Optical circulator and laser radar

Abstract

The invention provides an optical circulator and a laser radar. The optical circulator comprises two first birefringent crystals, a deflection sheet group and a second birefringent crystal, wherein the two first birefringent crystals are sequentially arranged in the direction of an optical path, and the optical axes of the second birefringent crystal and the first birefringent crystal are different in direction. When the optical circulator is used for emitting light, the first port and the second port are configured to enable laser signals to be incident along the optical axes of the two first birefringent crystals respectively. The third port is configured to enable laser in different polarization states to be output through the third port so as to be used as a laser radar light outlet port; when the optical circulator is used for receiving light, the third port is a signal inlet; and the deflection sheet group is configured to enable the received signal light to be emitted to the fourth port and the fifth port. As the third port is a light-out port and a light-in port, a bidirectional amplifier can be added behind the third port, so that the light-out signal and the light-in signal can be amplified by the same amplifier. Moreover, the first and second ports and the fourth and fifth ports are physically located at different positions, so that the isolation of received and transmitted signals can be realized.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and in particular to an optical circulator and a laser radar. Background Art

[0002] LiDAR is a device that measures the distance, speed and other parameters of a target object by sending lasers to the surface of the object and then measuring the arrival time of the reflected light beam.

[0003] In the field of laser technology, in order to reduce manufacturing costs and improve the signal-to-noise ratio, coaxial laser radars are often used, which share a common optical path for transmitting and receiving laser signals. At present, many coaxial laser radars use a semi-transmissive and semi-reflective lens design, that is, the laser transmission signal reaches the scanning component through the lens, and the receiving signal reaches the photodetector through the reflector, or the laser transmission signal reaches the scanning component through the reflector, and the receiving signal reaches the photodetector through the lens. However, since the same lens needs to take into account the reception and transmission of the coaxial laser radar, the output optical path must also simultaneously transmit two light beams in opposite directions, resulting in a low overall directionality of the laser radar, and it is difficult to avoid crosstalk between the receiving and transmitting lasers, which in turn causes system crosstalk. Therefore, the existing coaxial laser radar is not suitable for frequency modulated continuous wave laser signals (FMCW) whose transmission frequency is consistent with the echo frequency.

[0004] Laser radars that are suitable for frequency modulated continuous wave lasers usually use optical circulators to achieve the coaxial effect of optical components. However, since the existing circulators themselves have low directivity, the use of common optical circulators often also has low directivity, and may even cause false detection problems during laser radar detection.

[0005] It can be seen that proposing a laser radar that can avoid crosstalk between transmitted and received lasers and has high coaxiality has become a difficult problem that needs to be solved urgently in the field of laser technology. Summary of the invention

[0006] The present invention aims to at least solve the above-mentioned technical problem of how to achieve isolation of transmit and receive signals while improving the directionality of the laser radar and realizing bidirectional amplification, and proposes an optical circulator and a laser radar.

[0007] In order to achieve the purpose of the present invention, an optical circulator is provided, which is applied to laser radar; the optical circulator has a first port, a second port, a third port, a fourth port and a fifth port; the optical circulator comprises two first birefringent crystals, a deflection plate group and a second birefringent crystal arranged in sequence along the optical path direction; wherein,

[0008] The optical axes of the two first birefringent crystals are in different directions, and the optical axis of the second birefringent crystal is in the same direction as that of one of the first birefringent crystals;

[0009] When the optical circulator is used for emitting light in the laser radar, the first and second ports are used as light input ports; the first and second ports are configured to allow laser signals to be incident along the optical axes of the two first birefringent crystals respectively; the third port is arranged at the light output side of the second birefringent crystal, and the second birefringent crystal is configured to allow lasers of different polarization states to be output at the same position; the third port is used as a light output port;

[0010] When the optical circulator is used to receive light in the laser radar, the third port is used as a light input port; the deflection plate group is configured to make the received laser signal be emitted to the fourth and fifth ports respectively; the fourth and fifth ports are respectively arranged on the light output sides of the two first birefringent crystals and are different from the positions of the first and second ports; the fourth and fifth ports are used as light output ports.

[0011] Optionally, the thicknesses of the two first birefringent crystals and the second birefringent crystal in the optical path direction are equal.

