CN221926628U - Laser radar system - Google Patents

Abstract

The application relates to a lidar system comprising: the device comprises a laser, a frequency modulation module, a band-pass filter, a beam splitter, a pulse modulator, a transceiver module and a detection module, wherein the laser is used for optically coupling the echo signal and the local oscillator and then converting the coupled echo signal and the local oscillator into electric signals. The system generates at least four optical signals with different frequencies by frequency modulation of the received continuous laser by using the frequency modulation module, and enables the band-pass filter and the transceiver module to be matched, specifically, the band-pass filter and the transceiver module sequentially carry out band-pass filtering on the at least four optical signals with different frequencies and cycle the signals, so that only one optical signal with different frequencies passes through the band-pass filter in the same time period, and the pulse signal light with different frequencies is respectively emitted to a target to be detected and received back wave signals when the pulse signal light subsequently passes through the transceiver module, and the optical signals in the system can be transmitted through the light guide, thereby realizing the integration of the light beam scanning device.

Description

Laser radar system

Technical Field

The application relates to the technical field of laser radars, in particular to a laser radar system.

Background

The laser radar has obvious advantages in the aspects of ranging accuracy, three-dimensional perception, adaptability and the like. The traditional laser radar generally uses a mechanical rotation mode to perform light beam scanning, so that most laser radar products still have the defects of large volume, high cost and the like. Miniaturization and integration are the development directions of laser radars, and if solid-state laser radars can be realized on a chip, the power consumption and cost of the laser radars can be greatly reduced, and the reliability can be improved. However, the integration of the beam scanning device is a great technical difficulty.

Therefore, there is an increasing demand for laser radar systems to achieve all-optical integration.

Disclosure of utility model

In view of the above, it is necessary to provide a lidar system capable of achieving all-optical integration.

In a first aspect, the present application provides a lidar system comprising:

a laser for outputting continuous laser light;

The frequency modulation module is used for receiving the continuous laser and carrying out frequency modulation on the continuous laser to generate at least four optical signals with different frequencies;

The band-pass filter is used for sequentially carrying out band-pass filtering on the at least four optical signals with different frequencies and periodically circulating, so that only one optical signal with one frequency passes through the band-pass filter in the same time period;

the beam splitter is used for receiving the optical signal output by the band-pass filter and separating the optical signal into signal light and local oscillation light;

the pulse modulator is used for pulse modulating the signal light to generate pulse signal light;

The receiving and transmitting module is used for respectively transmitting the pulse signal light with at least four different frequencies to a target to be detected and receiving a echo signal;

the detection module is used for detecting the position of the probe, for optically coupling the echo signal and the local oscillator and converting the same into an electrical signal.

In one embodiment, the frequency modulation module comprises:

The at least one intensity modulator is used for receiving the continuous laser and carrying out carrier suppression double-sideband modulation on the continuous laser to obtain at least one first frequency optical signal and at least one second frequency optical signal;

And the high nonlinear device is used for performing four-wave mixing processing on the at least one first frequency optical signal and the at least one second frequency optical signal so as to generate at least four optical signals with different frequencies.

In one embodiment, the intensity modulator is a Mach-Zehnder interferometric modulator.

In one embodiment, the highly nonlinear device comprises a highly nonlinear optical fiber, a highly nonlinear chip, a highly nonlinear photonic crystal.

In one embodiment, the frequencies of the at least four different frequency optical signals are spaced apart at equal intervals.

In one embodiment, the band-pass filter comprises a tunable band-pass filter of the micro-ring resonator type, the center wavelength of the tunable band-pass filter of the micro-ring resonator type is changed by tuning the electrode voltage on the micro-ring, the optical signals of different frequencies are sequentially passed through, and the voltage cycle is set so that only one frequency of the optical signals passes through the band-pass filter in the same time period.

In one embodiment, the transceiver module comprises:

The circulator is used for transmitting pulse signal light to the channel selection unit and receiving echo signals sent by the channel selection unit, and sending the echo signals to the detection module;

And the channel selection unit is used for respectively transmitting the pulse signal light with at least four different frequencies to the target to be detected, receiving an echo signal returned by the target to be detected and transmitting the echo signal to the circulator.

