly polarized light R1"" can be P-light or TE-light, or S-light or TM-light, without specific limitations. It can be understood that the third linearly polarized light R1"" has the same polarization state as the first linearly polarized light R1, that is, the optical signal output from the polarization processing element 210 to the mixer 114 has the same polarization state as the optical signal input to the polarization processing element 210, which can ensure the accuracy of subsequent mixing operations. The second linearly polarized light R1"" has the same or orthogonal polarization state as the first linearly polarized light R1, which can support more frequency modulation scenarios and improve the versatility of the signal processing device.

[0130] There are various possibilities for polarization adjustment elements capable of converting linearly polarized light to circularly polarized light. The following describes several possible structures of the polarization adjustment element 212 through different implementation schemes. It should be understood that this application does not limit the polarization adjustment element 212 to only having these structures. Any polarization adjustment element capable of achieving the same polarization state of the output optical signal as the input optical signal, and with the output optical signal delaying the input optical signal four times, is within the scope of protection of this application.

[0131] Implementation Plan 1

[0132] Please refer to Figure 8, which shows a schematic diagram of a signal processing device provided in Embodiment 1. In this example, the polarization adjustment element 212 includes a PBS and a quarter-wave plate. The PBS is connected between the polarization transmission element 211, the quarter-wave plate, and the second reflection element 412. The quarter-wave plate is connected between the PBS and the optical delay line 310. Based on this structure and connection, the first linearly polarized light R1, after being split by the first beam splitter 112, is transmitted to the PBS via the polarization transmission element 211. The PBS outputs the first linearly polarized light R1 to the quarter-wave plate, which converts the first linearly polarized light R1 into first circularly polarized light and outputs it to the optical delay line 310. The first circularly polarized light becomes second circularly polarized light after passing through the optical delay line 310 and the first reflection element 411, and then returns to the quarter-wave plate via the optical delay line 310. The quarter-wave plate converts the second circularly polarized light into the second linearly polarized light R1” and outputs it to the PBS. The PBS outputs the second linearly polarized light R1” to the second reflector 412 and outputs the second linearly polarized light R1” reflected back from the second reflector 412 back to the quarter-wave plate. The quarter-wave plate converts the second linearly polarized light R1” into the third circularly polarized light and outputs it to the optical delay line 310. The third circularly polarized light becomes the fourth circularly polarized light after passing through the optical delay line 310 and the first reflector 411, and then returns to the quarter-wave plate after passing through the optical delay line 310. The quarter-wave plate converts the fourth circularly polarized light’ into the third linearly polarized light R1”” and outputs it to the PBS. The PBS outputs the third linearly polarized light R1”” to the polarization light transmission element 211, and then transmits it to the mixer 114.

[0133] In the above signal transmission process, the linear polarization state of the first linearly polarized light R1 is the same as that of the third linearly polarized light R1””, and orthogonal to the linear polarization state of the second linearly polarized light R1””. For example, the first linearly polarized light R1 and the third linearly polarized light R1”” are both P-light or TE-light, and the second linearly polarized light R1”” is S-light or TM-light; or, the first linearly polarized light R1 and the third linearly polarized light R1”” are both S-light or TM-light, and the second linearly polarized light R1”” is P-light or TE-light. The first circularly polarized light and the fourth circularly polarized light have the same circular polarization state, and the second circularly polarized light and the third circularly polarized light have the same circular polarization state. For example, the first circularly polarized light and the fourth circularly polarized light both have the first circular polarization state, and the second circularly polarized light and the third circularly polarized light both have the second circular polarization state.

[0134] Therefore, there are many possible structures that can achieve the above-mentioned PBS functions. For example, in one example, as shown in Figures 9a and 9b, the PBS has a first end (f1), a second end (f2), and a third end (f3). P-light or TE-light is transmitted between the first end f1 and the second end f2, and S-light or TM-light is reflected between the second end f2 and the third end f3. Based on this:

[0135] When the first linearly polarized light R1 is P-light or TE-light, and the second linearly polarized light R1" is S-light or TM-light, as shown in Figure 9a, the first end f1 of the PBS is connected to the second end e2 of the polarization transmission element 211, the second end f2 of the PBS is connected to the first end of the quarter-wave plate, the second end of the quarter-wave plate is connected to the first end a1 of the optical delay line 310, and the third end f3 of the PBS is connected to the second reflection element 412. Furthermore, the positional relationship between the PBS and the quarter-wave plate is configured such that the optical signal output from the second end f2 of the PBS is incident on the quarter-wave plate at a 45° angle, and the quarter-wave plate can... It can be left-handed or right-handed, without limitation. Based on this design, the P-beam split by the first beam splitter 112 enters the first end e1 of the optical transmission element 211 and exits from the second end e2 of the optical transmission element 211, entering the first end f1 of the PBS. The PBS transmits the P-beam input from the first end f1 to the second end f2 of the PBS, so that the P-beam is incident at a 45° angle from the second end f2 onto the first end of the quarter-wave plate. The second end of the quarter-wave plate outputs light in the first circularly polarized state, which becomes the second circularly polarized light after passing through the optical delay line 310 and the first reflecting element 411. The light in the second circularly polarized state then passes through the optical delay line 310 and returns to the second end of the quarter-wave plate. The quarter-wave plate converts the light in the second circularly polarized state into S-beams and outputs them to the second end f2 of the PBS. The PBS reflects the S-beams input at the second end f2 to the third end f3 of the PBS, causing the S-beams to enter the second reflective element 412 from the third end f3 and be reflected back to the third end f3 of the PBS. The PBS reflects the S-beams input at the third end f3 to the second end f2 of the PBS, causing the S-beams to enter the first end of the quarter-wave plate at a 45° angle from the second end f2. The quarter-wave plate's... The second end outputs light in a second circularly polarized state. This light, after passing through the optical delay line 310 and the first reflecting element 411, becomes light in a first circularly polarized state. It then returns to the second end of the quarter-wave plate after passing through the optical delay line 310. The quarter-wave plate converts the first circularly polarized light into P-beams and outputs them to the second end f2 of the PBS. The PBS transmits the P-beams input at the second end f2 to the first end f1 of the PBS, causing the P-beams to enter the second end e2 of the polarization transmission element 211 from the first end f1, and then output from the third end e3 of the polarization transmission element 211, entering the mixer 114.

[0136] When the first linearly polarized light R1 is S-light or TM-light, and the second linearly polarized light R1" is P-light or TE-light, as shown in Figure 9b, the first end f1 of the PBS is connected to the second reflective element 412, the second end f2 of the PBS is connected to the first end of the quarter-wave plate, the second end of the quarter-wave plate is connected to the first end a1 of the optical delay line 310, and the third end f3 of the PBS is connected to the second end e2 of the polarization transmission element 211. Furthermore, the positional relationship between the PBS and the quarter-wave plate is configured such that the optical signal output from the second end f2 of the PBS is incident on the quarter-wave plate at a 45° angle. The quarter-wave plate can be a left-right... The polarization can be either right-handed or left-handed, without limitation. Based on this design, the S-beam split by the first beam splitter 112 enters the first end e1 of the optical transmission element 211 and exits from the second end e2 of the optical transmission element 211, entering the third end f3 of the PBS. The PBS reflects the S-beam input from the third end f3 back to the second end f2 of the PBS, so that the S-beam is incident at a 45° angle from the second end f2 onto the first end of the quarter-wave plate. The second end of the quarter-wave plate outputs light in the first circularly polarized state, which, after passing through the optical delay line 310 and the first reflecting element 411, becomes light in the second circularly polarized state. The light then passes through optical delay line 310 and returns to the second end of the quarter-wave plate. The quarter-wave plate converts the light in the second circularly polarized state into P-light and outputs it to the second end f2 of the PBS. The PBS transmits the P-light input at the second end f2 to the first end f1 of the PBS, so that the P-light enters the second reflective element 412 from the first end f1 of the PBS and is reflected back to the first end f1 of the PBS by the second reflective element 412. The PBS transmits the P-light input at the first end f1 to the second end f2 of the PBS, so that the P-light is incident at a 45° angle from the second end f2 to the first end of the quarter-wave plate. The second end of the quarter-wave plate... The output of the second circularly polarized light is converted to the first circularly polarized light after passing through the optical delay line 310 and the first reflecting element 411. This second circularly polarized light then returns to the second end of the quarter-wave plate after passing through the optical delay line 310. The quarter-wave plate converts the first circularly polarized light into S-beams and outputs them to the second end f2 of the PBS. The PBS reflects the S-beams input at the second end f2 to the third end f3 of the PBS, causing the S-beams to enter the second end e2 of the polarization transmission element 211 from the third end f3, and then output from the third end e3 of the polarization transmission element 211, entering the mixer 114.

[0137] Optionally, there are many implementations of the above PBS, including chip-integrated PBS and non-chip-integrated PBS.

[0138] For example, please refer to Figure 10a, which shows a schematic diagram of a PBS structure provided in Implementation Scheme 1. This structure is a non-chip integrated PBS, specifically a polarizing beam splitter prism. As shown in Figure 10a, this PBS is an optical element that utilizes the property that the P-polarized component is completely transmitted while the S-polarized component is reflected (at least 90%) after the beam passes through the multilayer film structure multiple times at the Brewster angle. For example, the PBS can separate the incident light (P-beam and S-beam) at the second end f2 into horizontally polarized light and vertically polarized light, i.e., P-beam and S-beam. The P-beam passes completely through and exits from the first end f1, while the S-beam is reflected at a 45° angle and exits from the third end f3, with the exit direction of the S-beam forming a 90° angle with the exit direction of the P-beam. Furthermore, the PBS can also allow the incident light (P-beam) at the first end f1 to pass completely through, reflect the incident light (S-beam) at the third end f3 at a 45° angle, with the exit direction of the S-beam being the same as that of the P-beam. The S-beam and P-beam are then combined into a single beam and exit from the second end f2.

