A dual polarization operating fiber laser module

Abstract

The utility model belongs to the technical field of laser, provide a kind of optical fiber laser module of dual polarization operation, including the seed source of sequential connection, beam splitter, acoustooptic modulator, optical fiber amplifier, dual polarization circulator, still include 2*2 coupler and 1 / 4 wave plate, the dual polarization circulator has three ports, and the branch output laser of beam splitter is input to the input end of one way in 2*2 coupler after 1 / 4 wave plate laser conversion, and dual polarization circulator output laser echo signal is input to the other input end of 2*2 coupler, and the output end of 2*2 coupler is used to connect to radar system. In the utility model, the laser echo signal of two polarization states is all realized beat frequency, can significantly enhance the signal intensity of detection point, improve the signal-to-noise ratio of detection signal, to increase the detectable distance and detection precision of laser radar.

Description

Technical Field

[0001] This invention belongs to the field of laser technology, and particularly relates to a fiber laser module that operates with dual polarization. Background Technology

[0002] LiDAR (Light Detection and Ranging) is an active modern optical remote sensing technology, a product of the combination of traditional radar technology and modern laser technology. The principle of LiDAR is to measure the distance, position, speed, and even shape of a target by emitting a laser beam and receiving its reflected signal. Essentially, it utilizes the propagation characteristics of light (constant speed of light) to achieve precise ranging, and then constructs a three-dimensional environment model using a large number of ranging points. LiDAR has advantages such as high angular resolution, high range resolution, high temporal resolution, high measurement accuracy, long detection range, multi-target detection, and strong anti-interference capabilities.

[0003] Lidar based on the coherent Doppler mechanism uses a narrow-linewidth polarization-maintaining fiber laser. The probe laser and the local oscillator light output by the laser have the same linear polarization state. The lidar emits the probe laser into the atmosphere. After being scattered by the atmosphere, the probe laser forms a backscattered laser echo signal, which is received by the lidar. The received laser echo signal is then mixed with the local oscillator light and fed into a balanced detector to extract the measurement information.

[0004] According to the detection principle, lidar can only respond to laser echo signals with the same polarization state as the local oscillator light. However, due to the depolarization effect of atmospheric scattering on the probe laser, the polarization state of some laser echo signals changes. Generally, the depolarization ratio in normal atmosphere is between 0.3 and 0.5, meaning that approximately 23% to 33% of the laser echo signals have a polarization state orthogonal to the local oscillator light. This portion of the echo signal is unresponsive to by lidar, and therefore, a single-polarization circulator is typically used to filter out this portion of the laser echo. This results in a waste of laser power and limits the detectable range of lidar. Therefore, it is necessary to provide a technical solution to solve this problem. Utility Model Content

[0005] In view of the above problems, the purpose of this utility model is to provide a fiber laser module that operates under dual polarization, in order to solve the technical problem that existing lidar has a limited detection range because it cannot make full use of the laser echo signal.

[0006] The present invention adopts the following technical solution:

[0007] The dual-polarization fiber laser module includes a seed source, a beam splitter, an acousto-optic modulator, a fiber amplifier, and a dual-polarization circulator connected in sequence, and also includes a 2*2 coupler and a 1 / 4 waveplate. The dual-polarization circulator has three ports.

[0008] Port 1 is connected to the fiber optic amplifier, port 2 serves as the detection laser output and laser echo signal receiver, port 3 is the laser echo signal output, one branch of the beam splitter's output laser is converted by a 1 / 4 waveplate laser and then input to one of the inputs of the 2*2 coupler, port 3 of the dual polarization circulator is connected to the other input of the 2*2 coupler, and the output of the 2*2 coupler is used to connect to the radar system.

[0009] Furthermore, the seed source is used to output a narrow-linewidth linearly polarized continuous laser, and the beam splitter is used to split the linearly polarized continuous laser into two beams, one of which is output to an acousto-optic modulator and the other is output to a quarter-wave plate.

[0010] Furthermore, the acousto-optic modulator is used to chop the input linearly polarized continuous laser to form a low-power pulsed laser, while simultaneously applying a frequency shift; the fiber amplifier is used to amplify the low-power pulsed laser into a high-power pulsed laser, and input it to port one of the dual polarization circulator.

[0011] Furthermore, the 1 / 4 wave plate is used to convert the polarization state of another linearly polarized continuous laser beam from linear polarization to circular polarization laser beam, and the circularly polarized laser beam is used as the local oscillator light input to one input terminal of the 2*2 coupler.

[0012] Furthermore, the 2*2 coupler is used to mix the local oscillator light and the laser echo signal to generate coherent beat frequency.

[0013] The beneficial effects of this invention are as follows: In this invention, the local oscillator light and the laser echo signal are mixed in a 2*2 coupler. The local oscillator light can be decomposed into two orthogonal linearly polarized light components. The laser echo signal also contains two orthogonal linearly polarized light states, both of which can coherently beat with the local oscillator light. Therefore, the signal strength at the detection point can be significantly enhanced, the signal-to-noise ratio of the detection signal can be improved, and the detectable distance and detection accuracy of the lidar can be increased. Attached Figure Description

[0014] Figure 1 This utility model provides a schematic diagram of a fiber laser module that operates with dual polarization. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this utility model patent clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the scope of the present utility model.

[0016] To illustrate the technical solution described in this utility model, specific embodiments are described below.