In one embodiment, the channel selection unit comprises a wavelength division multiplexer.

In one embodiment, the detection module comprises:

the coupler is used for coupling the echo signal and the local oscillation light;

And the detector is used for receiving the coupled optical signals, performing beat frequency and converting the optical signals into electric signals.

In one embodiment, the detector comprises a balanced detector.

According to the laser radar system, the frequency modulation module is used for carrying out frequency modulation on received continuous laser to generate at least four optical signals with different frequencies, the band-pass filter and the receiving and transmitting module are matched for use, and specifically, the band-pass filter is sequentially carried out on the at least four optical signals with different frequencies and the optical signals are circulated periodically, so that only one optical signal with different frequencies in the same time period passes through the band-pass filter, and pulse signal light with different frequencies is respectively emitted to a target to be detected and received back wave signals when the laser radar system subsequently passes through the receiving and transmitting module, and the optical signals in the system can be transmitted through the light guide, so that the integration of the light beam scanning device can be realized. When the system is applied to the wind measuring field, a three-dimensional wind field can be constructed. Compared with the automatic mode such as mechanical scanning or micromechanical control, the laser radar stability can be improved by adopting the static mode to simultaneously emit at least four light beams, and the volume and weight of the radar can be greatly reduced by adopting the integrated device.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the related art, the drawings that are required to be used in the embodiments or the related technical descriptions will be briefly described, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to the drawings without inventive effort for those skilled in the art.

FIG. 1 is a schematic diagram of a lidar system in one embodiment;

Fig. 2 is a schematic diagram of a lidar system in another embodiment.

Detailed Description

In order that the above objects, features and advantages of the application will be readily understood, a more particular description of the application will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. The present application may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the application, whereby the application is not limited to the specific embodiments disclosed below.

In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present application and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present application.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.

In the present application, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.

In the present application, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.

It will be understood that when an element is referred to as being "fixed" or "disposed" on another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like are used herein for illustrative purposes only and are not meant to be the only embodiment.

Laser radars typically employ a servo system or multiple beam scanning to achieve three-dimensional detection. Servo systems are difficult to accommodate for the radar miniaturization due to their high price and large volume. The multi-beam scanning method is a most preferred approach for miniaturized lidar.

In order to realize accurate three-dimensional field detection, four light beams are generally adopted for three-dimensional field construction. Conventional four-beam lidar often employs a1×4 light-splitting approach to separate four beams of light. The usual optical switches are magneto-optical switches, MEMS optical switches, etc. The optical switch has high cost and can not realize all-optical integration by virtue of the composition of a separating device.

Full optical integration of the lidar system is achieved because although the lidar system is powerful, its wide use is limited due to its size, weight and power requirements. To make lidar systems more economical, lighter, it is desirable to integrate the optical components more tightly and enable mass production. With the development of integrated photonic chip industry, lidars can become lighter, avoid moving parts, and be manufactured in larger batches, thereby reducing the cost of the lidar device.

As described above, conventional four-beam lidar often uses a1×4 light-splitting method to split four beams of light. The usual optical switches are magneto-optical switches, MEMS optical switches, etc. For example, the MEMS optical switch is a function of engraving a plurality of tiny mirrors on a silicon crystal, and rotating a micromirror array by electrostatic force or electromagnetic force, thereby changing the propagation direction of input light to realize on-off of an optical path. The method for switching the light beam by means of the micro-mechanical motion in space makes the optical switch high in cost, and the optical switch cannot realize all-optical integration by means of the composition of the separating devices.