[0139] For example, please refer to Figure 10b, which shows a schematic diagram of another PBS structure provided in Implementation Scheme 1. This structure is also a non-chip integrated PBS. The PBS consists of two parts: a first part at the top and a second part at the bottom. The surface in contact between the first part and the second part is a reflective surface. If horizontally polarized light and vertically polarized light, i.e., P-light and S-light, are input from the upper left of the first part (corresponding to the second end f2), the S-light will be reflected by the reflective surface to the upper right of the first part (corresponding to the third end f3), while the P-light will pass through the reflective surface into the second part. After transmission in the second part, it will exit from the lower right of the second part (corresponding to the first end f1). Conversely, if P-beam is input from the lower right of the second part (i.e., the first end f1) and S-beam is input from the upper right of the first part (i.e., the third end f3), then P-beam will pass through the reflecting surface into the first part and exit from the upper left of the first part (i.e., the second end f2). S-beam will be reflected by the reflecting surface and also exit from the upper left of the first part (i.e., the second end f2). S-beam and P-beam will combine into one beam and exit from the second end f2.

[0140] For example, please refer to Figure 10c, which shows a schematic diagram of another PBS structure provided in Implementation Scheme 1. This structure belongs to a chip-integrated PBS. In the chip-integrated PBS, the P-beam in Figures 9a and 9b can be replaced with the TE-beam, and the S-beam can be replaced with the TM-beam. Among them, Figure 10c (A) shows the external structure of the PBS, and Figure 10c (B) shows the internal structure of the PBS. Combining Figures 10c (A) and (B), the PBS includes a top oxide layer, a bottom buried oxide layer, and a waveguide structure wrapped between the two layers. The waveguide structure includes a straight waveguide and a curved waveguide, which are sandwiched between the top oxide layer and the bottom buried oxide layer. The top oxide layer and the bottom buried oxide layer are made of the same material, such as SiO2. The straight waveguide and the curved waveguide are of equal width and are partially parallel. The length of the parallel region needs to be carefully designed so that when the TM light is coupled from the straight waveguide to the curved waveguide, the TE light can hardly or only a small part of it can be coupled to the curved waveguide. It can be considered that the output of the curved waveguide is relatively pure TM light.

[0141] Based on the structure shown in Figure 10c, the end of the straight waveguide furthest from the curved waveguide is the first end f1 of the PBS, the end of the straight waveguide closest to the curved waveguide is the second end f2 of the PBS, and the end of the curved waveguide furthest from the straight waveguide is the third end f3 of the PBS. When TE and TM light are input to the f2 end of the straight waveguide, the TM light rapidly couples from the straight waveguide to the curved waveguide during transmission, while the TE light couples very little or almost nothing. Therefore, the light output from the f1 end of the straight waveguide is entirely TE light, and the light output from the f3 end of the curved waveguide is almost entirely TM light. Even if it is a mixture of TM and TE light, since the TE light is very small, it can be considered relatively pure TM light. Conversely, when TM light is input to the f3 end of the curved waveguide, the TM light rapidly couples from the curved waveguide to the straight waveguide during transmission, and the polarization direction of the TM light does not change during coupling. Therefore, the light output from the f2 end of the straight waveguide is still TM light. When TE light is input to the f1 end of the linear waveguide, the TE light will be transmitted from the f1 end of the linear waveguide to the f2 end of the linear waveguide. The polarization direction does not change during the transmission process. Therefore, the light output from the f2 end of the linear waveguide is still TE light.

[0142] In one example, considering that a small amount of TE light may also couple into the curved waveguide when the TM light couples from the straight waveguide to the curved waveguide, the TM light output from the f3 end of the curved waveguide may contain a small amount of TE light. Therefore, to further improve the purity of the TM light output from the third end (f3) of the PBS, multiple structures as shown in Figure 10c can be cascaded. In this way, even if a small amount of TE light is mixed in the TM light and output from the f3 end of the curved waveguide of the first structure, a very small portion of this TE light can couple into the curved waveguide of the next structure during the coupling process from the straight waveguide to the curved waveguide. Therefore, the TM light output from the f3 end of the curved waveguide of the next structure will be much purer than the TM light output from the f3 end of the curved waveguide of the first structure. Generally, cascading two structures is sufficient, effectively improving the purity of the TM light output from the PBS without significantly increasing structural complexity.

[0143] Based on the PBS structure shown in Figure 10c, since the PBS can be entirely located on the buried oxide layer (above the substrate), the PBS can be integrated into the chip. That is to say, using the above structure to implement the PBS not only enables the sharing of optical delay lines based on polarization multiplexing, but also achieves chip integration of the entire signal processing device, resulting in a high degree of integration.

[0144] However, it should be understood that PBS can also be implemented in other ways, such as through fiber optic devices, or through other polarization beam splitters, or through a chip-integratable structure different from that in Figure 10c, etc., without specific limitations here.

[0145] Based on the above implementation scheme one, the transmission of P-light or TE-light in the PBS, the reflection of S-light or TM-light in the PBS, and the conversion of light polarization by the 1 / 4 wave plate can be used to achieve four-fold multiplexing of the same optical delay line through one PBS, one 1 / 4 wave plate, and two reflective elements on the optical path. Therefore, under the same delay duration, the length of the optical delay line in the signal processing device can be shortened by 3 / 4. In this way, the length of the optical delay line required in the signal processing device can be greatly reduced, simplifying the architecture of the signal processing device and reducing the hardware cost of the signal processing device.

[0146] Implementation Plan 2

[0147] Please refer to Figure 11, which shows a schematic diagram of a signal processing device provided in Embodiment 2. In this example, the polarization adjustment element 212 includes a PSR and a quarter-wave plate. The PSR is connected between the polarization transmission element 211, the quarter-wave plate, and the second reflection element 412. The quarter-wave plate is connected between the PSR and the optical delay line 310. Based on this structure and connection, the first linearly polarized light R1 after being split by the first beam splitter 112 is transmitted to the PSR via the polarization transmission element 211. The PSR outputs the first linearly polarized light R1 to the quarter-wave plate, which converts the first linearly polarized light R1 into first circularly polarized light and outputs it to the optical delay line 310. The first circularly polarized light becomes second circularly polarized light after passing through the optical delay line 310 and the first reflection element 411, and then returns to the quarter-wave plate via the optical delay line 310. The quarter-wave plate converts the second circularly polarized light into fourth linearly polarized light R1. 10 ", and output to PSR. PSR will output the fourth linearly polarized light R 10 The light is converted into second linearly polarized light R1 and output to the second reflective element 412, and the second linearly polarized light R1 reflected back from the second reflective element 412 is converted into fourth linearly polarized light R 10 ", and then output it again to the quarter-wave plate. The quarter-wave plate will then output the fourth linearly polarized light R 10 The light is converted into third circularly polarized light and output to optical delay line 310. After passing through optical delay line 310 and the first reflector 411, the third circularly polarized light becomes fourth circularly polarized light, and then returns to the quarter-wave plate after passing through optical delay line 310. The quarter-wave plate converts the fourth circularly polarized light into third linearly polarized light R1”” and outputs it to PSR. PSR outputs the third linearly polarized light R1”” to polarization transmission element 211, and then transmits it to mixer 114.

[0148] In the above signal transmission process, the linear polarization state of the first linearly polarized light R1 is the same as that of the second linearly polarized light R1” and the third linearly polarized light R1””, and is also the same as that of the fourth linearly polarized light R 10 The linear polarization states are orthogonal. For example, the first linearly polarized light R1, the second linearly polarized light R1”, and the third linearly polarized light R1”” are all P-light or TE-light, and the fourth linearly polarized light R 10 "This refers to either S-polarized light or TM-polarized light. The first and fourth circularly polarized lights have the same circular polarization state, and the second and third circularly polarized lights have the same circular polarization state. For example, the first and fourth circularly polarized lights are both in the first circular polarization state, and the second and third circularly polarized lights are both in the second circular polarization state."

[0149] Based on this, there are many possible structures that can achieve the above PSR function. For example, as shown in Figure 12, the PSR has a first end (g1), a second end (g2), and a third end (g3). The first end g1 and the second end g2 transmit P-light or TE light in the original polarization direction, and the second end g2 and the third end g3 transmit signals in the polarization direction after a 90° rotation. For example, the P-light or TE light can be converted into S-light or TM-light and then output, and the returned S-light or TM-light can be converted into P-light or TE-light and then output. When the first linearly polarized light R1 is a P-light or TE-light, and the second linearly polarized light R1” is an S-light or TM-light, as shown in Figure 12, the first end g1 of the PSR is connected to the second end e2 of the polarization transmission element 211, the second end g2 of the PSR is connected to the first end of the quarter-wave plate, the second end of the quarter-wave plate is connected to the first end a1 of the optical delay line 310, and the third end g3 of the PSR is connected to the second reflection element 412. Furthermore, the positional relationship between the PSR and the quarter-wave plate is configured such that the optical signal output from the second end g2 of the PSR is incident on the quarter-wave plate at a 45° angle. The quarter-wave plate can be left-handed or right-handed, without limitation.

[0150] Based on this design, the P-beam split by the first beam splitter 112 enters the first end e1 of the optical transmission element 211 and exits from the second end e2, entering the first end g1 of the PSR. The PSR maintains the polarization direction of the P-beam input at the first end g1 and outputs it from the second end g2, so that the P-beam is incident at a 45° angle on the first end of the quarter-wave plate. The second end of the quarter-wave plate outputs light in a first circularly polarized state. After passing through the optical delay line 310 and the first reflector 411, the first circularly polarized light becomes light in a second circularly polarized state, and then returns to the second end of the quarter-wave plate after passing through the optical delay line 310. The quarter-wave plate converts the second circularly polarized light into S-beam and outputs it to the second end g2 of the PSR. The PSR rotates the polarization direction of the S-beam input at the second end g2 by 90°, converting it into P-beam, and outputs it from the third end g3 of the PSR, so that the P-beam enters the second reflector 412 and is reflected back to the third end g3 of the PSR. The PSR rotates the polarization direction of the P-beam input at its third terminal g3 by 90°, converting it into an S-beam, and outputs it from its second terminal g2, causing the S-beam to be incident at a 45° angle onto the first terminal of the quarter-wave plate. The second terminal of the quarter-wave plate outputs light in a second circularly polarized state. This light, after passing through the optical delay line 310 and the first reflecting element 411, becomes light in a first circularly polarized state, and then returns to the second terminal of the quarter-wave plate after passing through the optical delay line 310. The quarter-wave plate converts the first circularly polarized light back into a P-beam and outputs it to the second terminal g2 of the PSR. The PSR maintains the polarization direction of the P-beam input at its second terminal g2 and outputs it from its first terminal g1, causing the P-beam to enter the second terminal e2 of the polarization transmission element 211, and then output from the third terminal e3 of the polarization transmission element 211, entering the mixer 114.