[0012] Optionally, the deflection plate group includes a Faraday rotator mirror and a half-wave plate;

[0013] The Faraday rotator mirror is configured to deflect the laser signal by 45°; and the half-wave plate is configured to deflect the laser signal by 45°.

[0014] As another technical solution, the present invention also provides a laser radar, which includes a laser, a light splitting component, an optical circulator as described above, a bidirectional amplifier and a receiving component;

[0015] The light splitting component is coupled to the laser, the first port and the second port of the optical circulator respectively; the light splitting component is configured to split the laser signal emitted by the laser into two laser signals with different polarization directions, and respectively incident on the first port and the second port;

[0016] The bidirectional amplifier has a first transceiver end and a second transceiver end, the first transceiver end is coupled and connected to the third port of the optical circulator, and the second transceiver end is configured to emit a laser signal and receive a laser echo signal; the bidirectional amplifier is configured to amplify the laser emission signal and the laser echo signal;

[0017] The receiving component is coupled to the fourth port and the fifth port of the optical circulator respectively, and the receiving component is configured to receive laser signals in the fourth port and the fifth port respectively.

[0018] Optionally, a collimating lens is also included; one end of the collimating lens is coupled to the second transceiver end, and the other end is used to transmit laser signals to the external environment and receive laser echo signals reflected by the external environment.

[0019] Optionally, the bidirectional amplifier comprises a gain fiber and at least one pair of combiners and a pump source; wherein,

[0020] The gain optical fiber is used to transmit the laser signal and the laser echo signal;

[0021] At least one pair of the combiners is configured to couple the corresponding pump sources to the gain optical fiber; the pump sources are respectively arranged at the front end and / or the rear end of the gain optical fiber to enhance the laser signal and the laser echo signal.

[0022] Optionally, the gain fiber includes erbium-doped fiber or erbium-ytterbium co-doped fiber.

[0023] Optionally, the gain optical fiber adopts a front pump source, or a rear pump source, or a front and rear dual pump source.

[0024] Optionally, the receiving component includes two groups of photoelectric converters and receiving circuits respectively coupled to the fourth port and the fifth port; the receiving end of the photoelectric converter is coupled to the fourth port or the fifth port, and the transmitting end of the photoelectric converter is coupled to the receiving end of the receiving circuit;

[0025] The photoelectric converter is configured to convert the received laser signal into an electrical signal.

[0026] Optionally, the optical splitter assembly includes a first optical splitter, a second optical splitter and a modulator; a receiving end of the modulator is coupled to the laser, and the modulator is configured to modulate the frequency of the laser signal; a transmitting end of the modulator is respectively connected to the first optical splitter and the second optical splitter;

[0027] The first optical splitter and the second optical splitter are coupled to the first port and the second port respectively; the first optical splitter and the second optical splitter are configured to adjust the laser signal to different polarization states respectively.

[0028] Optionally, the optical splitter assembly further includes a third optical splitter and a fourth optical splitter; a receiving end of the third optical splitter and a receiving end of the fourth optical splitter are coupled to the first optical splitter and the second optical splitter respectively; the third optical splitter and the fourth optical splitter are configured to receive an intrinsic light portion of the laser signal;

[0029] The transmitting end of the third optical splitter and the transmitting end of the fourth optical splitter are respectively connected to the receiving component.

[0030] The present invention has the following beneficial effects:

[0031] The optical circulator provided by the present invention arranges two first birefringent crystals and a second birefringent crystal connected to one of the first birefringent crystals on both sides, so as to utilize the birefringence characteristics of the birefringent crystals to converge two laser signals incident from the first into one laser signal, and transmit and receive through a third port, thereby greatly improving the signal-to-noise ratio; and also utilizes the birefringence characteristics of the birefringent crystals to divide the incident laser signal into two laser signals, and the two laser signals can be emitted from the fourth port and the fifth port respectively, and because the positions of the first and second ports are different from those of the fourth and fifth ports, isolation of the transmitting and receiving signals can be achieved, thereby improving the directivity of the optical circulator.