In order to achieve full optical integration of the lidar, as shown in fig. 1, an embodiment of the present application provides a lidar system, which includes:

A laser 102 for outputting continuous laser light; the frequency modulation module 104 is configured to receive the continuous laser and perform frequency modulation on the continuous laser to generate at least four optical signals with different frequencies; a band-pass filter 106 for sequentially band-pass filtering the at least four optical signals of different frequencies and periodically cycling such that only one optical signal of one frequency passes through the band-pass filter in the same period of time; a beam splitter 106, configured to receive the optical signal output by the band-pass filter, and split the optical signal into signal light and local oscillation light; a pulse modulator 110 for pulse-modulating the signal light to generate pulse signal light; the transceiver module 112 is configured to transmit the at least four pulse signal lights with different frequencies to a target to be detected, and receive a echo signal; the detection module 114 is configured to optically couple the echo signal and the local oscillator and convert the echo signal and the local oscillator into an electrical signal.

Illustratively, the lidar system includes a laser 102, a frequency modulation module 102, a bandpass filter 106, a beam splitter 108, a pulse modulator 110, a transceiver module 112, a detection module 114; wherein the laser 102 outputs a continuous laser light at a frequency f 0. Alternatively, laser 102 outputs continuous laser light at frequencies f0+Δf and f0- Δf.

The continuous laser light is incident on the frequency modulation module 102, which receives the continuous laser light and frequency modulates the continuous laser light to generate at least four optical signals with different frequencies, for example, f0+Δf, f0- Δf, f0+3Δf, and f0-3Δf, which may be respectively transmitted to the band-pass filter 106. It will be appreciated that the bandpass filter is an optical bandpass filter for filtering optical signals of different frequencies. The band-pass filter 106 sequentially band-pass filters the at least four optical signals of different frequencies and periodically circulates such that only one optical signal of one frequency passes through the band-pass filter 106 and is transmitted to the beam splitter 108 in the same period of time; the beam splitter 108 splits the optical signal of each frequency incident into two paths, one path is local oscillation light, and the other path is signal light; the local oscillation light is directly transmitted to the detection module 114, and the signal light of the other path is continuously transmitted to the pulse modulator 110, and pulse modulation is performed by the pulse modulator 110 to obtain pulse signal light, it can be understood that the at least four different frequency optical signals are all modulated by the pulse modulator 110, so as to obtain at least four different frequency pulse signal lights, the at least four different frequency pulse signal lights are incident to the transceiver module 112, and at least four pulse signal lights with frequencies f0+Δf, f0- Δf, f0+3Δf and f0-3Δf are transmitted to the target to be detected by the transceiver module 112, and collide with the target to be detected to generate an echo signal with Doppler frequency shift; the detection module 114 receives the echo signal and the local oscillation light split by the beam splitter 108, and converts the echo signal and the local oscillation light into an electrical signal after coupling the echo signal and the local oscillation light.

In the laser radar system, the frequency modulation module is used for carrying out frequency modulation on the received continuous laser to generate at least four optical signals with different frequencies, the band-pass filter and the transceiver module are matched for use, and specifically, the band-pass filter is sequentially carried out on the at least four optical signals with different frequencies and the optical signals are circulated periodically, so that only one optical signal with different frequencies in the same time period passes through the band-pass filter, and when the optical signals subsequently pass through the transceiver module, the pulse signal light with different frequencies is respectively emitted to a target to be detected, and received wave signals are received, so that the optical signals in the system are all transmitted through the light guide, and the integration of the light beam scanning device can be realized. When the system is applied to the wind measuring field, a three-dimensional wind field can be constructed. Compared with the automatic mode such as mechanical scanning or micromechanical control, the laser radar stability can be improved by adopting the static mode to simultaneously emit at least four light beams, and the volume and weight of the radar can be greatly reduced by adopting the integrated device.

In an exemplary embodiment, as shown in fig. 2, a schematic diagram of a lidar system in another embodiment, where the frequency modulation module includes: at least one intensity modulator 1042 for receiving the continuous laser and performing carrier-suppressed double-sideband modulation on the continuous laser to obtain at least one first frequency optical signal and at least one second frequency optical signal; a high nonlinear device 1044 for performing four-wave mixing processing on the at least one first frequency optical signal and the at least one second frequency optical signal, thereby generating at least four different frequency optical signals.