[0151] Optionally, there are many ways to implement the above PSR, including chip-integrated PSR and non-chip-integrated PSR.

[0152] For example, please refer to Figure 13, which shows a schematic diagram of a PSR structure provided in Implementation Scheme 2. This structure belongs to a chip-integrated PSR. In the chip-integrated PSR, the P-beam in Figure 12 can be replaced with the TE-beam, and the S-beam can be replaced with the TM-beam. As shown in Figure 13, the PSR includes a straight waveguide and a curved waveguide. The straight waveguide and the curved waveguide are similar to the straight waveguide and the curved waveguide in the PBS shown in Figure 10c, but there are some differences, mainly including the following two points: 1. The widths of the straight waveguide and the curved waveguide are different. For example, the straight waveguide is wider, while the curved waveguide is relatively narrower; 2. The upper and lower sides of the straight waveguide and the curved waveguide need to be made of different materials. For example, if the bottom is made of a buried oxide layer composed of SiO2, then the top must be a non-SiO2 material. For example, it can be directly exposed to the air, or it can be covered by a layer composed of other materials, without limitation.

[0153] Based on the structure shown in Figure 13, the end of the straight waveguide furthest from the curved waveguide is the first end g1 of the PSR, the end of the straight waveguide closest to the curved waveguide is the second end g2 of the PSR, and the end of the curved waveguide furthest from the straight waveguide is the third end g3 of the PSR. When TE light is input to the g1 end of the straight waveguide, it will propagate from the g1 end to the g2 end of the straight waveguide. The polarization direction does not change during propagation; therefore, the light output from the g2 end of the straight waveguide is still TE light. When TE light is input to the g3 end of the curved waveguide, it will gradually couple from the curved waveguide to the straight waveguide during propagation. During coupling, the polarization direction of the TE light rotates by 90°, and the TE light becomes TM light. Therefore, the light output from the g2 end of the straight waveguide is TM light. Conversely, when TE light is input to the g2 end of the straight waveguide, it propagates from the g2 end to the g1 end along the straight waveguide without changing its polarization direction. Therefore, the light output from the g1 end of the straight waveguide is still TE light. When TM light is input to the g2 end of the straight waveguide, it gradually couples from the straight waveguide to the curved waveguide during propagation. During coupling, the polarization direction of the TM light rotates by 90°, transforming it into TE light. Therefore, the light output from the g3 end of the curved waveguide is TE light.

[0154] Based on the PSR structure shown in Figure 13, since the PSR can be entirely located on the buried oxide layer (above the substrate), the PSR can be integrated into the chip. In other words, using this structure to implement the PSR not only allows for the sharing of optical delay lines based on polarization multiplexing, but also enables the chip integration of the entire signal processing device, resulting in a high degree of integration.

[0155] However, it should be understood that PSR can also be implemented in other ways, such as through fiber optic devices, or through devices such as prisms combined with waveplates, or through a chip-integratable structure different from that shown in Figure 13, and so on. For example, in another example, the top and bottom sides of the straight waveguide and the curved waveguide in Figure 13 can be made of the same material, but the straight waveguide and the curved waveguide can be made into asymmetrical waveguides, such as ridge waveguides, which can also achieve the function of PSR. There are many other possible implementations, which will not be listed here.

[0156] Based on the above implementation scheme 2, the characteristics of PSR in transmitting P-light and S-light separately and converting P-light to S-light, or in transmitting TM-light and TE-light separately and converting TE-light to TM-light, as well as the polarization conversion of light by 1 / 4 wave plate, can be utilized to achieve four-fold multiplexing of the same optical delay line through one PSR, 1 / 4 wave plate and two reflective elements on the optical path. Under the same delay duration, the length of the optical delay line in the signal processing device can be shortened by 3 / 4, which can greatly reduce the length of the optical delay line required in the signal processing device, simplify the architecture of the signal processing device, and reduce the hardware cost of the signal processing device.

[0157] Implementation Plan 3

[0158] Please refer to Figure 14, which shows a schematic diagram of a signal processing device provided in Embodiment 3. This structure is similar to that in Embodiment 2; the polarization adjustment element 212 also includes a PSR and a quarter-wave plate, but the function of the PSR differs from that in Embodiment 2. Specifically:

[0159] In Scheme 3, after the PSR receives the first linearly polarized light R1 from the polarization transmission element 211, it converts the first linearly polarized light R1 into the fifth linearly polarized light R 11 The signal is then output to a quarter-wave plate. The quarter-wave plate directs the fifth linearly polarized light R... 11 The light is converted into first circularly polarized light and output to optical delay line 310. After passing through optical delay line 310 and first reflector 411, the first circularly polarized light becomes second circularly polarized light, then returns to the quarter-wave plate after passing through first reflector 411. The quarter-wave plate converts the second circularly polarized light into second linearly polarized light R1” and outputs it to PSR. PSR outputs the second linearly polarized light R1” to second reflector 412, and outputs the second linearly polarized light R1” reflected back from second reflector 412 back to the quarter-wave plate. The quarter-wave plate converts the second linearly polarized light R1” into third circularly polarized light and outputs it to optical delay line 310. After passing through optical delay line 310 and first reflector 411, the third circularly polarized light becomes fourth circularly polarized light, then returns to the quarter-wave plate after passing through first reflector 411. The quarter-wave plate converts the fourth circularly polarized light into sixth linearly polarized light R… 12", and output to PSR, PSR will convert the sixth linearly polarized light R 12 The light is converted into third linearly polarized light R1 and transmitted to polarization transmission element 211, and then transmitted to mixer 114 through polarization transmission element 211.

[0160] In the above signal transmission process, the linear polarization state of the first linearly polarized light R1 is the same as that of the second linearly polarized light R1” and the third linearly polarized light R1””, and is also the same as that of the fifth linearly polarized light R 11 The linear polarization state and the sixth linearly polarized light R 12 The linear polarization states are orthogonal. For example, the first linearly polarized light R1, the second linearly polarized light R1”, and the third linearly polarized light R1”” are all P-light or TE-light, and the fifth linearly polarized light R 11 and the sixth linearly polarized light R 12 "This refers to either S-polarized light or TM-polarized light. The first and fourth circularly polarized lights have the same circular polarization state, and the second and third circularly polarized lights have the same circular polarization state. For example, the first and fourth circularly polarized lights are both in the first circular polarization state, and the second and third circularly polarized lights are both in the second circular polarization state."

[0161] Similar to Scheme 2 above, as shown in Figure 15, the PSR in Scheme 3 also has a first end g1, a second end g2, and a third end g3. The first end g1 and the second end g2 transmit P-light or TE light in their original polarization direction, while the second end g2 and the third end g3 transmit signals in a polarization direction after a 90° rotation. The difference is that in Scheme 3, the first end g1 of the PSR is connected to the second reflector 412, and the third end g3 of the PSR is connected to the second end e2 of the polarization transmission element 211. Other connections are consistent with those in Scheme 2. Based on this design, the P-light split by the first beam splitter 112 enters the first end e1 of the light transmission element 211 and exits from the second end e2, entering the third end g3 of the PSR. The PSR rotates the polarization direction of the P-light input to the third end g3 by 90°, transforming it into S-light, and outputs it from the second end g2 of the PSR, causing the S-light to be incident at a 45° angle onto the first end of the quarter-wave plate. The second end of the quarter-wave plate outputs light in a first circularly polarized state. This light, after passing through the optical delay line 310 and the first reflecting element 411, becomes light in a second circularly polarized state, and then returns to the second end of the quarter-wave plate after passing through the optical delay line 310. The quarter-wave plate converts the second circularly polarized light into P-beams and outputs them to the second end g2 of the PSR. The PSR maintains the polarization direction of the P-beams input at the second end g2 and outputs them from the first end g1 of the PSR, causing the P-beams to enter the second reflecting element 412 and be reflected back to the first end g1 of the PSR. The PSR maintains the polarization direction of the P-beams input at the first end g1 and outputs them from the second end g2 of the PSR, causing the P-beams to be incident at a 45° angle on the first end of the quarter-wave plate. The second end of the quarter-wave plate outputs light in a second circularly polarized state. This light, after passing through the optical delay line 310 and the first reflecting element 411, becomes light in a first circularly polarized state, and then returns to the second end of the quarter-wave plate after passing through the optical delay line 310. A quarter-wave plate converts light in the first circularly polarized state into S-light and outputs it to the second terminal g2 of the PSR. The PSR rotates the polarization direction of the S-light input to the second terminal g2 by 90°, making it P-light, and outputs it from the third terminal g3 of the PSR. This P-light then enters the second terminal e2 of the polarization transmission element 211, and is output from the third terminal e3 of the polarization transmission element 211, entering the mixer 114.

[0162] It is understandable that there are many ways to implement the above PSR, including chip-integrated PSR and non-chip-integrated PSR. For example, it can be the structure shown in Figure 13 of the above implementation scheme 2, or it can be other structures, such as those implemented by optical fiber devices, or by devices such as prisms combined with waveplates, or by structures that can be integrated on a chip, which are different from those in Figure 13, etc., which will not be repeated here.

[0163] Based on the above implementation scheme 3, the characteristics of PSR in transmitting P-light and S-light separately and converting P-light to S-light, or in transmitting TM-light and TE-light separately and converting TE-light to TM-light, as well as the polarization conversion of light by 1 / 4 wave plate, can be utilized to achieve four-fold multiplexing of the same optical delay line through a PSR, 1 / 4 wave plate and two reflective elements on the optical path. Under the same delay duration, the length of the optical delay line in the signal processing device can be shortened by 3 / 4, which can greatly reduce the length of the optical delay line required in the signal processing device, simplify the architecture of the signal processing device, and reduce the hardware cost of the signal processing device.

