Photoelectric integrated double-frequency laser for coherent wind measurement

Abstract

The invention relates to a photoelectric integrated double-frequency laser for coherent wind measurement, which comprises a first light source module, a second light source module, a first coupler module, a second coupler module, a third coupler module, a first beam splitter module, a second beam splitter module, a third beam splitter module and a first balanced photoelectric detector module, a second balance photoelectric detector module, a modulator module, an optical phase-locked loop module and a transceiver. Based on the silicon-based optoelectronic chip technology and the photoelectric hybrid packaging technology on the structural level, the coupler, the beam splitter and the photoelectric detector are integrated on the silicon optical chip, and the silicon optical chip, the DFB chip, the coupling optical path, the electrical module and the like are packaged together by utilizing the photoelectric hybrid packaging technology, so that high-density integration is realized; a heterodyne digital optical phase-locked loop technology is applied to a system level, so that a specific frequency difference exists between output signal light and reference light, and pulse light with a high extinction ratio is generated in a modulator cascading mode. Compared with a conventional single-light-source system scheme, the heterodyne Doppler wind measurement laser radar system can greatly improve the integration level, reduce the power consumption and the cost, and is beneficial to mass production, and compared with a homodyne detection mode, heterodyne detection is higher in measurement speed, simpler in scheme and better in stability. The system has extremely high expansibility, and can be applied to systems of optical fiber sensing, laser remote sensing and cold atomic clocks through operations of replacing a transmitting-receiving device, modifying a control program and the like.

Description

Technical Field

[0001] The invention belongs to the field of coherent wind measurement laser radar, in particular to an optoelectronic integrated dual-frequency laser for coherent wind measurement. Background Art

[0002] Coherent wind lidar technology uses the Doppler effect to measure wind speed. The reflected laser beam is mixed with a strong reference light emitted from a light source and then interfered on a light detector. When suspended matter in the air (such as aerosols and particles) is blown by the wind, laser scattering occurs, causing the frequency of the reflected laser to change, which is called Doppler shift. The size of this frequency shift is related to the wind speed. Wind speed information can be obtained by analyzing the optical mixing signal output by the light detector. This method has been widely used in the fields of three-dimensional wind field measurement, atmospheric turbulence detection and tracking, aircraft wake vortex detection, etc., and is an important technical means to achieve airborne wind shear warning.

[0003] Existing technologies are all made with discrete devices. Although the existing all-fiber Doppler wind laser radar system has a high degree of integration, it is also large in size. The acousto-optic modulator used for chopping and frequency shifting has a large power consumption, and the balanced detector used has a large cost problem, which to a certain extent limits the further application of wind laser radar products. In the face of the larger-scale application needs of more types and smaller aircraft in the future, the application of traditional all-fiber Doppler wind laser radar systems faces considerable challenges. Summary of the invention

[0004] To solve the above problems of the prior art, the present invention aims to provide an optoelectronic integrated dual-frequency laser for coherent wind measurement; an optoelectronic integrated dual-frequency laser for coherent wind measurement is realized by using silicon-based optoelectronic technology and compact optoelectronic hybrid packaging technology.

[0005] The technical solution of the present application provides an optoelectronic integrated dual-frequency laser for coherent wind measurement, the device comprising a first light source module, a second light source module, a first coupler module, a second coupler module, a third coupler module, a first beam splitter module, a second beam splitter module, a first balanced photodetector module, a second balanced photodetector module, a modulator module, an optical phase-locked loop module, and a transceiver.

[0006] The optical phase-locked loop module is connected to the first light source module and the second light source module respectively to control the light output by the light source module and the light output by the light source module to be stable at a required frequency difference;

[0007] The signal light output by the first light source module is coupled through the first coupler module, the first coupler module is connected to the input end of the first beam splitter module, the first output end of the first beam splitter module is connected to the first balanced detector, the second output end is coupled to the modulator module, and the modulator module is coupled to the transceiver device;

[0008] The reference light output by the second light source module is coupled with the second coupler module, the second coupler module is connected to the input end of the second beam splitter module, the first output end of the second beam splitter module is connected to the first balanced detector, the balanced detector is used to feed back the beat signal of the signal light and the reference light to the optical phase-locked loop module to control the frequency difference of the light source, the second output end is connected to the input end of the third beam splitter module, the first output end of the third beam splitter module is connected to the second balanced detector module, the second output end is connected to the third coupler module, and is used to output reference light to meet other devices such as laser ranging that require dual light source output feedback, the second balanced detector module is coupled to the transceiver to obtain the echo signal and beat with the reference signal to obtain the frequency difference.