Wherein four-wave mixing is a substantially nonlinear effect. The reason why the four-wave mixing occurs is that the refractive index of the optical fiber is changed by light of a certain wavelength, and the phase of the light wave is changed at a different frequency, thereby generating a light wave of a new wavelength. The highly nonlinear device can produce stronger refractive index modulation for light of different wavelengths, and thus the effect is more pronounced. It is understood that highly nonlinear devices include, but are not limited to, highly nonlinear optical fibers, highly nonlinear chips, highly nonlinear photonic crystals.

And each of the at least one intensity modulator 1042 performs carrier-suppressed double-sideband modulation on the continuous laser after receiving the continuous laser to obtain a first frequency optical signal and a second frequency optical signal.

Illustratively, the laser 102 outputs a continuous laser with a frequency f0, the continuous laser is incident on each intensity modulator 1042, and the intensity modulator 1042 performs carrier-suppressed double-sideband modulation on the continuous laser to obtain a first frequency optical signal f0+Δf and a second frequency optical signal f0- Δf; the first frequency optical signal is f0+delta f and the second frequency optical signals f 0-delta f are incident on a high-nonlinearity device, and the high-nonlinearity device carries out four-wave mixing processing on the first frequency optical signal f0+delta f and the second frequency optical signals f 0-delta f, so that four optical signals with different frequencies are generated.

For example, after four-wave mixing processing is performed on a first frequency optical signal with frequency f0+Δf and a second frequency optical signal with frequency f0- Δf, the high-nonlinearity device generates four different frequency optical signals, where the four different frequencies are f0+Δf, f0- Δf, f0+3Δf, and f0-3Δf, respectively, that is, the frequencies of the four different frequency optical signals are separated by an equal interval 2Δf.

In this embodiment, carrier suppression double-sideband modulation is adopted for incident laser to generate optical signals with two frequencies, so that the basic condition of realizing four-wave mixing can be satisfied, and multiple optical wavelengths generated by four-wave mixing are separated at equal intervals, so that the frequency difference of the multiple optical wavelengths is relatively accurate.

In one exemplary embodiment, the intensity modulator is a Mach-Zehnder interferometric modulator.

Illustratively, the Mach-Zehnder interferometric modulator modulates at a modulation frequency Δf, performs carrier-suppressed double sideband modulation by controlling the bias point, and modulates the continuous laser light incident on the Mach-Zehnder interferometric modulator at a frequency f0 into a first frequency optical signal at a frequency f0+Δf and a second frequency optical signal at a frequency f0- Δf.

In this embodiment, a mach-zehnder interferometric modulator is used as the intensity modulator, which may be integrated into an optical chip with other optoelectronic devices and circuits.

In an exemplary embodiment, the frequencies of the at least four different frequency optical signals are spaced apart at equal intervals.

By way of example, since the high nonlinear device performs four-wave mixing processing on a first frequency optical signal having a frequency of f0+Δf and a second frequency optical signal having a frequency of f0- Δf, four different frequency optical signals are generated, the four different frequencies being f0+Δf, f0- Δf, f0+3Δf, and f0-3Δf, respectively, i.e., the frequencies of the four different frequency optical signals are separated by an equal interval of 2Δf.

Further, when at least one first frequency optical signal and at least one second frequency optical signal are input into the high nonlinear device, the high nonlinear device performs four-wave mixing processing on the at least one first frequency optical signal and the at least one second frequency optical signal to generate at least four different frequency optical signals, and the frequencies of the at least four different frequency optical signals are separated at equal intervals. For example, the frequencies of the at least one first frequency optical signal are f0-5Δf and f0-3Δf, and the frequencies of the at least one second frequency optical signal are f0+3Δf and f0+5Δf, when the first frequency optical signal with the frequencies of f0-5Δf and f0-3Δf and the second frequency optical signal with the frequencies of f0+3Δf and f0+5Δf are input into the high nonlinear device, the high nonlinear device performs four-wave mixing processing on the at least one first frequency optical signal and the at least one second frequency optical signal to generate eight optical signals with different frequencies, wherein the eight different frequencies are f0-7Δf, f0-5Δf, f0-3Δf, f0- Δf, f0+Δf, f0+2Δf, f0+3Δf and f0+5Δf, that is, and the eight different frequencies of the optical signals are separated by an equal interval of 2 Δf.