[0164] It should be understood that the above content only illustrates several possible implementations of the polarization adjustment element 212, using the example that the first linearly polarized light and the second linearly polarized light have the same or orthogonal linear polarization states. In other examples, the first linearly polarized light and the second linearly polarized light may also have different but non-orthogonal linear polarization states. In this case, the structure of the polarization adjustment element 212 needs to be carefully designed so that the optical signal output by the polarization adjustment element 212 to the mixer 114 remains the same as the linear polarization state of the first linearly polarized light, while also delaying the first linearly polarized light four times. This application does not limit the specific structure of the polarization adjustment element 212.

[0165] The above content provides a detailed description of the structure and function of a frequency-modulated photoelectric circuit in a signal processing device. In this application, the signal processing device may have only one frequency-modulated photoelectric circuit or multiple frequency-modulated photoelectric circuits. When multiple frequency-modulated photoelectric circuits are present, their structures may be the same or different.

[0166] For example, taking the structure of the frequency modulation photoelectric circuit 110 shown in FIG7 above as an example, the structure of a signal processing device with multiple frequency modulation photoelectric circuits will be described below through different implementation schemes. However, it should be understood that the same scheme can also be applied to the frequency modulation photoelectric circuit 110 shown in FIG4 to FIG9b, FIG11, FIG12, FIG14 and FIG15, and this application does not specifically limit it.

[0167] Implementation Plan 4

[0168] Please refer to Figure 16, which shows a schematic diagram of a signal processing device provided in Embodiment 4. In this example, the signal processing device includes N frequency-modulated photoelectric circuits, namely frequency-modulated photoelectric circuit 110, frequency-modulated photoelectric circuit 120, ..., frequency-modulated photoelectric circuit 1N0, where N is an integer greater than or equal to 2. The structures of the N frequency-modulated photoelectric circuits are all identical, and the structure of each frequency-modulated photoelectric circuit can be seen in Figures 4 to 9b, 11, 12, 14, and 15 above.

[0169] For example, Figure 16 uses the structure shown in Figure 7 as an example. The frequency-modulated photoelectric circuit 110 includes the light source 111, the first beam splitter 112, the polarization light transmission element 211, the polarization light adjustment element 212, the optical delay line 310, the first reflection element 411, the second reflection element 412, the mixer 114, the photodetector 115, the amplifier 118, the analog-to-digital converter 119, the processing element 116, the drive circuit 117, and the target measurement path 113, as described above. Similarly, the frequency-modulated photoelectric circuit 120 includes the light source 121, the first beam splitter 122, the polarization light transmission element 221, the polarization light adjustment element 222, the optical delay line 320, the first reflection element 421, the first reflection element 422, the mixer 124, the photodetector 125, the amplifier 128, the analog-to-digital converter 129, the processing element 126, the drive circuit 127, and the target measurement path 123. ... The frequency modulation optoelectronic circuit 1N0 includes a light source 1N1, a first beam splitter 1N2, a polarization light transmission element 2N1, a polarization light adjustment element 2N2, an optical delay line 3N0, a first reflection element 4N1, a first reflection element 4N2, a mixer 1N4, a photodetector 1N5, an amplifier 1N8, an analog-to-digital converter 1N9, a processing element 1N6, a drive circuit 1N7, and a target measurement path 1N3.

[0170] Using the structure described in Implementation Scheme 1, the N frequency-modulated optoelectronic circuits have identical structures. Since the physical length of the optical delay line in each frequency-modulated optoelectronic circuit can be shortened by 3 / 4, the total length of the optical delay lines in the N frequency-modulated optoelectronic circuits can be shortened by 3 / 4 without reducing the delay time of the optical signal in the N frequency-modulated optoelectronic circuits. This reduces the space occupied by the optical delay lines in the N frequency-modulated optoelectronic circuits, thereby simplifying the architecture of the N frequency-modulated optoelectronic circuits and reducing costs.

[0171] Implementation Plan 5

[0172] Please refer to Figure 17, which shows a schematic diagram of a signal processing device provided in Embodiment 5. In this example, the signal processing device includes N frequency-modulated photoelectric circuits 110 to 1N0, where N is an integer greater than or equal to 2. The N frequency-modulated photoelectric circuits 110 to 1N0 share the same polarization processing element 210, optical delay line 310, first reflective element 411, and second reflective element 412. For example, they share the same polarization light transmission element 211, the same polarization light adjustment element 212, the same optical delay line 310, the same first reflective element 411, and the same second reflective element 412.

[0173] In implementation scheme five, apart from the polarization processing element 210, optical delay line 310, first reflective element 411, and second reflective element 412 being shared, the other components described above can be individually configured in the N frequency-modulated photoelectric circuits 110 to 1N0. For example, as shown in Figure 17, frequency-modulated photoelectric circuit 110 includes the light source 111, first beam splitter 112, mixer 114, photodetector 115, amplifier 118, analog-to-digital converter 119, processing element 116, drive circuit 117, and target measurement path 113 described above. Similarly, frequency-modulated photoelectric circuit 120 includes a light source 121, first beam splitter 122, mixer 124, photodetector 125, amplifier 128, analog-to-digital converter 129, processing element 126, drive circuit 127, and target measurement path 123. ... The frequency modulation optoelectronic circuit 1N0 includes a light source 1N1, a first beam splitter 1N2, a mixer 1N4, a photodetector 1N5, an amplifier 1N8, an analog-to-digital converter 1N9, a processing element 1N6, a drive circuit 1N7, and a target measurement path 1N3.

[0174] In addition to the components mentioned above, as shown in Figure 17, the signal processing device may also include a beam combining element 510 and a second beam splitting element 520. The beam combining element 510 has N input terminals, namely k1, k2, ..., k N The second beam splitter 520 has N output terminals, namely h1, h2, ..., h... N The N input terminals k1 to k2 of the optical combining element 510 N The first output terminals c of the N first beam splitting elements 112 to 1N2 of the N frequency-modulated photoelectric circuits 110 to 1N0 are connected in a one-to-one correspondence. 11 ~c N1 The second output terminal c of the N first beam splitting elements 112 to 1N2 of the N frequency-modulated optoelectronic circuits 110 to 1N0 12 ~c N2 The second input terminals d of N mixers 114 to 1N4, which are respectively connected to N frequency modulation optoelectronic circuits 110 to 1N0, are respectively connected to the N frequency modulation optoelectronic circuits 110 to 1N0. 12 ~d N2 The third output terminal c of N frequency-modulated optoelectronic circuits 110~1N0 and N first beam-splitting elements 112~1N2 13 ~c N3 N target measurement paths 103 to 1N3 are respectively connected to N frequency-modulated photoelectric circuits 110 to 1N0. A polarization processing element 210 is connected between the output of the beam combiner 510 and the input of the second beam splitter 520. For example, the output of the beam combiner 510 is connected to the first end e1 of the polarization transmission element 211, and the third end e3 of the polarization transmission element 211 is connected to the input of the second beam splitter 520. The N outputs h1 to h2 of the second beam splitter 520 are...N The first input terminals d of N mixers 114 to 1N4, which are connected in a one-to-one correspondence to N frequency modulation optoelectronic circuits 110 to 1N0, are respectively connected to the N frequency modulation optoelectronic circuits. 11 ~d N1 .

[0175] Based on the above structure and connection relationship, in each frequency-modulated photoelectric circuit, the first beam splitter performs beam splitting processing on the beam generated by the light source to obtain the linearly polarized detection signal, the calibration path local oscillator signal and the light signal to be delayed. The first beam splitter inputs the detection signal to the target measurement path for target measurement through its third output terminal, inputs the calibration path local oscillator signal to the mixer through its second output terminal, and inputs the light signal to be delayed to the beam combining element 510 through its first output terminal.

[0176] Furthermore, the optical combining element 510 connects to its N input terminals k1 to k2. N Receive the N linearly polarized optical signals R1 to R2 output from the N first beam splitters 112 to 1N2 in N frequency-modulated optoelectronic circuits 110 to 1N0. N For the delayed optical signals R1 to R2 in N linearly polarized states... N The beam is combined to obtain the total first linearly polarized light R0, which is then input to the first end e1 of the polarization light transmission element 211. The total first linearly polarized light R0 is output from the second end e2 of the polarization light transmission element 211 and transmitted to the polarization light adjustment element 212. The polarization light adjustment element 212 converts the total first linearly polarized light R0 into total first circularly polarized light and outputs it to the optical delay line 310. The total first circularly polarized light passes through the optical delay line 310, the first reflection element 411, and the optical delay line 310 before returning to the polarization light adjustment element 212. The polarization light adjustment element 212 converts it into total second linearly polarized light R0” and outputs it to the second reflection element 412. The total second linearly polarized light R0” is reflected back to the polarization light adjustment element 212 by the second reflection element 412, and then converted into total third circularly polarized light by the polarization light adjustment element 212 and output to the optical delay line 310. The total third circularly polarized light passes through the optical delay line 310, the first reflecting element 411, and the optical delay line 310 before returning to the polarization adjustment element 212. There, it is converted into the total third linearly polarized light R0”” and output to the second end e2 of the polarization transmission element 211. The total third linearly polarized light R0”” is output from the third end e3 of the polarization transmission element 211 and enters the second beam splitter 520.

[0177] Furthermore, the second beam splitter 520 performs beam splitting on the total third linearly polarized light R0””, obtaining N third linearly polarized lights R1””~R corresponding to N frequency-modulated photoelectric circuits 110~1N0. N ", and through its N output terminals h1 to h NN third linearly polarized beams R1””~R N The signals are sent to N mixers 114 to 1N4 in N frequency-modulated photoelectric circuits 110 to 1N0 respectively. In each frequency-modulated photoelectric circuit, the mixer mixes the local oscillator signal of the linear polarization calibration path input from the first beam splitter and the third linear polarization light input from the second beam splitter 520 to obtain an intermediate frequency signal. The intermediate frequency signal is detected by the photodetector and converted into an electrical signal. The electrical signal is amplified by the amplifier and output to the analog-to-digital converter. After being converted into a digital signal by the analog-to-digital converter, it is output to the processing element. The processing element obtains a feedback signal based on the digital signal and inputs the feedback signal into the drive circuit. The drive circuit generates a modulation signal based on the feedback signal and inputs the modulation signal into the light source to calibrate the linearity between the modulation signal and the beam output by the light source. This allows the light source to output a beam that conforms to a linear change law under the action of the modulation signal. After the beam is split and enters the target measurement path (i.e., the detection signal), the detection accuracy of the target measurement path can be improved.