[0032] The laser radar provided by the present invention first uses a splitter component to divide the laser signal emitted by the laser into two laser signals with different polarization directions, and the above-mentioned optical circulator converges the two laser signals into the same optical path and outputs them to the bidirectional amplifier to realize the common optical path for transmission and reception, thereby greatly improving the signal-to-noise ratio, and can realize that the transmitting and receiving signals share the same bidirectional amplifier, thereby saving equipment costs; then the optical circulator divides one laser signal into the same two optical paths and transmits them to the receiving component respectively, thereby avoiding crosstalk between the laser emission signal and the echo signal, and realizing isolation of the transmitting and receiving signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A simplified structural diagram of an optical circulator provided in Embodiment 1 of the present invention;

[0034] Figure 2 A schematic diagram of the structure of a laser radar provided in Example 2 of the present invention;

[0035] Figure 3 A simplified structural diagram of a bidirectional amplifier provided in Embodiment 2 of the present invention using front and rear dual pump sources;

[0036] Figure 4 This is a simplified structural diagram of a bidirectional amplifier provided in Embodiment 2 of the present invention when using a front pump source and a rear pump source. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the technical solution of the present invention, an optical circulator provided by the present invention and a laser radar using the same are described in detail below in conjunction with the accompanying drawings.

[0038] Example 1

[0039] Please refer to Figure 1, this embodiment provides an optical circulator, which has a first port a, a second port b, a third port c, a fourth port d and a fifth port e. The optical circulator includes two first birefringent crystals 1, a deflection plate group 3, and a second birefringent crystal 2 arranged in sequence along the optical path direction. Specifically, a birefringent crystal is an anisotropic crystal. When a beam of light is incident from the interface of a birefringent crystal, birefringence generally occurs and refracts into two beams of light, one of which is a beam of light refracted with a constant refractive index, namely ordinary light (hereinafter referred to as O light), and the other is a beam of light whose refractive index in the medium changes with the incident angle and polarization angle, namely extraordinary light (hereinafter referred to as E light); and birefringence does not occur when the light is incident along a special direction, and this special direction is the optical axis of the birefringent crystal.

[0040] In the optical circulator, the optical axis directions of the two first birefringent crystals 1 are different; the optical axis direction of the second birefringent crystal 2 is the same as the optical axis direction of one of the first birefringent crystals 1 .

[0041] Specifically, the first port a and the second port b are respectively arranged on the light incident side of the two first birefringent crystals 1, and the first port a and the second port b are configured to allow the laser signal to be incident along the optical axes of the two first birefringent crystals 1, respectively, so that the laser signal incident through the first port a and the second port b will not be birefringent after passing through the first birefringent crystal 1, but will remain emitted along the incident direction. The third port c is arranged on the light emitting side of the second birefringent crystal 2, and the third port c is configured to be able to emit the laser signal. The second birefringent crystal 2 is configured to allow laser signals of different polarization states to converge at the third port c. Moreover, as Figure 1 As shown, the deflection plate group 3 disposed between the two first birefringent crystals 1 and the second birefringent crystal 2 is configured to allow the laser signals incident from the first port a and the second port b to be emitted in the original polarization state.

[0042] In this way, when the optical circulator is used to output light in a laser radar, the first port a and the second port b can be used as light input ports, and the third port c can be used as a light output port, and the two laser signals incident from the first and second ports can be converged at the third port and output along the same optical path.

[0043] The fourth port d and the fifth port e are arranged on the first birefringent crystal 1, and are arranged on the same side of the first and second ports and are respectively arranged at positions different from the first port a and the second port b; the fourth port d and the fifth port e are configured to allow the laser signal to be emitted so as to be received by the external optoelectronic component. The third port c is also configured to allow the laser signal to be emitted; and the second birefringent crystal 2 can also use its own birefringence characteristics to divide the laser echo signal into two paths and emit them from different positions. The deflection plate group 3 is also configured to deflect the laser signal incident from the third port c at a specified angle, so that the two laser signals are deflected by birefringence in the two first birefringent crystals 1 respectively.

[0044] In this way, when the optical circulator is used to receive light in the laser radar, the third port c can be used as the light input port, the fourth port d and the fifth port e can be used as the light output ports, and one laser signal can be divided into two laser signals, which are emitted from the fourth and fifth ports respectively.