That is, by increasing the number of optical signals input to the highly nonlinear device, more optical signal output can be achieved, and the system can be expanded to more beams.

In one embodiment, the number of the at least four different frequency optical signals is a multiple of four.

In this embodiment, the multiple light wavelengths are equally spaced apart, and the frequency difference between the multiple wavelengths is relatively precise.

In one exemplary embodiment, the bandpass filter 106 comprises a tunable bandpass filter of the microring resonator type, the center wavelength of which is changed by tuning the electrode voltage on the microring, sequentially passing optical signals of different frequencies, and setting the voltage cycle such that only one frequency of optical signal passes through the bandpass filter during the same time period.

Specifically, the band-pass filter 106 is an optical band-pass filter, and when at least four optical signals with different frequencies, such as f0+Δf, f0- Δf, f0+3Δf, and f0-3Δf, are transmitted to the optical band-pass filter, the optical band-pass filter sequentially passes the four optical signals.

In one exemplary embodiment, the transceiver module 112 includes: the circulator 1122 is configured to transmit the pulse signal light to the channel selection unit, receive the echo signal sent by the channel selection unit, and send the echo signal to the detection module; and the channel selection unit 1124 is configured to transmit the pulse signal lights with the at least four different frequencies to the target to be measured, receive an echo signal returned by the target to be measured, and send the echo signal to the circulator.

Among them, the channel selection, i.e., wavelength separation technology, can be realized by filters, wavelength division multiplexers, dispersion prisms, etc.

In this embodiment, through the cooperation of the circulator and the channel selection unit, the transmission of the pulse signal light with at least four different frequencies and the corresponding reception of the echo signal generating the doppler shift frequency can be realized.

Further, the channel selection unit 1124 includes a wavelength division multiplexer.

In this embodiment, when at least four optical signals with different frequencies, for example, the optical signals with the frequencies f0+Δf, f0- Δf, f0+3Δf, and f0-3Δf, are transmitted to the optical bandpass filter, the optical bandpass filter sequentially passes the optical signals with the frequencies f0+Δf, f0- Δf, f0+3Δf, and f0-3Δf, and the wavelength division multiplexer sequentially transmits the optical signals with the frequencies f0+Δf, f0- Δf, f0+3Δf, and f0-3Δf through channels with the central frequencies f0+Δf, f0- Δf, f0+3Δf, and f0-3Δf, respectively, so as to implement the emission of the laser radar with at least four beams.

In one exemplary embodiment, the detection module 114 includes: a coupler 1142 for coupling the echo signal and the local oscillator light; and a detector 1144, configured to receive the coupled signal, beat the signal, and convert the signal into an electrical signal.

Further, the detector 1144 is a balanced detector.

For example, when coherent detection can be performed, the coherent laser signal and the local oscillation signal are incident on the photosensitive surface of the detector together under the condition of meeting wavefront matching, so that beat frequency or coherent superposition is generated, and the magnitude of the output electric signal of the detector is in direct proportion to the square of the sum of the laser signal (echo signal) to be detected and the local oscillation signal. When the local oscillation light and the echo signal are received by the balance detector at the same time, the balance detector is in a coherent detection state, and the signal segment is processed by the balance detector, so that the output electric signal of the balance detector is proportional to the square of the sum of the echo signal and the local oscillation signal.

In the embodiment, a method of coherent detection is adopted for the target to be detected, and the coupled optical signals are subjected to beat frequency and then converted into the electric signals, so that a high-precision detection result of the target to be detected can be obtained; furthermore, by adopting the balance detector for detection, noise and interference signals can be counteracted, and only required signal components are reserved, so that the quality of signals is improved, and the signal-to-noise ratio of the signals is effectively improved.