[0178] In the above description, the beam combining element 510 can be any device or combination of devices with beam combining function, such as a beam combiner, an optical coupler, or a combination of beam combiners, or a combination of a beam combiner and an optical coupler, etc., without specific limitations. Taking a beam combiner as an example, the beam combiner can be any type of beam combiner, such as including but not limited to: wavelength-type beam combiners, power-type beam combiners, polarization-type beam combiners, or other types of beam combiners, etc. Similarly, the second beam splitting element 520 can be any device or combination of devices with beam splitting function, such as a beam splitter, a beam combiner / splitter, or a combination of beam splitters, or a combination of a beam splitter / beam combiner / splitter, etc., without specific limitations. Taking a beam splitter as an example, the beam splitter can include but is not limited to: wavelength-type beam splitters, power-type beam splitters, polarization-type beam splitters, or other types of beam splitters, etc.

[0179] Using the structure in Implementation Scheme 5, N frequency-modulated optoelectronic circuits share the same optical delay line. The presence of the polarization processing element and two reflective elements can shorten the physical length of the optical delay line by 3 / 4. Furthermore, the sharing of the same optical delay line among the N frequency-modulated optoelectronic circuits saves N-1 optical delay lines. Therefore, when the above signal processing device is applied to an FMCW LiDAR, the length of the optical delay line in the N frequency-modulated optoelectronic circuits can be only 1 / 4N of the length of the optical extension line in existing FMCW LiDARs, without reducing the delay time of the optical signal for the N frequency-modulated optoelectronic circuits. This achieves a minimalist architecture and extremely low cost for the FMCW LiDAR.

[0180] Understandably, 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 one another. The technical features of different implementation schemes can be combined to form new implementation schemes based on their inherent logical relationships.

[0181] For example, in one example, combining the above-described Scheme 1 and Scheme 5, Scheme 6 can be obtained, the structure of which and the form of polarization signal flow are shown in Figure 18a. In Scheme 6, N frequency-modulated optoelectronic circuits 110 to 1N0 share the same polarization light transmission element 211, polarization light adjustment element 212, optical delay line 310, first reflection element 411 and second reflection element 412, and the polarization light adjustment element 212 includes a PBS and a 1 / 4 wave plate.

[0182] Optionally, as shown in Figure 18a, if the light beams emitted by the N light sources 111 to 1N1 in the N frequency-modulated photoelectric circuits 110 to 1N0 are P-beams, then the signals to be delayed after being split by the N first beam splitters 112 to 1N2 in the N frequency-modulated photoelectric circuits 110 to 1N0 received by the beam combining element 510 are also P-beams. The beam combining element 510 combines the N P-beams into a total P-beam and sends it to the polarization transmission element 211. The total P-beam is transmitted to the quarter-wave plate after passing through the polarization transmission element 211 and the PBS, where it is converted into circularly polarized light. After passing through the optical delay line 310, the first reflection element 410, and the optical delay line 310 to complete two delays, it returns to the quarter-wave plate, is converted into S-beams by the quarter-wave plate, and is output to the PBS. Then, it is output by the PBS to the second reflection element 412 and reflected back to the PBS. Finally, it is transmitted by the PBS to the quarter-wave plate. A quarter-wave plate converts S-beams into circularly polarized light. This circularly polarized light undergoes two delays via optical delay line 310, first reflective element 410, and optical delay line 310 before returning to the quarter-wave plate. The quarter-wave plate converts this light into P-beams, which are then output to the polarization beam splitter (PBS). From there, the light is output to polarization transmission element 211 and transmitted to the second beam splitter 520. The second beam splitter 520 splits the P-beams into P-beams corresponding to N frequency-modulated photoelectric circuits 110–1N0, and outputs them to N mixers 114–1N4 of each of the N frequency-modulated photoelectric circuits 110–1N0. The delayed signal of the P-beam in each frequency-modulated photoelectric circuit is mixed with the local oscillator signal of the P-beam calibration path in its respective mixer to become an intermediate frequency signal, which participates in subsequent beam calibration operations.

[0183] Optionally, as shown in Figure 18a, if the light beams emitted by the N light sources 111 to 1N1 in the N frequency-modulated photoelectric circuits 110 to 1N0 are S-beams, then the signals to be delayed after being split by the N first beam splitters 112 to 1N2 in the N frequency-modulated photoelectric circuits 110 to 1N0 received by the beam combining element 510 are also S-beams. The beam combining element 510 combines the N S-beams into a total S-beam and sends it to the polarization transmission element 211. The total S-beam is transmitted to the quarter-wave plate after passing through the polarization transmission element 211 and the PBS, where it is converted into circularly polarized light. After passing through the optical delay line 310, the first reflection element 410, and the optical delay line 310 to complete two delays, it returns to the quarter-wave plate, is converted into P-beams by the quarter-wave plate, and outputs to the PBS. It is then output to the second reflection element 412 via the PBS, reflected back to the PBS by the second reflection element 412, and transmitted to the quarter-wave plate by the PBS. A quarter-wave plate converts P-beams into circularly polarized light and outputs it to an optical delay line 310. After passing through the optical delay line 310, the first reflecting element 410, and the optical delay line 310 again for two delays, the P-beam returns to the quarter-wave plate, is converted into S-beams, and outputs to a PBS (polarizing photoelectric circuit). The PBS then outputs the S-beams to a polarization transmission element 211, which transmits them to a second beam splitter 520. The second beam splitter 520 splits the S-beams into S-beams corresponding to N frequency-modulated photoelectric circuits 110–1N0, and outputs them to N mixers 114–1N4 of each of the N frequency-modulated photoelectric circuits 110–1N0. The delayed signal of the S-beam in each frequency-modulated photoelectric circuit is mixed with the local oscillator signal of the S-beam calibration path in its respective mixer to become an intermediate frequency signal, which participates in subsequent beam calibration operations.

[0184] For example, in another example, combining the above-described Scheme 2 and Scheme 5, Scheme 7 can also be obtained, the structure of which and the form of polarization signal flow are shown in Figure 18b or Figure 18c. In Scheme 7, N frequency-modulated optoelectronic circuits 110 to 1N0 share the same polarization light transmission element 211, polarization light adjustment element 212, optical delay line 310, first reflection element 411 and second reflection element 412, and the polarization light adjustment element 212 includes a PSR and a 1 / 4 wave plate.

[0185] Optionally, if the PSR functions as shown in Figure 11 of the above-described embodiment two, then as shown in Figure 18b, the light beams emitted by the N light sources 111 to 1N1 in the N frequency-modulated photoelectric circuits 110 to 1N0 are P-beams. Therefore, the signals to be delayed after being split by the N first beam splitters 112 to 1N2 in the N frequency-modulated photoelectric circuits 110 to 1N0 received by the beam combining element 510 are also P-beams. The beam combining element 510 combines the N P-beams into a total P-beam and sends it to the polarization transmission element 211. The total P-beam is transmitted to the quarter-wave plate after passing through the polarization transmission element 211 and the PSR, and is converted into circularly polarized light by the quarter-wave plate. After passing through the optical delay line 310, the first reflection element 410, and the optical delay line 310 to complete two delays, it returns to the quarter-wave plate, is converted into S-beams by the quarter-wave plate and output to the PSR, and then is converted into P-beams by the PSR and output to the second reflection element 412. The P-beam is reflected back to the PSR by the second reflecting element 412, then converted into S-beam by the PSR and transmitted to the quarter-wave plate. The quarter-wave plate converts the S-beam into circularly polarized light, which undergoes two delays via the optical delay line 310, the first reflecting element 410, and the optical delay line 310 before returning to the quarter-wave plate. The quarter-wave plate converts the S-beam into P-beam, which is then output to the PSR. The PSR then outputs the P-beam to the polarization transmission element 211, and finally transmits it to the second beam splitter 520. The second beam splitter 520 splits the P-beam into P-beams corresponding to N frequency-modulated photoelectric circuits 110–1N0, and outputs them to N mixers 114–1N4 of the N frequency-modulated photoelectric circuits 110–1N0. The delayed signal of the P-beam in each frequency-modulated photoelectric circuit is mixed with the local oscillator signal of the P-beam calibration path in its respective mixer to become an intermediate frequency signal, which participates in subsequent beam calibration operations.

[0186] Optionally, if the function of the PSR is as shown in Figure 14 of the above-described second embodiment, then as shown in Figure 18c, the light beams emitted by the N light sources 111 to 1N1 in the N frequency-modulated photoelectric circuits 110 to 1N0 are P-beams. Therefore, the delay signals received by the light combining element 510 after being split by the N first beam splitting elements 112 to 1N2 in the N frequency-modulated photoelectric circuits 110 to 1N0 are also P-beams. The light combining element 510 combines the N P-beams into a total P-beam and sends it to the polarization light transmission element 211. The total P-beam is transmitted to the PSR via the polarization transmission element 211, where it is converted into S-beam and output to the quarter-wave plate. The quarter-wave plate converts the S-beam into circularly polarized light. This circularly polarized light undergoes two delays via the optical delay line 310, the first reflection element 410, and the optical delay line 310 before returning to the quarter-wave plate. It is then converted back into P-beam by the quarter-wave plate and output to the PSR. The PSR outputs the P-beam to the second reflection element 412. The P-beam is reflected back to the PSR by the second reflection element 412, and then output to the quarter-wave plate. It is converted back into circularly polarized light by the quarter-wave plate. This circularly polarized light undergoes two delays via the optical delay line 310, the first reflection element 410, and the optical delay line 310 before returning to the quarter-wave plate. It is then converted back into S-beam by the quarter-wave plate and output to the PSR. The PSR converts it back into P-beam and outputs it to the polarization transmission element 211, where it is then transmitted to the second beam splitter 520. The second beam splitter 520 splits the P-beam into P-beams corresponding to N frequency-modulated optoelectronic circuits 110 to 1N0, and outputs them to N mixers 114 to 1N4 of the N frequency-modulated optoelectronic circuits 110 to 1N0 respectively. The delayed signal of the P-beam in each frequency-modulated optoelectronic circuit is mixed with the local oscillator signal of the calibration path of the P-beam in its respective mixer to become an intermediate frequency signal, which participates in the subsequent beam calibration operation.