[0045] It can be seen that the third port c of the optical circulator in this embodiment can be used for both incident and outgoing laser signals, so as to realize that the laser signals are concentratedly emitted and incident from the same port, so that when the optical circulator is applied to the laser radar, coaxial transceiver can be realized, that is, the laser signal transmission and reception share the same optical path, thereby greatly improving the signal-to-noise ratio, and optical devices such as optical amplifiers and optical lenses can be reused to reduce the manufacturing cost of the equipment and reduce the size of the equipment. Moreover, the two laser signals emitted from the fourth port d and the fifth port e will not crosstalk with the two laser signals incident from the first port a and the second port b, so as to ensure that the laser signals sent and received by the optical circulator do not interfere with each other, and the isolation of the receiving and transmitting signals is realized, so as to improve the directionality of the optical circulator, so that it is suitable for transmitting continuous wave laser signals, such as frequency modulated continuous wave signals.

[0046] As Figure 1Taking the actual application of the light output and light input of the optical circulator shown as an example, specifically, in this light output state, two laser signals with different polarization states are injected into the first port a and the second port b. The laser signal will not be birefringent when it is incident on the first birefringent crystal 1, and the optical path will not be deflected and the polarization state will not change when passing through the deflection plate group 3. Since the optical axis of the second birefringent crystal 2 is arranged in the same direction as the optical axis of the first birefringent crystal 1 below, and is not arranged in the same direction as the optical axis of the first birefringent crystal 1 above, the laser signal incident from the first port a is not parallel to the optical axis of the second birefringent crystal 2 when it reaches the second birefringent crystal 2, and the corresponding refractive index is different, that is, the light is E light, and then the light path is deflected and deflected to the third port c, so as to converge together to the collimating lens at the third port c. In this way, the light of two different polarization states can be synthesized into the same light and emitted from the same port.

[0047] Under this incident light state, a laser signal containing two lasers in different polarization states is incident on the third port c. Since the refractive index of the E light changes with the polarization angle in the birefringent crystal, the two lasers in different polarization states will inevitably be divided into two light beams after being incident from the third port c, and will be emitted from different positions. Then, the two laser signals will be deflected by a specified angle after passing through the deflection component, and then respectively incident on the two first birefringent crystals 1. Since the polarization states of the two laser signals are different from the initial laser signals incident from the first port a and the second port b after deflection, the refractive index is also different from the refractive index of the initial laser signal, and the incident positions of the two are also different from the emission positions of the initial laser signal.

[0048] In some embodiments, the thicknesses of the two first birefringent crystals 1 and the second birefringent crystal 2 in the direction of the optical path are equal to ensure that the optical path of the laser signal in the first birefringent crystal 1 and the second birefringent crystal 2 is equal, so that the deflection angle of the laser signal is consistent, ensuring the consistency of the degree of optical path deflection, and further ensuring that the laser echo signal can return to the same horizontal axis after two deflections, so as to prevent crosstalk between laser signal optical paths in different directions.

[0049] In some preferred embodiments, Figure 1 As shown, the surfaces of the two first birefringent crystals 1 perpendicular to the optical path are flush, so that the two light input ports and the two light output ports of the optical circulator are on the same plane, thereby ensuring that there is no phase difference between the two incident lasers and the two output lasers.

[0050] like Figure 1As shown, in some embodiments, the deflection plate group 3 includes a Faraday rotator 31 and a half-wave plate 32. The Faraday rotator is a magneto-optical device with a deflection magnetic field inside, which can use the Faraday effect to rotate the polarization planes of the forward incident light and the reverse incident light of the same wavelength in the same direction by the same specified angle (θ). Therefore, Figure 1 As shown, the laser signal is deflected by an angle of θ when it first passes through the Faraday rotator, and continues to deflect by an angle of θ in the same direction when the laser signal is reflected and passes through the Faraday rotator again, that is, the laser echo signal is deflected by an angle of 2θ relative to the initial laser signal.

[0051] Specifically, the angle θ is 45°. The half-wave plate 32 is configured to deflect the laser signal passing therethrough by 45°.

[0052] In this way, Figure 1 As shown, when the laser signal is emitted from the first birefringent crystal 1 and then passes through the Faraday rotator, the polarization state of the laser signal will be deflected by 45°; and after the laser signal passes through the half-wave plate 32, the polarization state of the laser signal will be reversely deflected by 45°, so that the laser signal returns to the original polarization state. When the laser signal is emitted from the second birefringent crystal 2 and then passes through the half-wave plate 32, the polarization state of the laser signal will be deflected by 45°; and after the laser signal passes through the Faraday rotator, the polarization state of the laser signal will continue to deflect by 45°, so that the laser signal is deflected by 90° relative to the original polarization state, and the laser signal is E light for the first birefringent crystal 1.