Referring again to fig. 2, fig. 2 shows another embodiment of a lidar system comprising: a laser 102 for outputting continuous laser light; the Mach-Zehnder interferometric modulator is used for receiving the continuous laser and performing carrier suppression double-sideband modulation on the continuous laser to obtain at least one first frequency optical signal and at least one second frequency optical signal; a high nonlinear device 1044 for performing four-wave mixing processing on the at least one first frequency optical signal and the at least one second frequency optical signal, thereby generating at least four different frequency optical signals; the frequencies of the at least four different frequency optical signals are spaced apart at equal intervals; the tunable band-pass filter of the micro-ring resonator type, change the centre wavelength of the tunable band-pass filter of the micro-ring resonator type through tuning the electrode voltage on the micro-ring, let the optical signal of different frequency pass sequentially, and set up the periodic cycle of the voltage, make only optical signal of a frequency pass the band-pass filter in the identical time quantum; a beam splitter 108, configured to receive the optical signal output by the band-pass filter, and split the optical signal into signal light and local oscillation light; a pulse modulator 110 for pulse-modulating the signal light to generate pulse signal light; the circulator 1122 is configured to transmit the pulse signal light to the channel selection unit, receive the echo signal sent by the channel selection unit, and send the echo signal to the detection module; the wavelength division multiplexer 1124 is configured to transmit the pulse signal light with the at least four different frequencies to the target to be measured, receive an echo signal returned by the target to be measured, and send the echo signal to the circulator; a coupler 1142 for coupling the echo signal and the local oscillator light; and the balance detector is used for receiving the coupled optical signals, performing beat frequency and converting the optical signals into electric signals.

The traditional four-beam laser radar usually adopts magneto-optical switches, MEMS optical switches and other 1×4 optical switches to separate four beams of light. These devices are all discrete devices with complex internal structures, realized by crystalline and micromechanical structures. In an embodiment of the present application, four wavelengths are generated by using four-wave mixing; the wavelength division multiplexer is an all-optical integrated passive device, does not need external signal driving, and has higher reliability and stability. And a plurality of optical wavelengths generated by four-wave mixing are separated at equal intervals, and the frequency difference of the plurality of optical wavelengths is accurate. By increasing the number of optical signals input to the highly nonlinear device, more optical signal output can be achieved, and the system can be expanded to more beams.

In one embodiment, a lidar system comprises: a laser 102, an intensity modulator 1042, a high non-linear device 1044, an optical bandpass filter, a beam splitter 108, a pulse modulator 110, a circulator 1122, a wavelength division multiplexer 1124, a coupler 1142, a balanced detector; the laser 102 is used for outputting continuous laser light; the intensity modulator 1042 is used to generate a carrier suppressed double sideband signal and pulse modulate the signal; the high nonlinear device 1044 is configured to generate a four-wave mixing effect to generate a signal with four frequencies; the optical band-pass filter is used for switching four wavelengths; the beam splitter 108 is used for separating out signal light and local oscillation light; the pulse modulator 110 is configured to pulse-modulate the signal light to generate pulse signal light; circulator 1122 is used to transmit pulse signal light and receive echo signals; the wavelength division multiplexer 1124 is configured to transmit signals of four different wavelengths to a target to be measured, and receive backscattered signals; the coupler 1142 is configured to couple the signal light from the circulator 1122 and the local oscillation light from the beam splitter 108; the balance detector receives the two coupled signals, and performs beat frequency conversion to an electric signal.

Illustratively, the lidar system enables detection of a target to be detected by:

Emitting continuous laser with frequency f0 by a laser; the modulation frequency of the intensity modulator is set to Δf.

The continuous laser with frequency f0 is subjected to carrier-suppressed double-sideband modulation by an intensity modulator, and continuous lasers with frequencies f0+Δf and f0- Δf are generated.

The continuous laser with frequencies f0+delta f and f0-delta f is subjected to four-wave mixing effect by adopting a high nonlinear device, and continuous laser signals with frequencies f0+delta f, f0-delta f, f0+3 delta f and f0-3 delta f are generated.