[0187] Understandably, there are other implementation plans, which will not be listed here.

[0188] It should be noted that in the above-described embodiments four to seven, the N signals to be delayed corresponding to the N frequency-modulated photoelectric circuits 110 to 1N0 need to be combined into one path and then split into multiple paths. Therefore, in order to achieve the accuracy of beam splitting, the N signals to be delayed need to have wavelength differences. For example, the N optical signals output by the N light sources 111 to 1N1 in the N frequency-modulated photoelectric circuits 110 to 1N0 can be optical signals of different wavelengths. These optical signals of different wavelengths are split into linearly polarized light of different wavelengths by the N first beam splitting elements 112 to 1N2, and then combined into one multi-wavelength optical signal by the first beam combining element 510. This multi-wavelength optical signal is then subjected to four delay processing by the optical delay line 310, and then split into N delayed optical signals by the second beam splitting element 520. The N delayed optical signals enter their respective mixers and are mixed with the local oscillator signal of the calibration path corresponding to the wavelength.

[0189] The second beam splitter 520 can be based on wavelength, power, or resonance, and the specific method is not limited. For example, when based on wavelength, the second beam splitter 520 can separate pure, time-delayed optical signals of different wavelengths. These time-delayed optical signals of different wavelengths are output to their respective mixers and mixed with the local oscillator signal of the calibration path of the same wavelength. When based on power or resonance, although the second beam splitter 520 may separate time-delayed optical signals with multiple wavelengths in each path (e.g., each time-delayed optical signal is a uniformly mixed optical signal of various wavelengths), during mixing in the mixer, the wavelength of the calibration path local oscillator signal is used for mixing, and other wavelengths are not used. Therefore, power or resonance beam splitting can also achieve subsequent mixing and processing functions.

[0190] Furthermore, the above-described implementation schemes four to seven all use the example of N frequency-modulated photoelectric circuits 110 to 1N0 having their own separate target measurement paths. This is only one possible example. In other examples, the N frequency-modulated photoelectric circuits 110 to 1N0 may also share the same target measurement path, or some of the frequency-modulated photoelectric circuits may share the same target measurement path, while the other frequency-modulated photoelectric circuits have their own separate target measurement paths.

[0191] For example, taking the N frequency-modulated photoelectric circuits shown in Figure 17 as an example, please refer to Figure 19, which shows a scheme in which N frequency-modulated photoelectric circuits share the same target measurement path 113. In the case of sharing, the third beam splitter 1131 in the target measurement path 113 shown in Figure 6 can be replaced by an optical processing 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 optical processing element 1138 has N input terminals and two output terminals. The N input terminals are connected one-to-one to the third output terminals c of the first beam splitter 112 to 1N2 in the N frequency-modulated photoelectric circuits 110 to 1N0. 13 ~c N3 One output terminal is connected to the first terminal b of the polarization light transmission element 1132. 51Another output terminal is connected to one input terminal of mixer 1133. Based on this structure and connection, optical processing element 1138 can receive N detection signals obtained by the first beam splitting elements 112 to 1N2 of N frequency-modulated photoelectric circuits 110 to 1N0 through its N input terminals. Optical processing element 1138 combines these N 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 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 N 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.

[0192] It is understood that the above implementation schemes are merely illustrative examples of several possible implementations of transmitting two or more sets of optical signals in the same optical delay line using polarization processing elements. In actual signal processing devices, there may be other implementations. Any scheme that can reuse one optical delay line to transmit two or more sets of linearly polarized optical signals is within the scope of protection of this application, and this application does not make any specific limitations on it.

[0193] The specific structure and function of each component shown in the above figures will be described below to provide an exemplary implementation scheme.

[0194] 1. Light source

[0195] 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.

[0196] 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 an FMCW LiDAR.

[0197] 2. Spectrometer

[0198] 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.

[0199] For example, taking the first beam splitter 112 in Figure 5 as an example (see Figure 20a), the first 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 first beam splitter 112, and the first output terminal (t) of the first beam splitter 1121... 11 ) Connect the input terminal of the second beam splitter 1122, and the second output terminal (t) of the first beam splitter 1121 12 The third output terminal c corresponding to the first beam splitter 112 13 The first output terminal (t) of the second beam splitter 1122 21 The first output terminal c of the first beam splitter 112 11 The second output terminal (t) of the second beam splitter 1122 22 The second output terminal c corresponding to the first beam splitter 112 12 That is to say, the input terminal of the first beam splitter 1121 is connected to the output terminal of the light source 111, and the second output terminal of the first beam splitter 1121 is connected to the output terminal of the light source 111. 12 Connect the target measurement path 113, and the first output terminal t of the second beam splitter 1122 21 Connect the first terminal e1 of the polarization transmission element 211 and the second output terminal t of the second beam splitter 1122. 22 Connect to the second input terminal d of mixer 114 12 .

[0200] Based on the above structure and connection, the linearly polarized light signal R output by the light source 111 enters the first beam splitter 1121. The first beam splitter 1121 performs beam splitting on the linearly polarized light signal R to obtain a linearly polarized detection signal and an intermediate light signal (R0). 13 The first beam splitter 1121 outputs through its second output terminal t. 12 The linearly polarized detection signal is output, allowing it to enter the target measurement path 113 and participate in target measurement. The first beam splitter 1121 also outputs a linearly polarized detection signal through its first output terminal t. 11 The intermediate optical signal R in the linearly polarized state of the output 13 This makes the intermediate optical signal R 13 The signal enters the second beam splitter 1122. The second beam splitter 1122 splits the linearly polarized intermediate optical signal R... 13 The beam is split to obtain the linearly polarized calibration path local oscillator signal and the delay signal R1. The second beam splitter 1122 outputs the signal through its second output terminal t. 22 The calibration path local oscillator signal in linear polarization is output, allowing it to directly enter mixer 114. The second beam splitter 1122 also outputs the signal through its first output terminal t. 21The output linearly polarized signal R1 (i.e., the first linearly polarized light) is delayed so that it passes sequentially through the polarization transmission element 211, the polarization adjustment element 212, the optical delay line 310, the first reflection element 411, the optical delay line 310, the polarization adjustment element 212, the second reflection element 412, the polarization adjustment element 212, and the polarization transmission element 211, completing four delays before entering the mixer 114.

[0201] 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.

[0202] 3. Polarization processing element

[0203] As described above, the polarization processing element 210 may include a polarization light transmission element 211 and a polarization light adjustment element 212.

[0204] Optionally, the polarization transmission element 211 can be any device with at least three ports and unidirectional transmission between the ports, such as the circulator shown in Figure 20a, an isolator, or a coupler. Although the coupler cannot completely transmit the optical signal R1”” after four delays to the mixer 114, 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 R1”” after four delays is transmitted to the mixer 114. Of course, the polarization transmission element 211 may also be other devices, which are not specifically limited here.

[0205] Optionally, the polarization adjustment element 212 may include a PBS and a quarter-wave plate, as shown in Figures 8, 9a, or 9b above, or a PSR and a quarter-wave plate, as shown in Figures 11, 12, 14, or 15 above. In some scenarios, it may also be a combination of PBS, PSR, and quarter-wave plate. For example, the PBS in Figure 8 above can be replaced with two PSRs. The two PSRs rotate the polarization direction of one of the input signals twice by 90° to restore the original polarization direction, thereby realizing the function of the PBS. There are many other possible implementations, which will not be repeated here.

[0206] 4. Optical Delay Line

[0207] An optical delay line is a component that delays the transmission of optical signals. Examples include, but are not limited to, fiber optic delay lines and integrated waveguide delay lines. Fiber optic delay lines utilize the propagation of optical signals within optical fibers to achieve signal delay and are typically quite long. Integrated waveguide delay lines, on the other hand, 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.

[0208] Understandably, when the optical delay line is a fiber optic delay line, shortening its length using polarization processing elements and two reflecting elements reduces its footprint in the signal processing device, thus lowering the hardware cost. Conversely, when the optical delay line is an integrated waveguide delay line, its footprint within the corresponding chip in the signal processing device can be reduced, thereby lowering chip costs and ultimately reducing the overall hardware cost of the signal processing device.

[0209] 5. Reflective element

[0210] Here, the reflective element includes the first reflective element and the second reflective element mentioned above. The reflective element can be any element capable of reflecting optical signals, including but not limited to: mirrors, fiber optic ring mirrors, Sagnac ring reflectors, or Bragg gratings.

[0211] For example, taking a Sagnac ring reflector as both the first and second reflecting elements as examples, referring to Figure 20a and Figure 7 above, the first reflecting element 411 can specifically include a fourth beam splitter 4111 and a first loop 4112. One end of the fourth beam splitter 4111 is connected to the second end a2 of the optical delay line 310, and the other two ends of the fourth beam splitter 4111 are connected together through optical fibers to form the first loop 4112. Similarly, the second reflecting element 412 can specifically include a fifth beam splitter 4121 and a second loop 4122. One end of the fifth beam splitter 4121 is connected to the third end j3 of the polarization adjustment element 212, and the other two ends of the fifth beam splitter 4121 are connected together through optical fibers to form the second loop 4122.