[0009] In the embodiment, the first light source module is composed of a DFB laser chip, a first lens, an isolator, a polarizer, and a second lens; the light emitted by the laser chip is collimated by the first lens and then incident on the isolator, and then reaches the polarizer after passing through the isolator. The light beam after passing through the polarizer becomes linearly polarized light, and then is focused by the second lens and then input into the first coupler module. The second light source module has the same structure as the first light source module.

[0010] The optical phase-locked loop includes a circuit control chip, a frequency detector chip, and an active loop filter; the circuit control chip realizes stable output of laser control by connecting two laser chips, and connects the reference frequency required for its output to the second input end of the frequency detector chip through an algorithm, connects the beat frequency signal obtained by the first balanced photodetector module to the first input end of the frequency detector chip to realize frequency judgment and output phase difference signal, and filters out the high-frequency signal through the loop filter and then connects it to the circuit control chip, and controls the laser frequency output by the DFB laser chip of the second light source module with current through a specific PID control algorithm, so as to realize that the frequency difference between the two light sources is stable at 200MHz.

[0011] In this embodiment, the Doppler frequency shift generated by the interaction between the emitted laser and the aerosol particles is used to obtain the movement speed of the aerosol particles in the visual direction. The wavelength of the emitted laser of the light source module is λ, the frequency is f0, the speed of light is c, the Doppler frequency shift caused by the movement of the aerosol particles is Δf, and the visual wind speed v LOS It can be expressed as:

[0012]

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1) The present invention is based on silicon-based optoelectronic technology and optoelectronic packaging technology. The required components are integrated on a silicon photonic chip and optoelectronically co-packaged with some other electrical chips, optical components, etc., which can effectively reduce the overall power consumption of the system and is conducive to the compact and miniaturized design of the system using the dual-light source laser, especially the coherent wind measurement lidar.

[0015] 2) The present invention uses dual light sources based on heterodyne optical phase-locked loop technology to achieve difference frequency, and uses on-chip modulator cascade modulation to perform chopping to achieve optical pulses with high extinction ratio. Compared with traditional coherent wind measurement lidar that uses AOM to achieve frequency shifting and chopping, the present invention can effectively reduce the cost and power consumption of the system while maintaining performance.

[0016] 3) The present invention has very strong scalability and can be applied not only to coherent wind measurement lidar systems, but also to the provision of an unused reference light coupling output interface, which can meet the needs of coherent ranging, fiber optic sensing, laser remote sensing, atomic clocks and other fields that require dual light source transmission and reception. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 It is an overall structural diagram of an optoelectronic integrated dual-frequency laser for coherent wind measurement provided in an embodiment of the present application.

[0019] Figure 2 This is a structural diagram of a light source module of an optoelectronic integrated dual-frequency laser for coherent wind measurement provided in an embodiment of the present application.

[0020] Figure 3 This is a structural diagram of a transceiver device of an optoelectronic integrated dual-frequency laser for coherent wind measurement provided in an embodiment of the present application.

[0021] Figure 4 This is a structural diagram of an optical phase-locked loop module of an optoelectronic integrated dual-frequency laser for coherent wind measurement provided in an embodiment of the present application. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with embodiments and drawings, but the protection scope of the present invention shall not be limited thereto.

[0023] Figure 1 The present invention is a structural diagram of an optoelectronic integrated dual-frequency laser for coherent wind measurement, which comprises an optical phase-locked loop module (13), a first light source module (1), a second light source module (2), a transceiver (12), and a first coupler module (3), a second coupler module (4), a third coupler module (11), a first beam splitter module (5), a second beam splitter module (6), a third beam splitter module (10), a modulator module (7), a first balanced photodetector module (8), and a second balanced photodetector module (9) on a chip;

[0024] The invention is characterized in that the optical phase-locked loop module (13) is connected to the first light source module (1) and the second light source module (2) respectively, so as to control the light output by the light source module (2) and the light output by the light source module (1) to be stable at a required frequency difference;

[0025] The signal light output by the first light source module (1) is directly coupled into the optical chip through the first coupler module (3) of the optical chip, the first coupler module (3) is connected to the input end of the first beam splitter module (5), the first output end of the first beam splitter module (5) is connected to the first balanced detector (8), the second output end is directly coupled to the modulator module (7), the modulator module (7) is coupled to the transceiver device (12) through optical fiber, and high-quality optical pulses are output;

[0026] The reference light output by the second light source module (2) is directly coupled through the second coupler module (4) of the optical chip. The second coupler module (4) is connected to the input end of the second beam splitter module (6). The first output end of the second beam splitter module (6) is connected to the first balanced detector (8). The balanced detector is used to feed back the beat signal of the signal light and the reference light to the optical phase-locked loop module to control the frequency difference of the light source. The second output end is connected to the input end of the third beam splitter module (10). The first output end of the third beam splitter module (10) is connected to the second balanced detector module (9). The second output end is connected to the third coupler module (11) to output the reference light to meet the needs of other fields, such as laser ranging devices that require dual light source output feedback. The second balanced detector module (9) is coupled to the transceiver (12) through optical fiber to obtain the echo signal and beat the reference signal to obtain the frequency difference.