The continuous laser signals with the four frequencies (f0+delta f, f0-delta f, f0+3 delta f and f0-3 delta f) are subjected to band-pass filtering through an optical band-pass filter, and the continuous laser signals with the frequencies of f0+delta f, f0-delta f, f0+3 delta f and f0-3 delta f are sequentially passed through and circulated periodically.

And the single signal light filtered by the optical band-pass filter is split by using a beam splitter, one path is the signal light which is transmitted to the pulse modulator, and the other path is the local oscillation light which is transmitted to the coupler.

The signal light output by the beam splitter is pulse-modulated by the pulse modulator to generate pulse signal light, and the pulse signal light is sent to the wavelength division multiplexer by the circulator.

The center frequencies of four channels of the wavelength division multiplexer are respectively set as f0+delta f, f0-delta f, f0+3delta f and f0-3delta f, and pulse signal light with four frequencies is sequentially transmitted and emitted to a target to be detected.

The pulse signal light collides with the target to be detected to generate Doppler frequency shift, and the backward scattered signal is received by the wavelength division multiplexer and is sent to the coupler through the circulator.

And the local oscillation light and the backward scattering light are coupled and then transmitted to the balance detector through the coupler, and Doppler frequency shift is measured so as to measure the speed of the target to be measured.

In this embodiment, the optical band-pass filter sequentially passes continuous laser signals with frequencies f0+Δf, f0- Δf, f0+3Δf, and f0-3Δf, and the wavelength division multiplexer sequentially transmits continuous laser signals with frequencies f0+Δf, f0- Δf, f0+3Δf, and f0-3Δf through channels with center frequencies of f0+Δf, f0- Δf, f0+3Δf, and f0-3Δf, respectively, so as to implement the emission of the four-beam laser radar. It will be appreciated that by increasing the number of optical signals input to the highly nonlinear device, more optical signal output can be achieved and the system can be expanded to more beams.

Specifically, in one embodiment, the laser radar system comprises a continuous laser with a center wavelength of 1550nm, a 25GHz Mach-Zehnder interferometric modulator, a highly nonlinear optical fiber, a 1550nm tunable bandpass filter, a beam splitter, a semiconductor optical amplifier, a circulator, a 1X 4-100GHz wavelength division multiplexer, a coupler and a balanced detector; the laser radar system realizes the detection of the target to be detected by the following modes:

emitting 1550nm continuous laser by a laser; the modulation frequency of the Mach-Zehnder interferometric modulator was set to 25GHz (0.2 nm).

And controlling the bias point to perform carrier suppression double-sideband modulation, and modulating 1550nm continuous laser into 1549.8nm continuous laser and 1550.2nm continuous laser.

Two continuous lasers with wavelengths of 1549.8nm and 1550.2nm are input to generate a four-wave mixing effect of high-order sidebands by adopting a high-nonlinearity optical fiber, and four continuous laser signals with wavelengths of 1549.4nm, 1549.8nm, 1550.2nm and 1550.6nm are generated.

The center wavelength of the band-pass filter of the tunable band-pass filter is adjusted, for example, the center wavelength of the filter is changed by tuning electrode voltage on a micro-ring through a micro-ring resonator type tunable band-pass filter shell, continuous laser signals with wavelengths of 1549.4nm, 1549.8nm, 1550.2nm and 1550.6nm are sequentially and singly passed, and the tunable band-pass filter can be set to realize periodic scanning by setting voltage periodic circulation, so that light with four wavelengths is sequentially circulated to emit light.

Splitting the single signal light filtered out by the tunable bandpass filter by using a beam splitter: one path is signal light emitted to the semiconductor optical amplifier; the other path is used as local oscillation light to be transmitted to the coupler for generating local oscillation signal light required by the pulse coherent laser radar.

The single signal light output by the beam splitter is subjected to optical switching by utilizing the optical switching function and the amplifying function of the semiconductor optical amplifier to realize pulse modulation and improve the power at the same time, so that pulse signal light required by the pulse coherent laser radar is generated and is sent to the C-band 100GHz wavelength division multiplexer through the circulator.