[0212] Based on this structure, the optical signal, after the initial delay by the optical delay line 310, enters the fourth beam splitter 4111. The fourth beam splitter 4111 splits the optical signal after the initial delay, resulting in two optical signals with equal intensity and phase. The two optical signals return to the fourth beam splitter 4111 along opposite directions through the first loop 4112. At this point, the intensity and phase of the two optical signals are still equal. The fourth beam splitter 4111 then acts as a beam combiner, combining the two optical signals. The combined optical signal returns to the delay line 310 along the original path for a second delay. Similarly, the optical signal after the second delay passes through the polarization adjustment element 212 and enters the fifth beam splitter 4121. The fifth beam splitter 4121 splits the optical signal after the second delay, resulting in two optical signals with equal intensity and phase. The two optical signals return to the fifth beam splitter 4121 via the second loop 4122 in opposite directions. At this time, the light intensity and phase of the two optical signals are still equal. The fifth beam splitter 4121 becomes a beam combiner and combines the two optical signals. The combined optical signal returns to the polarization adjustment element 212 along the original path. Then, it is output by the polarization adjustment element 212 to the optical delay line 310 for the third delay. After passing through the fourth beam splitter 4111 and the first loop 4112, it returns to the optical delay line 310 for the fourth delay. Finally, it enters the mixer 114 after passing through the polarization adjustment element 212 and the polarization transmission element 211.

[0213] 6. Mixer

[0214] In a frequency modulation optoelectronic circuit, the mixer can perform frequency mixing on the input signal and output an intermediate frequency signal.

[0215] 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, in one example, referring to Figure 20a and Figure 7 above, mixer 114 can be a 180° optical mixer with two output terminals d. 21 and d 22 It can coherently mix the local oscillator signal of the calibration path and the optical signal R1”” after four delays, so that the two output terminals d 21 and d 22 The relative phase differences of the output signals are 0° and 180°, respectively. For example, in another example, referring to Figure 20b and Figure 7 above, mixer 114 can be a 90° optical mixer with four output terminals d. 21 d 22 d 23 and d 24 It can coherently mix the local oscillator signal of the calibration path and the optical signal R1”” after four delays, so that the four output terminals d 21 d22 d 23 and d 24 The relative phase differences are 0°, 90°, 180°, and 270°, respectively. And so on, not all will be listed here.

[0216] 7. Optical detection element

[0217] 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).

[0218] Taking a PD as an example, the photodetector element may include at least one PD, and the number of at least one PD may be the same as the number of output terminals of the mixer placed in front of it. For example, referring to Figure 20a and Figure 7 above, when the mixer 114 is a 180° optical mixer, the photodetector element 115 may specifically include two PDs, namely PD1 and PD2, and the input terminal of PD1 is connected to one output terminal d of the 180° optical mixer. 21 Above, the input terminal of PD2 is connected to the other output terminal d of the 180° optical mixer. 22 The outputs of PD1 and PD2 are connected to the input of amplifier 118. PD1 and PD2 can be used to detect signals with a relative phase difference of 0° and 180° from the output of 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 Figure 20b and Figure 7 above, when mixer 114 is a 90° optical mixer, the optical detection element 115 can specifically include four PDs, namely PD11, PD12, PD21, and PD22. The inputs of PD11, PD12, PD21, and PD22 are respectively connected to the four outputs of the 90° optical mixer. 21 d 22 d 23 and d 24 The outputs of PD11, PD12, PD21, and PD22 are connected in pairs to the input of an amplifier. PD11, PD12, PD21, and PD22 can be used to probe the four outputs of a 90° optical mixer. 21 d 22 d 23 and d 24The output signals have relative phase differences of 0°, 90°, 180° and 270°, which are converted into electrical signals and then combined in pairs before being transmitted to the subsequent amplifier.

[0219] 8. Amplifier

[0220] 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).

[0221] 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, referring to Figure 20a and Figure 7 above, when the photodetector element 115 includes two PDs, namely PD1 and PD2, the amplifier 118 may include one TIA, namely TIA 1180. The output terminals of PD1 and PD2 are combined and connected to the input terminal of the TIA 1180. Therefore, the two intermediate frequency signals detected by PD1 and PD2 are combined into one and sent to the TIA 1180. The TIA 1180 can amplify the combined intermediate frequency signal with a certain intensity of low noise. For example, referring to Figure 20b and Figure 7 above, when the photodetector 115 includes four photodetectors (PDs), namely PD11, PD12, PD21, and PD22, the amplifier 118 can include two intermediate frequency amplifiers (TIAs), namely TIA 1181 and TIA 1182. The outputs of PD11 and PD12 are combined and connected to the input of TIA 1181, and the outputs of PD21 and PD22 are combined and connected to the input of TIA 1182. Therefore, the two intermediate frequency signals detected by PD11 and PD12 are combined into one and sent to TIA 1181 (referred to as the first intermediate frequency signal Z1), and the two intermediate frequency signals detected by PD21 and PD22 are combined into one and sent to TIA 1182 (referred to as the second intermediate frequency signal Z2). TIA 1181 and TIA 1182 respectively amplify the first intermediate frequency signal Z1 and the second intermediate frequency signal Z2 with a certain intensity of low noise.

[0222] 9. Analog-to-digital converter

[0223] 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.

[0224] 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 included in the amplifier preceding it. For example, referring to Figure 20a and Figure 7 above, 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 Z output by TIA 1180 to obtain a digital signal. For example, referring to Figure 20b and Figure 7 above, when amplifier 118 includes two TIAs, namely TIA 1181 and TIA 1182, analog-to-digital conversion 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 perform analog-to-digital conversion on the amplified first intermediate frequency signal Z1 output from TIA 1181 to obtain a first digital signal. ADC 1192 is used to perform analog-to-digital conversion on the amplified second intermediate frequency signal Z2 output from TIA 1182 to obtain a second digital signal. The first and second digital signals are input together to processing element 116.

[0225] 10. Processing Components

[0226] A processing element refers to a device with signal processing capabilities, such as a digital signal processor (DSP). Referring to Figures 7, 20a, or 20b above, the processing element 116 may specifically include a DSP 1160. The DSP 1160 can process one or more digital signals output from the analog-to-digital converter 119 to obtain a feedback signal P, which is then input to the drive circuit 117. This feedback signal can be used to calibrate the linearity between the modulation signal output from the drive 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 refers to calculating the frequency sweep curve by monitoring changes in the modulation signal and determining whether the frequency sweep 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 also possible, which are not specifically limited here.

[0227] 11. Drive circuit

[0228] The driving circuit can generate a modulation signal based on the feedback signal output from the processing element and input the modulation signal into the light source. The modulation signal is used to drive the light source to output an optical signal whose frequency changes linearly with time, such as an optical 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 optical 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).

[0229] It should be noted that Figures 20a and 20b above are illustrated using the calibration path (the path containing the first beam splitter 112, polarization transmission element 211, polarization adjustment element 212, optical delay line 310, first reflection element 411, second reflection element 412, mixer 114, photodetector 115, amplifier 118, analog-to-digital converter 119, and processing element 116) in the frequency modulation photoelectric circuit 110 as examples. However, the relevant content of these components also applies to the target measurement path 113 (the path containing the third beam splitter shown in Figure 6) in the frequency modulation photoelectric circuit 110. The path containing element 1131, polarization light transmission element 1132, mixer 1133, photodetector 1134, amplifier 1135, analog-to-digital converter 1136, and processing element 1137, or the path containing optical processing element 1138, polarization light transmission element 1132, mixer 1133, photodetector 1134, amplifier 1135, analog-to-digital converter 1136, and processing element 1137 as shown in FIG. 19, and the mixer 1133 in the target measurement path 113 and the mixer 114 in the calibration path can be of the same type or different types.

[0230] For example, combining Figures 6, 20a, and 20b, Figures 20c, 20b, and 20e show three possible implementations:

[0231] In the frequency modulation optoelectronic circuit 110 shown in Figure 20c, the first beam splitter 112 on the calibration path includes a first beam splitter 1121 and a second beam splitter 1122, the mixer 114 is a 180° optical mixer, the photodetector 115 includes PD1 and PD2, the amplifier 118 is a TIA 1180, the analog-to-digital converter 119 is an ADC 1190, and the processing element 116 is a DSP 1160. On the target measurement path 113, the third beam splitter 1131 is a third beam splitter 11310, the mixer 1133 is a 180° optical mixer, the photodetector 1134 includes PD3 and PD4, the amplifier 1135 is a TIA 11350, the analog-to-digital converter 1136 is an ADC 11360, and the processing element 1137 is a DSP 11370.

[0232] In the frequency modulation optoelectronic circuit 110 shown in Figure 20d, the first beam splitter 112 on the calibration path includes a first beam splitter 1121 and a second beam splitter 1122; the mixer 114 is a 90° optical mixer; the photodetector 115 includes PD11, PD12, PD21 and PD22; the amplifier 118 includes TIA 1181 and TIA 1182; the analog-to-digital converter 119 includes ADC 1191 and ADC 1192; and the processing element 116 is a DSP 1160. On the target measurement path 113, the third beam splitter 1131 is a third beam splitter 11310; the mixer 1133 is a 180° optical mixer; the photodetector 1134 includes PD3 and PD4; the amplifier 1135 is a TIA 11350; the analog-to-digital converter 1136 is an ADC 11360; and the processing element 1137 is a DSP 11370.

[0233] In the frequency modulation optoelectronic circuit 110 shown in Figure 20e, the first beam splitter 112 on the calibration path includes a first beam splitter 1121 and a second beam splitter 1122, the mixer 114 is a 180° optical mixer, the photodetector 115 includes PD1 and PD2, the amplifier 118 is a TIA 1180, the analog-to-digital converter 119 is an ADC 1190, and the processing element 116 is a DSP 1160. On the target measurement path 113, the third beam splitter 1131 is a third beam splitter 11310, the mixer 1133 is a 90° optical mixer, the photodetector 1134 includes PD31, PD32, PD41 and PD42, the amplifier 1135 includes TIA 11351 and TIA 11352, the analog-to-digital converter 1136 includes ADC 11361 and ADC 11362, and the processing element 1137 is a DSP 11370.

[0234] Of course, there are other implementations, which will not be listed here.