[0053] It should be noted that the polarization state of the laser signal is not limited to Figure 1 If the Figure 1 When the polarization states of the two laser signals shown in the figure are both deflected by 90°, the optical circulator provided in this embodiment can still achieve the above technical effects.

[0054] As described above, the optical circulator provided in this embodiment is configured with two first birefringent crystals and a second birefringent crystal connected to one of the first birefringent crystals on both sides, so as to utilize the birefringence characteristics of the birefringent crystals themselves to converge the two laser signals incident from the first into one laser signal, and transmit and receive through a third port, thereby greatly improving the signal-to-noise ratio; and can also utilize the birefringence characteristics of the birefringent crystals themselves to divide the incident laser signal into two laser signals, and the two laser signals can be emitted from the fourth port and the fifth port respectively, so as to avoid interference between the transmitted and received laser signals, thereby improving the directivity of the optical circulator.

[0055] Example 2

[0056] The present embodiment provides a laser radar, comprising a laser, a spectrometer component sequentially arranged along an optical path, the optical circulator in Embodiment 1, a bidirectional amplifier, and a receiving component.

[0057] like Figure 2 As shown, the splitter component 04 is coupled to the laser 03 and the first port a and the second port b of the optical circulator 01 respectively; the splitter component 04 is configured to split the laser signal emitted by the laser 03 into two laser signals with different polarization directions, and respectively incident on the first port a and the second port b.

[0058] The bidirectional amplifier 02 has a first transceiver end and a second transceiver end, the first transceiver end is coupled to the third port c of the optical circulator 01, and the second transceiver end is configured to emit a laser signal and receive a laser echo signal, that is, a laser signal reflected and returned by the surface of the object to be measured. Specifically, in the bidirectional amplifier 02, the laser signal emission and reception share the same optical path, so that the signal-to-noise ratio of the laser radar can be greatly improved, and the bidirectional amplifier can be reused to reduce the manufacturing cost of the equipment and reduce the size of the equipment. Moreover, the bidirectional amplifier 02 is configured to amplify the laser emission signal and the laser echo signal, that is, to amplify the laser signal twice, so as to amplify the laser signal so that it is much higher than the low noise, thereby further improving the signal-to-noise ratio, and then improving the detection accuracy.

[0059] The receiving component is coupled to the fourth port d and the fifth port e of the optical circulator 01 respectively, and the receiving component is configured to receive the laser signals emitted from the fourth port d and the fifth port e respectively to analyze the laser echo signal, thereby realizing laser radar functions such as laser ranging.

[0060] Conventional bidirectional optical amplifiers usually require an isolator to be installed inside or transmit and receive through different paths to separate the transmitted and received laser signals. However, since the laser radar in this embodiment uses the optical circulator 01 as described in Example 1, the optical circulator 01 itself can separate the laser signal containing lasers in different polarization states into two laser signals. Therefore, the bidirectional amplifier in this embodiment does not need to be equipped with an isolator, and it only needs to achieve signal enhancement. In other words, the laser radar provided in this embodiment simplifies the bidirectional amplifier structure, thereby reducing the manufacturing cost.

[0061] In some embodiments, the laser radar further includes a collimating lens 06. Figure 1 As shown, one end of the collimating lens 06 is coupled to the second transceiver end of the bidirectional amplifier 02, and the other end is used to transmit laser signals to the external environment and receive laser echo signals reflected by the external environment.

[0062] like Figure 3As shown, in some embodiments, the bidirectional amplifier 02 includes a gain fiber 021 and at least one pair of beam combiners 022 and a pump source 023. The gain fiber 021 is used to transmit laser signals and laser echo signals; at least one pair of beam combiners 022 is configured to couple the corresponding pump source 023 with the gain fiber 021; the pump source 023 is respectively arranged at the front end and / or the rear end of the gain fiber to enhance the laser output signal and the laser echo signal. Specifically, the pump light can transmit the gain laser to the gain fiber 021, and the gain laser will be absorbed by the rare earth ions doped in the gain fiber 021, so as to be used for energy amplification of the output signal light when the laser signal and the laser echo signal are transmitted in the gain fiber 021.

