Single acousto-optic wind measurement laser radar system with high amplification efficiency

Abstract

The utility model discloses a single acousto-optic wind measurement laser radar system with high amplification efficiency. The single acousto-optic wind measurement laser radar system comprises a seed laser, an optical fiber beam splitter, a polarization beam splitter, an acousto-optic modulator, an acousto-optic driver, an optical fiber amplifier 1, a Faraday rotator mirror, an optical fiber amplifier 2, a circulator, a telescope, a coupler and a balance detector. Compared with the prior art, the combination of the polarization beam splitter and the Faraday rotating mirror is adopted, polarization states of light reflected by the Faraday rotating mirror for odd and even times are orthogonal, signal light with orthogonal polarization states is separated from stray light through a polarization separation principle, stray light in a system is inhibited, and the polarization of the system is improved. The peak power increase caused by interference of light of multiple frequencies in the main pulse is avoided, the system noise is also reduced, and the occurrence of abnormal frequency spectrums is avoided.

Description

Technical Field

[0001] The utility model relates to the field of radar detection, and particularly relates to a single acousto-optic wind-measuring lidar system with high amplification efficiency. Background Art

[0002] The wind-measuring lidar is based on the coherent detection method. By measuring the Doppler frequency shift of the aerosol backscattering signal, the wind speed information at different positions can be obtained. Most of the lasers in the wind-measuring lidar system are based on the master oscillator power amplification structure. The seed laser emits continuous laser, which is chopped and frequency-shifted by an acousto-optic modulator, and then passes through an optical fiber amplifier. The amplified pulse signal is transmitted into the air through a telescope. Both the single-pulse energy and the extinction ratio of the pulse signal are important indicators of the system. The single-pulse energy affects the maximum detection range of the radar; the higher the extinction ratio of the pulse signal, the weaker the leakage pulse interfering with the detection of the aerosol echo signal.

[0003] The commonly used wind-measuring lidar system adopts a one-way direct amplification scheme, and through two-stage optical fiber amplifiers, the single-pulse energy is amplified to the level required for the radar detection range; by cascading two acousto-optic modulators, the second acousto-optic modulator is used to synchronously turn off the leakage pulse to improve the extinction ratio of the pulse signal. The system block diagram is as Figure 1 shown. The seed laser emits single-frequency continuous laser, which is divided into local oscillator light and signal light by an optical fiber beam splitter. The signal light is modulated into pulse light by acousto-optic modulator 1, and then pre-amplified by optical fiber amplifier 1, and then passes through acousto-optic modulator 2 to turn off the leakage pulse, and then enters optical fiber amplifier 2, and then is transmitted through a circulator and a telescope. After the telescope receives the aerosol backscattering signal, it is transmitted to a 3 dB coupler through the circulator. The local oscillator light and the returned signal light are mixed by the 3 dB coupler and beat on the surface of the balanced detector, and the frequency-shifted information is obtained through signal processing.

[0004] This scheme mainly has two problems: one is that the optical fiber amplifier adopts a one-way direct amplification scheme. Due to the limited amplification ability of optical fiber amplifier 1, the output power requirement for the seed laser is high, increasing the radar cost; the other is that cascading two acousto-optic modulators has a high cost, and at the same time increases the volume and power consumption of the radar system. Therefore, in order to reduce the cost of the wind-measuring lidar system, reduce the radar volume and power consumption, a new radar scheme with high amplification efficiency and high extinction ratio is needed. Content of the Utility Model

[0005] The purpose of the utility model is to propose a single acousto-optic wind-measuring lidar system with high amplification efficiency in view of the existing one-way direct amplification scheme, which has limited amplifier amplification ability and high output power requirement for the seed laser, and in view of the cascading two acousto-optic modulator scheme, which has a high cost of using two acousto-optic modulators and at the same time increases the volume and power consumption of the radar system.

[0006] To achieve the above object, the present utility model adopts the following technical solutions:

[0007] A single acousto-optic wind-measuring lidar system with high amplification efficiency, comprising a seed laser, an optical fiber beam splitter, a polarization beam splitter, an acousto-optic modulator, an acousto-optic driver, an optical fiber amplifier 1, a Faraday rotator mirror, an optical fiber amplifier 2, a circulator, a telescope, a coupler and a balanced detector;