[0235] Furthermore, the components on the calibration path and target measurement path 113 in the frequency modulation optoelectronic circuit 110 described above are also applicable to the calibration path and target measurement path in other frequency modulation optoelectronic circuits, such as the calibration path and target measurement path 123 to target measurement path 1N3 in the frequency modulation optoelectronic circuits 120 to 1N0 in Figures 16, 17, 18a to 18c, and 19. In different frequency modulation optoelectronic 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 be of the same type or different types; this application does not limit this.

[0236] Furthermore, the above content only uses FMCW LiDAR as an example to introduce the internal structure of the signal processing device. However, it should be understood that the above signal processing device can also be applied to other application scenarios that require linear frequency modulation. For example, in some 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 various devices on its target measurement path are connected by 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 optical delay lines.

[0237] 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 FIG21. The detection device 2100 includes a signal processing device 2110, 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 FIG9b, FIG11, FIG12, and FIG14 to FIG18c.

[0238] Alternatively, the detection device 2100 can be a lidar, such as an FMCW LiDAR.

[0239] Optionally, as shown in Figure 21 above, the detection device 2100 may further include a window 2120, which is used to protect the internal signal processing device 2110 and can transmit the light signal emitted by the signal processing device 2110.

[0240] It should be noted that the detection device architecture shown in Figure 21 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.

[0241] 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 22. This terminal device 2200 may include the signal processing device described above, or it may include a detection device 2210. The detection device 2210 may be a detection device from any of the above embodiments, such as the detection device 2100 in Figure 21.

[0242] Optionally, as shown in Figure 22 above, the terminal device 2200 may further include a processor 2220, which is used to call programs or instructions to control the operation of the detection device 2210. Furthermore, the processor 2220 may also receive target-related information from the detection device 2210. When the terminal device 2200 is a vehicle, the processor 2220 may also perform vehicle path planning, braking, or starting based on the 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.

[0243] Furthermore, optionally, the terminal device 2200 may also include a memory 2230 for storing programs or instructions. Of course, the terminal device 2200 may also include other devices, such as wireless communication devices.

[0244] Processor 2220 may include one or more processing units. For example, processor 2220 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.

[0245] The memory 2230 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.

[0246] For example, the terminal device 2200 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.).

[0247] It should be noted that 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 make specific limitations in this regard.

[0248] In the above content, "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.

[0249] 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.

[0250] 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 internal logic. The terms "first," "second," "third," and similar expressions 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

1. A signal processing device, characterized by, include: Frequency modulation photoelectric circuit; The frequency modulation optoelectronic circuit includes a light source, a first beam splitter, a polarization processing element, an optical delay line, a first reflector, a second reflector, a mixer, a photodetector, a processing element, and a driving circuit. The polarization processing element has a first end, a second end, a third end, and a fourth end. The first end is connected to the first beam splitter, the second end is connected to the first end of the optical delay line, the third end is connected to the second reflector, the fourth end is connected to the mixer, and the second end of the optical delay line is connected to the first reflector.

2. The apparatus of claim 1, wherein, The polarization processing element includes a polarization light transmission element and a polarization light adjustment element, and both the polarization light transmission element and the polarization light adjustment element have a first end, a second end and a third end; The polarization transmission element is unidirectional, from the first end to the second end and from the second end to the third end. The first end of the polarization transmission element is connected to the first beam splitter, the second end of the polarization transmission element is connected to the first end of the polarization adjustment element, the third end of the polarization transmission element is connected to the mixer, the second end of the polarization adjustment element is connected to the first end of the optical delay line, and the third end of the polarization adjustment element is connected to the second reflection element.

3. The apparatus of claim 2, wherein, The polarization transmission element is a circulator.

4. The apparatus of claim 2 or 3, wherein, The polarization adjustment element includes a polarization beam splitter PBS and a quarter-wave plate. The PBS has a first end, a second end, and a third end. P-light or TE-light is transmitted between the first end and the second end of the PBS, and S-light or TM-light is reflected between the second end and the third end of the PBS. The first end of the PBS is connected to the polarization transmission element, the second end of the PBS is connected to the first end of the quarter-wave plate, the second end of the quarter-wave plate is connected to the first end of the optical delay line, and the third end of the PBS is connected to the second reflection element.

5. The apparatus of claim 2 or 3, wherein, The polarization adjustment element includes a polarization beam splitter PBS and a quarter-wave plate. The PBS has a first end, a second end, and a third end. P-light or TE-light is transmitted between the first end and the second end of the PBS, and S-light or TM-light is reflected between the second end and the third end of the PBS. The first end of the PBS is connected to the second reflective element, the second end of the PBS is connected to the first end of the quarter-wave plate, the second end of the quarter-wave plate is connected to the first end of the optical delay line, and the third end of the PBS is connected to the polarization light transmission element.

6. The apparatus of claim 2 or 3, wherein, The polarization adjustment element includes a polarization rotating beam splitter (PSR) and a quarter-wave plate. The PSR has a first end, a second end, and a third end. The first end and the second end of the PSR transmit optical signals in the original polarization direction, and the second end and the third end of the PSR transmit optical signals in the polarization direction after being rotated by 90°. The first end of the PSR is connected to the polarization transmission element, the second end of the PSR is connected to the first end of the quarter-wave plate, the second end of the quarter-wave plate is connected to the first end of the optical delay line, and the third end of the PSR is connected to the second reflection element.

7. The apparatus of claim 2 or 3, wherein The polarization adjustment element includes a polarization rotating beam splitter (PSR) and a quarter-wave plate. The PSR has a first end, a second end, and a third end. The first end and the second end of the PSR transmit optical signals in the original polarization direction, and the second end and the third end of the PSR transmit optical signals in the polarization direction after a 90° rotation. The first end of the PSR is connected to the second reflective element, the second end of the PSR is connected to the first end of the quarter-wave plate, the second end of the quarter-wave plate is connected to the first end of the optical delay line, and the third end of the PSR is connected to the polarization transmission element.

8. The apparatus of any one of claims 2 to 7, wherein, There are N frequency-modulated photoelectric circuits, where N is an integer greater than or equal to 2; The signal processing device further includes a beam combining element and a second beam splitting element. The N input terminals of the beam combining element are connected one-to-one with the N first beam splitting elements in the N frequency-modulated photoelectric circuits. The output terminal of the beam combining element is connected to the first terminal of the polarization light transmission element. The input terminal of the second beam splitting element is connected to the third terminal of the polarization light transmission element. The N output terminals of the second beam splitting element are connected one-to-one with the N mixers in the N frequency-modulated photoelectric circuits.

9. The apparatus of any one of claims 1 to 8, wherein, The first linearly polarized light, after being split by the first beam splitter, is converted into first circularly polarized light by the polarization processing element and output to the optical delay line. The first circularly polarized light, after passing through the optical delay line, enters the first reflector element and, after reflection by the first reflector element, becomes second circularly polarized light. The second circularly polarized light, after passing through the optical delay line, enters the polarization processing element and, after reflection by the polarization processing element, becomes second linearly polarized light and output to the second reflector element. The second linearly polarized light, after being reflected by the second reflector element, returns to the polarization processing element and, after reflection by the polarization processing element, becomes third circularly polarized light and output to the optical delay line. The third circularly polarized light, after passing through the optical delay line, enters the first reflector element and, after reflection by the first reflector element, becomes fourth circularly polarized light and enters the optical delay line. The fourth circularly polarized light, after passing through the optical delay line, enters the polarization processing element and, after reflection by the polarization processing element, becomes third linearly polarized light and output to the mixer.

10. The apparatus of claim 9, wherein, The first linearly polarized light has the same linear polarization state as the third linearly polarized light, the first linearly polarized light has the same or orthogonal linear polarization state as the second linearly polarized light, the first circularly polarized light has the same circular polarization state as the fourth circularly polarized light, and the second circularly polarized light has the same circular polarization state as the third circularly polarized light.

11. The apparatus of any one of claims 1 to 10, wherein, The optical delay line is either an optical fiber delay line or an on-chip integrated waveguide delay line.

12. The device of any one of claims 1 to 11, wherein, Either the first reflective element or the second reflective element is a fiber optic ring mirror, a Bragg grating, or a Sagnac ring.

13. The device of any one of claims 1 to 12, wherein, The frequency-modulated photoelectric circuit also includes a target measurement path. The first beam splitter has an input terminal, a first output terminal, a second output terminal, and a third output terminal. The mixer has a first input terminal, a second input terminal, and an output terminal. The input terminal of the first beam splitter is connected to the light source. The first output terminal of the first beam splitter is connected to the first terminal of the polarization processing element. The second output terminal of the first beam splitter is connected to the second input terminal of the mixer. The third output terminal of the first beam splitter is connected to the target measurement path. The first input terminal of the mixer is connected to the fourth terminal of the polarization processing element. The first beam splitter is used to split the light beam generated by the light source to obtain a local oscillator signal, a delay signal and a detection signal. It outputs the delay signal through its first output terminal, the local oscillator signal through its second output terminal and the detection signal through its 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.

14. The apparatus of claim 13, wherein, The first 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 first terminal of the polarization processing 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 light beam generated by the light source to obtain the detection signal and the intermediate light signal, 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 intermediate optical signal to obtain the local oscillator signal and the signal to be delayed. It outputs the signal to be delayed through its first output terminal and the local oscillator signal through its second output terminal.

15. The apparatus of claim 13 or 14, wherein, The signal processing device includes N frequency-modulated photoelectric circuits. The N frequency-modulated photoelectric circuits share the same target measurement path, or have their own target measurement paths, or partially share the same target measurement path and partially have their own target measurement paths, where N is an integer greater than or equal to 2.

16. The device of any one of claims 1 to 15, wherein, The frequency modulation optoelectronic circuit also includes an amplifier and an analog-to-digital converter, wherein the amplifier and the analog-to-digital converter are connected between the photodetector and the processing element; The amplifier is used to amplify the intermediate frequency signal from the photodetector element; The analog-to-digital converter is used to perform analog-to-digital conversion on the amplified intermediate frequency signal to obtain a digital signal.

17. A detection device, characterized in that Includes the signal processing apparatus as described in any one of claims 1 to 16.

18. A terminal device, comprising: Includes the detection device as described in claim 17.

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