[0063] Specifically, the output end of the beam combiner 022 is fused with the gain optical fiber 021 to form an optical path.

[0064] In some specific embodiments, Figure 4 As shown, the gain fiber 021 and the pump source 023 can be arranged in a front pump source or a rear pump source, that is, the pump source 023 is coupled to the front end or the rear end of the gain fiber 021; it should be noted that the "front end" and "rear end" of the gain fiber are set relative to the direction of the optical path. Specifically, the front end of the gain fiber is the light input end relative to the laser output signal, and the rear end of the gain fiber is the light input end relative to the laser echo signal. Or, as Figure 3 As shown, the gain fiber 021 and the pump source 023 may be arranged in a front-to-back dual pump source manner, that is, the two pump sources 023 are coupled to the two ends of the gain fiber 021 respectively.

[0065] It should be noted that the actual placement positions of the gain fiber 021 and the pump source 023 can be changed according to actual needs.

[0066] In some embodiments, the gain fiber 021 includes erbium-doped fiber (EDFA) or erbium-ytterbium co-doped fiber (EYDFA).

[0067] Moreover, the pump source 023 is, for example, a conventional high-power 940 nm pump source 023, which can provide a higher gain for the laser signal, thereby improving the detection efficiency as much as possible.

[0068] In some embodiments, the receiving component includes two groups of photoelectric converters 05 and receiving circuits respectively coupled to the fourth port d and the fifth port e. The receiving end of the photoelectric converter 05 is coupled to the fourth port d or the fifth port e, and the transmitting end of the photoelectric converter 05 is coupled to the receiving end of the receiving circuit; the photoelectric converter 05 is configured to convert the received laser signal into an electrical signal to facilitate analysis of the information contained in the laser signal.

[0069] In some embodiments, the optical splitter component 04 includes a first optical splitter 041, a second optical splitter 042 and a modulator 043. The receiving end of the modulator 043 is coupled to the laser 03, and the modulator 043 is configured to modulate the frequency of the laser signal; the transmitting end of the modulator 043 is respectively connected to the first optical splitter 041 and the second optical splitter 042. The first optical splitter 041 and the second optical splitter 042 are respectively coupled to the first port a and the second port b; the first optical splitter 041 and the second optical splitter 042 are respectively configured to adjust the laser signal to different polarization states, thereby transmitting laser signals of different polarization states to the first port a and the second port b, respectively. Specifically, as Figure 1 As shown, the polarization directions of the laser signals transmitted to the first port a and the second port b are orthogonal.

[0070] In some embodiments, Figure 2 As shown, the optical splitter component 04 further includes a third optical splitter 044 and a fourth optical splitter 045. The receiving end of the third optical splitter 044 and the receiving end of the fourth optical splitter 045 are coupled and connected to the first optical splitter 041 and the second optical splitter 042 respectively; the third optical splitter 044 and the fourth optical splitter 045 are configured to receive the intrinsic light part of the laser signal, and the transmitting end of the third optical splitter 044 and the transmitting end of the fourth optical splitter 045 are respectively connected to the receiving component to recover the laser signal that fails to enter the optical circulator 01, and can amplify the laser signal of the receiving component in the transmission direction.

[0071] As described above, the laser radar provided in this embodiment first uses a light splitting component to divide the laser signal emitted by the laser into two laser signals with different polarization directions, and uses an optical circulator to converge the two laser signals into the same optical path and output them to a bidirectional amplifier, so as to realize a common optical path for transmission and reception, thereby greatly improving the signal-to-noise ratio; and then uses an optical circulator to divide one laser signal into the same two optical paths and transmit them to the receiving component respectively, thereby avoiding mutual crosstalk between laser echo signals. Moreover, the laser radar can also realize that the transmitting and receiving signals share the same bidirectional amplifier, thereby saving equipment costs.