[0027] Figure 2The present invention is a structural diagram of a light source module of an optoelectronic integrated dual-frequency laser for coherent wind measurement, which comprises a DFB laser chip (1-1), a first lens (1-2), an isolator (1-3), a polarizer (1-4), and a second lens (1-5). The invention is characterized in that the light emitted by the laser chip (1-1) is collimated by the first lens (1-2) and then incident on the isolator (1-3), and then reaches the polarizer (1-4) after passing through the isolator (1-3). The light beam after passing through the polarizer (1-4) becomes linearly polarized light, and then is focused by the second lens (1-5) and then input into the first coupler module (3). The structure of the second light source module (2) is the same as that of the first light source module (1).

[0028] Figure 3 The present invention is a structural diagram of a transceiver device of an optoelectronic integrated dual-frequency laser for coherent wind measurement, which comprises an optical amplifier (12-1), an optical circulator (12-2), and a telescope (12-3). The optical amplifier (12-1) is connected to port 1 of the optical circulator (12-2), port 2 of the optical circulator (12-2) is connected to the telescope (12-3), and port 3 of the optical circulator (12-2) is coupled to a second balanced detector (9).

[0029] Figure 4 The invention discloses a structure diagram of an optical phase-locked loop module of an optoelectronic integrated dual-frequency laser for coherent wind measurement, which comprises a circuit control chip (13-1), a frequency detector chip (13-2), and an active loop filter (13-3); the circuit control chip (13-1) realizes stable output of controlled lasers by connecting two laser chips, and connects the required reference frequency to the second input end of the frequency detector chip (13-2) through an algorithm, connects the beat frequency signal obtained by the first balanced photodetector module (8) to the first input end of the frequency detector chip (13-2) to realize frequency judgment and output phase difference signal, and filters out the high-frequency signal through the loop filter (13-3) and then connects it to the circuit control chip (13-1), and controls the laser frequency output by the DFB laser chip of the second light source module (2) with current through a specific PID control algorithm, so as to realize that the frequency difference between the two light sources is stable at a specific frequency difference.

[0030] The basic principle of the device of the present invention for coherent wind measurement is as follows:

[0031] The signal light output by the first light source module is directly irradiated on the first coupler module of the silicon photonic chip by direct coupling to couple into the silicon photonic chip. After beam splitting on the chip, one path of light is chopped by the modulator to obtain a laser with a high extinction ratio, which is output to the transceiver, and then amplified inside the transceiver and output to the atmosphere. The reference light output by the second light source module is also directly irradiated on the second coupler module of the silicon photonic chip by direct coupling to couple into the silicon photonic chip. The frequency difference of the dual light sources is obtained in real time by beating the signal after beam splitting with the first light source module, and the feedback is given to the optical phase-locked loop module to achieve phase locking and provide the parameter to the module used to process data to improve the stability and accuracy of the system. The other path is obtained by beating the echo signal collected by the transceiver after beam splitting by the beam splitter to obtain the Doppler frequency shift, and the frequency difference is processed to obtain real-time wind field information. The present invention leaves an output port vacant, and the third coupler module can realize the expansion of the applicable field. If two signal lights need to be detected at the same time, this light source can be connected to the transceiver to realize dual light source detection.

[0032] In the field of coherent wind measurement, the present invention mainly utilizes heterodyne optical phase-locked loop technology to make dual light sources produce a fixed frequency difference, and utilizes modulator cascade to form pulsed light with a high extinction ratio. Then, the Doppler wind measurement principle is utilized to acquire wind field information by acquiring signals through an acquisition card and processing the frequency shift obtained by the beat frequency of the echo signal and the reference light through software.