The center wavelengths of the four channels of the 1X 4-100GHz wavelength division multiplexer are respectively set to 1549.4nm, 1549.8nm, 1550.2nm and 1550.6nm, so that pulse signal light with different wavelengths is separated from the four channels: specifically, when the tunable bandpass filter gates the center wavelength of 1549.4nm, 1549.4nm light is output from the tunable bandpass filter, light of other wavelengths is filtered, light of 1549.4nm is emitted from a channel with the center wavelength of 1549.4nm after passing through the 1×4-100GHz wavelength division multiplexer, and other three channels have no light output, so that four-beam output is realized.

The pulse beam collides with the target to be detected to generate Doppler frequency shift, and the backward scattering signal is received by a 1X 4-100GHz wavelength division multiplexer and is sent to the coupler through the circulator.

And the local oscillation light and the backward scattering light are coupled and then transmitted to the balance detector through the coupler, and Doppler frequency shift is measured so as to measure the speed of the target to be measured.

The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The foregoing examples illustrate only a few embodiments of the application and are described in detail herein without thereby limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of the application should be assessed as that of the appended claims.

Claims (10)

1. A lidar system, comprising:

a laser for outputting continuous laser light;

the frequency modulation module is used for receiving the continuous laser and carrying out frequency modulation on the continuous laser to generate at least four optical signals with different frequencies;

A band-pass filter for sequentially carrying out band-pass filtering on the at least four optical signals with different frequencies and periodically circulating, so that only one optical signal with one frequency passes through the band-pass filter in the same time period;

The beam splitter is used for receiving the optical signal output by the band-pass filter and separating the optical signal into signal light and local oscillation light;

The pulse modulator is used for pulse modulating the signal light to generate pulse signal light;

The receiving and transmitting module is used for respectively transmitting the pulse signal light with at least four different frequencies to a target to be detected and receiving a echo signal;

and the detection module is used for converting the echo signal and the local oscillation optical coupling into an electric signal.

2. The lidar system of claim 1, wherein the frequency modulation module comprises:

The at least one intensity modulator is used for receiving the continuous laser and carrying out carrier suppression double-sideband modulation on the continuous laser to obtain at least one first frequency optical signal and at least one second frequency optical signal;

and the high nonlinear device is used for performing four-wave mixing processing on the at least one first frequency optical signal and the at least one second frequency optical signal so as to generate at least four optical signals with different frequencies.

3. The lidar system of claim 2, wherein the intensity modulator is a mach-zehnder interferometric modulator.

4. The lidar system of claim 2, wherein the highly nonlinear device comprises a highly nonlinear optical fiber, a highly nonlinear chip, a highly nonlinear photonic crystal.

5. The lidar system of claim 1, wherein the frequencies of the at least four different frequency optical signals are spaced apart at equal intervals.

6. The lidar system according to claim 1, wherein the band-pass filter comprises a tunable band-pass filter of a micro-ring resonator type, a center wavelength of which is changed by tuning an electrode voltage on a micro-ring, sequentially passing optical signals of different frequencies, and setting a voltage cycle such that only one frequency of the optical signals passes through the band-pass filter in the same period of time.

7. The lidar system of claim 1, wherein the transceiver module comprises:

The circulator is used for transmitting pulse signal light to the channel selection unit and receiving echo signals sent by the channel selection unit, and sending the echo signals to the detection module;

And the channel selection unit is used for respectively transmitting the pulse signal light with at least four different frequencies to a target to be detected, receiving an echo signal returned by the target to be detected and transmitting the echo signal to the circulator.

8. The lidar system of claim 7, wherein the channel selection unit comprises a wavelength division multiplexer.

9. The lidar system of claim 1, wherein the detection module comprises:

the coupler is used for coupling the echo signal and the local oscillation light;

And the detector is used for receiving the coupled optical signals, performing beat frequency and converting the optical signals into electric signals.

10. The lidar system of claim 9, wherein the detector comprises a balanced detector.