[0072] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. An optical circulator, applied to laser radar; characterized in that: It has a first port, a second port, a third port, a fourth port and a fifth port; the optical circulator includes two first birefringent crystals, a deflection plate group, and a second birefringent crystal arranged in sequence along the optical path direction; wherein, The optical axes of the two first birefringent crystals are in different directions, and the optical axis of the second birefringent crystal is in the same direction as that of one of the first birefringent crystals; When the optical circulator is used for emitting light in the laser radar, the first and second ports are used as light input ports; the first and second ports are configured to allow laser signals to be incident along the optical axes of the two first birefringent crystals respectively; the third port is arranged at the light output side of the second birefringent crystal, and the second birefringent crystal is configured to allow lasers of different polarization states to converge to the third port; the third port is used as a light output port; When the optical circulator is used to receive light in the laser radar, the third port is used as a light input port; the deflection plate group is configured to make the received laser signal be emitted to the fourth and fifth ports respectively; the fourth and fifth ports are respectively arranged on the light output sides of the two first birefringent crystals and are different from the positions of the first and second ports; the fourth and fifth ports are used as light output ports.

2. The optical circulator according to claim 1, characterized in that: The thicknesses of the two first birefringent crystals and the second birefringent crystal in the optical path direction are equal.

3. The optical circulator according to claim 1, characterized in that: The deflection plate group includes a Faraday rotator mirror and a half-wave plate; The Faraday rotator mirror is configured to deflect the laser signal by 45°; and the half-wave plate is configured to deflect the laser signal by 45°.

4. A laser radar, characterized in that: It comprises a laser, a light splitting component, an optical circulator as claimed in any one of claims 1 to 3, a bidirectional amplifier and a receiving component; The light splitting component is coupled to the laser, the first port and the second port of the optical circulator respectively; the light splitting component is configured to split the laser signal emitted by the laser into two laser signals with different polarization directions, and respectively incident on the first port and the second port; The bidirectional amplifier has a first transceiver end and a second transceiver end, the first transceiver end is coupled and connected to the third port of the optical circulator, and the second transceiver end is configured to emit a laser signal and receive a laser echo signal; the bidirectional amplifier is configured to amplify the laser emission signal and the laser echo signal; The receiving component is coupled to the fourth port and the fifth port of the optical circulator respectively, and the receiving component is configured to receive laser signals in the fourth port and the fifth port respectively.

5. The laser radar according to claim 4, characterized in that: It also includes a collimating lens; one end of the collimating lens is coupled to the second transceiver end, and the other end is used to transmit laser signals to the external environment and receive laser echo signals reflected by the external environment.

6. The laser radar according to claim 5, characterized in that: The bidirectional amplifier comprises a gain fiber and at least one pair of combiners and a pump source; wherein, The gain optical fiber is used to transmit the laser signal and the laser echo signal; At least one pair of the combiners is configured to couple the corresponding pump sources to the gain optical fiber; the pump sources are respectively arranged at the front end and / or the rear end of the gain optical fiber to enhance the laser output signal and the laser echo signal.

7. The laser radar according to claim 6, characterized in that: The gain optical fiber includes erbium-doped optical fiber or erbium-ytterbium co-doped optical fiber.

8. The laser radar according to claim 7, characterized in that: The gain optical fiber and the pump source are arranged in a front pump source, a rear pump source, or a front and rear dual pump source.

9. The laser radar according to claim 4, characterized in that: The receiving component comprises two groups of photoelectric converters and receiving circuits respectively coupled to the fourth port and the fifth port; the receiving end of the photoelectric converter is coupled to the fourth port or the fifth port, and the transmitting end of the photoelectric converter is coupled to the receiving end of the receiving circuit; The photoelectric converter is configured to convert the received laser signal into an electrical signal.

10. The laser radar according to claim 4, characterized in that: The optical splitter assembly includes a first optical splitter, a second optical splitter and a modulator; the receiving end of the modulator is coupled to the laser, and the modulator is configured to modulate the frequency of the laser signal; the transmitting end of the modulator is respectively connected to the first optical splitter and the second optical splitter; The first optical splitter and the second optical splitter are coupled to the first port and the second port respectively; the first optical splitter and the second optical splitter are configured to adjust the laser signal to different polarization states respectively.

11. The laser radar according to claim 10, characterized in that: The optical splitter assembly further includes a third optical splitter and a fourth optical splitter; a receiving end of the third optical splitter and a receiving end of the fourth optical splitter are coupled and connected to the first optical splitter and the second optical splitter respectively; The third optical splitter and the fourth optical splitter are configured to receive an intrinsic light portion of the laser signal; The transmitting end of the third optical splitter and the transmitting end of the fourth optical splitter are respectively connected to the receiving component.

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