Claims

1. An optoelectronic integrated dual-frequency laser for coherent wind measurement, characterized in that: The invention comprises an optical phase-locked loop module (13), a first light source module (1), a second light source module (2) and a transceiver (12), as well as a first coupler module (3), a second coupler module (4), a third coupler module (11), a first beam splitter module (5), a second beam splitter module (6), a third beam splitter module (10), a modulator module (7), a first balanced photodetector module (8) and a second balanced photodetector module (9) on a chip; The optical phase-locked loop module (13) is connected to the first light source module (1) and the second light source module (2) respectively, so as to control the light output by the light source module (2) and the light output by the light source module (1) to be stable at a certain frequency difference, and to control and maintain the stable operation of the laser; The signal light output by the first light source module (1) is coupled into the optical chip through the first coupler module (3); after the signal light is split by the first beam splitter (5), the first output end of the signal light is connected to the first input end of the balanced detector module (8); the second output end is coupled to the modulator module (7), so that the signal light is modulated by the modulator module into a high extinction ratio optical pulse and coupled to the transceiver device (12) through the optical fiber; The reference light output by the second light source module (2) is coupled into the optical chip through the second coupler module (4); the signal light is split by the second beam splitter module (6), and its first output port is connected to the second input port of the first balanced photodetector module (8), so that the first balanced photodetector module (8) obtains the beat signal between the signal light and the reference light and feeds it back to the optical phase-locked loop module to achieve heterodyne phase locking; the split reference light is connected to the input end of the third beam splitter module (10) through the second output port of the second beam splitter module (6); the reference light is further split and input to the first input end of the second balanced detector module (9) through the first output end of the third beam splitter module (10); the second output end of the third beam splitter module (10) inputs the reference light to the third coupler module to output the reference light; the second balanced detector module (9) is coupled to the transceiver (12) through optical fiber to obtain the echo signal and beat the reference signal to obtain the frequency difference.

2. The optoelectronic integrated dual-frequency laser for coherent wind measurement according to claim 1, characterized in that: The first light source module (1) and the second light source module (2) both comprise a DFB laser chip, a first lens, an isolator, a polarizer, and a second lens; the light emitted by the laser chip is collimated by the first lens and then incident on the isolator, and then reaches the polarizer after passing through the isolator; the light beam after passing through the polarizer becomes linearly polarized light and is focused by the second lens.

3. The optoelectronic integrated dual-frequency laser for coherent wind measurement according to claim 1, characterized in that: The optical phase-locked loop (13) comprises a circuit control chip (13-1), a frequency detector chip (13-2), and an active loop filter (13-3); the circuit control chip (13-1) controls the stable output of laser light by connecting two laser chips, and controls the circuit control chip to output a required reference frequency through an algorithm and connects it to the second input end of the frequency detector chip (13-2); the beat frequency signal obtained by the first balanced photodetector module (8) is connected to the first input end of the frequency detector chip (13-2) to output a phase difference signal by frequency judgment, and the high-frequency signal is filtered out through the loop filter (13-3) and then connected to the circuit control chip (13-1); a control current signal is output through a specific PID control algorithm, and the laser frequency output by the DFB laser chip of the second light source module (2) is controlled by current, so that the frequency difference between the two light sources is stabilized at a specific frequency difference; the optical phase-locked loop (13) is a heterodyne digital phase lock.

4. The optoelectronic integrated dual-frequency laser for coherent wind measurement according to claim 2, characterized in that: The lasers emitted by the first light source module (1) and the second light source module (2) are continuous linear polarized light with a narrow line width, and the wavelength is in the near-infrared band that ensures the safety of human eyes.

5. The optoelectronic integrated dual-frequency laser for coherent wind measurement according to claim 1, characterized in that: The modulator module (7) is an SOA, an electro-optic modulator or an acousto-optic modulator, and achieves a high extinction ratio of pulse light in a cascaded form.

6. The optoelectronic integrated dual-frequency laser for coherent wind measurement according to claim 1, characterized in that: The first balanced photodetector module (8) and the second balanced photodetector module (9) are composed of an on-chip integrated photodetector and a silicon photonic chip external optoelectronic hybrid package transimpedance amplifier chip, and are used to convert the current signal generated by the beat frequency into a voltage signal and realize transimpedance amplification, thereby improving detection accuracy.

7. The optoelectronic integrated dual-frequency laser for coherent wind measurement according to claim 1, characterized in that: The first coupler module (3), the second coupler module (4) and the third coupler module (11) are end face couplers and may also be grating couplers or other devices used for coupling between optical fibers and chips or between chips to achieve low-loss coupling.

8. The optoelectronic integrated dual-frequency laser for coherent wind measurement according to claim 1, characterized in that: The first beam splitter module (5), the second beam splitter module (6) and the third beam splitter module (10) are Y-type beam splitters, 1*2 MMIs or directional couplers, and different beam splitting ratios can be achieved by modifying parameters.

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