[0017] For ease of explanation, only the parts relevant to the embodiments of this utility model are shown.

[0018] Combination Figure 1 As shown, the dual-polarization fiber laser module provided in this embodiment includes a seed source 1, a beam splitter 2, an acousto-optic modulator 3, a fiber amplifier 4, and a dual-polarization circulator 5 connected in sequence. It also includes a 2*2 coupler 6 and a 1 / 4 waveplate 7. The dual-polarization circulator 5 has three ports.

[0019] In the diagram, the three ports are labeled as port 1, port 2, and port 3. Port 1 is connected to the fiber amplifier 4, port 2 serves as the output of the detection laser and the receiver of the laser echo signal, and port 3 is the output of the laser echo signal. One output laser from the beam splitter 2 is converted by the 1 / 4 waveplate 6 and then input to one input of the 2*2 coupler 7. Port 3 of the dual polarization circulator 5 is connected to the other input of the 2*2 coupler 7, and the output of the 2*2 coupler 7 is used to connect to the radar system 8.

[0020] Based on the above fiber laser module, the working principle of the fiber laser module is as follows:

[0021] First, the seed source outputs a narrow-linewidth linearly polarized continuous laser. The linearly polarized continuous laser is split into two laser beams by a beam splitter. One laser beam is output to an acousto-optic modulator, and the other laser beam is output to a quarter-wave plate.

[0022] An acousto-optic modulator chops the input linearly polarized continuous laser light to form a low-power pulsed laser light, while simultaneously applying a frequency shift. The low-power pulsed laser light is amplified by a fiber amplifier to become a high-power pulsed laser light, which is then input to port one of a dual-polarization circulator. The high-power pulsed laser light enters the dual-polarization circulator from port one and is output from port two into the external environment as a probe laser for lidar detection. The external atmosphere scatters the probe laser light, forming a backward laser echo signal. Port two of the dual-polarization circulator simultaneously receives the laser echo signal and outputs it to a 2x2 coupler through port three. Because the dual-polarization circulator operates with dual polarization, the laser echo signal output from port three contains two orthogonal linearly polarized light states simultaneously. Therefore, the laser echo signal retains the light signal whose polarization state has changed due to atmospheric depolarization.

[0023] Simultaneously, a quarter-wave plate converts the polarization state of the split-beam input linearly polarized continuous laser from linear to circular polarization, and the circularly polarized laser is input as the local oscillator to one input terminal of the 2*2 coupler. Additionally, the laser echo signal output from port three of the dual-polarization circulator is input to the other input terminal of the 2*2 coupler.

[0024] In the 2*2 coupler, the local oscillator light and the laser echo signal are mixed to generate a coherent beat frequency signal. This beat frequency signal is output from both output terminals of the 2*2 coupler and input to the radar system. The radar system extracts the detection information. The calculation process of the radar system is not the focus of this invention and will not be elaborated here. Since the local oscillator light is circularly polarized, it can be decomposed into two orthogonal linearly polarized components. The laser echo signal also contains two orthogonal linearly polarized light states. Therefore, both linearly polarized components and the two orthogonal linearly polarized light states can coherently beat. Furthermore, the measurement information carried by the two polarization states in the laser echo signal at the same time and location is the same. Therefore, both polarization states of the laser echo signal achieve beat frequency, which can significantly enhance the signal strength at the detection point, improve the signal-to-noise ratio of the detection signal, and thus increase the detectable range and detection accuracy of the lidar.

[0025] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A fiber laser module operating with dual polarization, characterized in that: The fiber laser module includes a seed source, a beam splitter, an acousto-optic modulator, a fiber amplifier, and a dual polarization circulator connected in sequence, and also includes a 2*2 coupler and a 1 / 4 waveplate. The dual polarization circulator has three ports. Port 1 is connected to the fiber optic amplifier, port 2 serves as the detection laser output and laser echo signal receiver, port 3 is the laser echo signal output, one branch of the beam splitter's output laser is converted by a 1 / 4 waveplate laser and then input to one of the inputs of the 2*2 coupler, port 3 of the dual polarization circulator is connected to the other input of the 2*2 coupler, and the output of the 2*2 coupler is used to connect to the radar system.

2. The fiber laser module operating under dual polarization as described in claim 1, characterized in that: The seed source is used to output a narrow-linewidth linearly polarized continuous laser, and the beam splitter is used to split the linearly polarized continuous laser into two beams, one of which is output to an acousto-optic modulator and the other is output to a quarter-wave plate.

3. The fiber laser module operating under dual polarization as described in claim 2, characterized in that: The acousto-optic modulator is used to chop the input linearly polarized continuous laser to form a low-power pulsed laser, while adding a frequency shift; the fiber amplifier is used to amplify the low-power pulsed laser into a high-power pulsed laser, and input it to port 1 of the dual polarization circulator.

4. The fiber laser module operating under dual polarization as described in claim 3, characterized in that: The quarter-wave plate is used to convert the polarization state of another linearly polarized continuous laser beam from linear polarization to circular polarization, and the circularly polarized laser beam is used as the local oscillator light input to one of the input terminals of the 2*2 coupler.

5. The fiber laser module operating under dual polarization as described in claim 4, characterized in that: The 2*2 coupler is used to mix the local oscillator light and the laser echo signal to generate coherent beat frequency.

Images