[0008] Among them, the seed laser emits single-frequency continuous laser, which is divided into local oscillator light and signal light by the optical fiber beam splitter; the signal light passes through the polarization beam splitter, then passes through the acousto-optic modulator, and after frequency shift and chopping, enters the optical fiber amplifier 1. The signal light amplified by the optical fiber amplifier 1 is reflected back into the optical fiber amplifier 1 by the Faraday rotator mirror, and is amplified again by the optical fiber amplifier 1 to achieve double-pass amplification; the signal light after secondary amplification enters the acousto-optic modulator, and the extinction ratio of the pulse signal is improved by using single acousto-optic double-pass; then the signal light is transmitted to the optical fiber amplifier 2 through the polarization beam splitter, and the energy of the signal light is amplified to the level required for the radar detection distance; then through the circulator, it is emitted into the air through the telescope, and after reflection in the air, a scattered return light signal is formed, which is received by the telescope, passes through the circulator, and enters the coupler;

[0009] The local oscillator light enters the coupler, is mixed with the scattered return light signal, reaches the surface of the balanced detector for beat frequency, and after signal processing, the Doppler frequency shift amount is extracted, and then the wind speed information is inversely calculated.

[0010] As a further preference of the present utility model, the polarization beam splitter includes a first port, a second port and a third port. The first port is connected to the optical fiber beam splitter, the third port is connected to the acousto-optic modulator, and the second port is connected to the optical fiber amplifier 2.

[0011] A single acousto-optic wind-measuring lidar system with high amplification efficiency proposed by the present utility model has the following beneficial effects compared with the prior art:

[0012] 1. The present utility model adopts the combination of a polarization beam splitter and a Faraday rotator mirror. The polarization states of the light reflected by the Faraday rotator mirror an odd number of times and an even number of times are orthogonal. Through the principle of polarization separation, the signal light with orthogonal polarization states is separated from the stray light, suppressing the stray light in the system, avoiding the increase in peak power caused by the interference of lights with multiple frequencies in the main pulse, reducing the system noise, and avoiding the appearance of abnormal spectra;

[0013] 2. The present utility model uses the Faraday rotator mirror to reflect the signal light of single-pass amplification back into the optical fiber amplifier 1 to achieve a double-pass amplification scheme, improving the amplification efficiency, reducing the power requirement for the seed laser, and thus reducing the cost of the seed laser;

[0014] 3. The present utility model simultaneously realizes a single acousto-optic double-pass scheme through the combination of a polarization beam splitter, an acousto-optic modulator, an optical fiber amplifier 1, and a Faraday rotator mirror. The signal light after double-pass amplification passes through the acousto-optic modulator again for secondary frequency shifting, and at the same time, the secondary pulse after the main pulse is turned off, so that the extinction ratio level of the double acousto-optic cascade scheme is achieved through the single acousto-optic double-pass scheme, reducing the cost of the radar system, shrinking the volume, and reducing the system power consumption;

[0015] 4. The present utility model realizes a single acousto-optic double-pass scheme and uses a single acousto-optic device to achieve a high extinction ratio. Description of the Drawings

[0016] Figure 1 is a schematic diagram of the optical system of a wind-measuring lidar for the existing single-pass direct amplification and cascaded acousto-optic scheme;

[0017] Figure 2 is a schematic diagram of the single acousto-optic wind-measuring lidar system with high amplification efficiency according to the present utility model;

[0018] Figure 3 is a schematic diagram of the optical path of the single acousto-optic wind-measuring lidar system with high amplification efficiency according to the present utility model. Detailed Embodiments

[0019] The following is a specific introduction to the present utility model in combination with the drawings and specific embodiments.

[0020] Embodiment 1: As Figure 2 shown, a single acousto-optic wind-measuring lidar system with high amplification efficiency includes a seed laser, an optical fiber beam splitter, a polarization beam splitter, an acousto-optic modulator, an acousto-optic driver, an optical fiber amplifier 1, a Faraday rotator mirror, an optical fiber amplifier 2, a circulator, a telescope, a coupler, and a balanced detector.

[0021] Among them, as Figure 3 shown, the seed laser emits single-frequency continuous laser, which is divided into local oscillator light and signal light by the optical fiber beam splitter. The signal light is transmitted from the first port of the polarization beam splitter to the third port, and then passes through the acousto-optic modulator. After frequency shifting and chopping, it enters the optical fiber amplifier 1. The optical fiber amplifier 1 is connected to the Faraday rotator mirror. The signal light after single-pass amplification by the optical fiber amplifier 1 is reflected back to the optical fiber amplifier 1 by the Faraday rotator mirror for secondary amplification to achieve double-pass amplification; the signal light after secondary amplification enters the acousto-optic modulator to improve the extinction ratio of the pulse signal by using a single acousto-optic double-pass.

[0022] The utility model uses a Faraday rotator mirror to reflect the singly amplified signal light back to the fiber amplifier 1, realizing double-pass amplification, improving the amplification efficiency, reducing the power requirement for the seed laser, and thus reducing the cost of the seed laser. At the same time, through the combination of a polarization beam splitter, an acousto-optic modulator, the fiber amplifier 1, and the Faraday rotator mirror, a single acousto-optic double-pass scheme is realized. The signal light after double-pass amplification passes through the acousto-optic modulator again for secondary frequency shift, and at the same time, the sub-pulse after the main pulse is turned off, so that the extinction ratio level of the double acousto-optic cascade scheme is achieved through the single acousto-optic double-pass scheme, reducing the cost of the radar system, shrinking the volume, and reducing the system power consumption.

[0023] In the utility model, a scheme of combining a polarization beam splitter and a Faraday rotator mirror is used. According to the principle of polarization separation, the light reflected an odd number of times and an even number of times by the Faraday rotator mirror is separated. The signal light is transmitted from the first port of the polarization beam splitter to the third port. After reaching the acousto-optic modulator, the signal light for secondary frequency shift in the system is reflected once by the Faraday rotator mirror, and the polarization state is changed by 90°. The stronger light in the stray light is reflected zero times and two times by the Faraday rotator mirror respectively, and the polarization states are changed by 0° and 180° respectively. Then the polarization states of the signal light and the stray light are orthogonal. After the signal light passes through the third port of the polarization beam splitter, it exits from the second port; after the stray light reaches the third port of the polarization beam splitter, it exits from the first port. Thus, the signal light and the stray light are separated. The second port of the polarization beam splitter is connected to the fiber amplifier 2, and the light entering the subsequent amplification module is mainly the signal light for secondary frequency shift, suppressing the stray light in the system.

[0024] Then the signal light passes through the third port of the polarization beam splitter and is transmitted to the second port, enters the fiber amplifier 2, amplifies the single-pulse energy to the level required for the radar detection range, is transmitted from the first port of the circulator to the second port, and is emitted into the air through the telescope.

[0025] After being reflected by the atmosphere, a scattered return light signal carrying Doppler frequency shift information is formed. After the scattered return light signal is received by the telescope, it is transmitted from the second port of the circulator to the third port and enters the coupler; the local oscillator light enters the coupler. After the scattered return light signal and the local oscillator light are mixed by the coupler, they reach the surface of the balanced detector for beating. After signal processing, the Doppler frequency shift amount is extracted, and then the wind speed information is inversely calculated.

[0026] The above shows and describes the basic principle, main features, and advantages of the utility model. Those skilled in the art of this industry should understand that the above embodiments do not limit the utility model in any form. Any technical solutions obtained by using equivalent replacement or equivalent transformation fall within the protection scope of the utility model.

Claims

1. A single acoustic and optical wind measurement laser radar system with high amplification efficiency, characterized in that: It includes a seed laser, a fiber beam splitter, a polarization beam splitter, an acousto-optic modulator, an acousto-optic driver, a fiber amplifier 1, a Faraday rotator, a fiber amplifier 2, a circulator, a telescope, a coupler and a balanced detector; The seed laser emits a single-frequency continuous laser, which is divided into a local oscillator light and a signal light through a fiber beam splitter; the signal light passes through a polarization beam splitter, and then passes through an acousto-optic modulator, and enters the fiber amplifier 1 after frequency shifting and chopping. The signal light amplified by the fiber amplifier 1 is reflected back to the fiber amplifier 1 through a Faraday rotator, and is amplified again by the fiber amplifier 1 to achieve double-pass amplification. The signal light after secondary amplification enters the acousto-optic modulator, and the extinction ratio of the pulse signal is improved by using a single acousto-optic double pass; then the signal light is transmitted to the fiber amplifier 2 through a polarization beam splitter, and the signal light energy is amplified to the level required for the radar detection distance; then it passes through a circulator, and is emitted into the air through a telescope, and forms a scattered light signal after reflection in the air, and after being received by the telescope, it passes through a circulator and enters a coupler; The local oscillator light enters the coupler, mixes with the scattered return light signal, and reaches the beat frequency on the surface of the balanced detector. After signal processing, the Doppler frequency shift is extracted, and then the wind speed information is inverted.

2. A high-amplification-efficiency single-acoustic-optical wind laser radar system according to claim 1, characterized in that: The polarization beam splitter comprises a first port, a second port and a third port, the first port is connected to the optical fiber beam splitter, the third port is connected to the acousto-optic modulator, and the second port is connected to the optical fiber amplifier 2 .

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