An optical phased array laser communication system based on multi-aperture coherent combination

Abstract

The present invention provides an optical phased array laser communication system based on multi-aperture coherent synthesis, including a large deflection angle optical phased array antenna, a relay optical path, a fiber phase shifter, a fiber combiner, a fiber beam splitter, a laser emission unit, a coherent demodulation unit, an optical power detection unit, and a phase control unit. The large deflection angle optical phased array antenna realizes the deflection of a light beam in a large angle range, the relay optical path realizes the tracking of the light beam and couples it to the optical fiber, and the fiber phase shifter and the fiber combiner perform coherent synthesis on the light coupled to the optical fiber via multiple aperture optical phased array antennas to enhance the optical power of the received signal. The present invention overcomes the influence of laser communication interruption caused by the large angle deflection response time of the optical phased array antenna by time-sharing control of the angle deflection of each aperture optical phased array, thereby realizing continuous and uninterrupted high-speed transmission of optical phased array laser communication in a large angle range, and can be widely used in space laser communication links such as inter-satellite, satellite-to-ground, air-to-air, and air-to-ground.

Description

Technical Field

[0001] The present invention relates to the field of communication technologies, and particularly relates to an optical phased array laser communication system based on multi-aperture coherent combination. Background Art

[0002] Compared with traditional mechanical scanning and tracking technologies, the optical phased array technology has the advantages of flexible scanning, fast deflection speed, high pointing accuracy, high spatial resolution, etc. It has broad application prospects in the fields of space laser communication, lidar, and optoelectronic countermeasure. In particular, its small size, light weight, and low power consumption make it highly favored by space laser communication systems.

[0003] At present, there are mainly various technical means for optical phased arrays, such as optical waveguides, MEMS, volume holographic gratings, birefringent prisms, fiber optic phased arrays, liquid crystal optical phased arrays, liquid crystal polarization gratings, etc. However, no matter which technical means is used, there are drawbacks that it is impossible to have a large receiving area, a wide deflection angle range, a high deflection efficiency, and a fast deflection speed at the same time, which limits the application of optical phased arrays in laser communication. Therefore, a combination of multiple technical means is adopted to achieve space laser communication. Compared with optical waveguides, MEMS, and fiber optic phased arrays, liquid crystal optical phased arrays have a large receiving area and mature technology. Therefore, liquid crystal optical phased arrays are usually combined with large-angle step deflection devices such as volume holographic gratings, birefringent prisms, and liquid crystal polarization gratings to solve the problem. In 2007, BNS in the United States and North Carolina State University (J. Buck, S. Serati, L. Hosting, et al. Polarization Gratings for Non-mechanical Beam Steering Applications, from Proceedings of the SPIE, Volume 8395, 83950F-1-6) successfully developed a liquid crystal polarization grating and achieved beam deflection within the range of ±56°; in 2006, Raytheon Company in the United States (Wide-angle beam steering system, US patent, patent number US7428100) used liquid crystal optical phased array and volume holographic grating technology to achieve continuous beam deflection within the range of ±45°; in 2012, Xiao Wenben et al. from the Institute of Optoelectronics, Chinese Academy of Sciences (Large-angle liquid crystal beam deflection system based on Wollaston prism. Optical Technology, 2012, 38(6): 588-592) used liquid crystal optical phased array and Wollaston prism to achieve continuous beam deflection within the range of ±13.25°; in 2020, Liu Xiaopeng et al. from the University of Electronic Science and Technology of China (Cascaded beam control method based on liquid crystal laser beam steering and LCPG. University of Electronic Science and Technology of China, 2020) used liquid crystal optical phased array and liquid crystal polarization grating to achieve continuous beam deflection within the range of ±13°. Due to the limitation of the response time of the above-mentioned deflection devices, the system cannot achieve continuous and stable tracking during the large-angle step deflection process, which is likely to cause the interruption of laser communication. Summary of the Invention

[0004] The present invention aims to solve the problem of laser communication interruption caused by a single-aperture large-deflection-angle optical phased array, and provides an optical phased array laser communication system based on multi-aperture coherent synthesis. By time-sharing control of the angle deflection of each aperture optical phased array, the influence of laser communication interruption caused by the response time of the large-deflection-angle optical phased array is overcome, and continuous and uninterrupted high-speed communication of the large-deflection-angle optical phased array laser communication is achieved. At the same time, the receiving area can be further expanded by splicing the receiving apertures, thereby improving the transmission distance and communication stability of the laser communication.

[0005] The present invention provides an optical phased array laser communication system based on multi-aperture coherent synthesis, comprising a large deflection angle optical phased array antenna, a relay optical path, and an optical fiber phase shifter optically connected in sequence, an optical fiber combiner and an optical fiber beam splitter connected in sequence to the output end of the optical fiber phase shifter, a coherent demodulation unit, an optical power detection unit respectively connected to the output end of the optical fiber beam splitter, and a phase control unit connected to the optical power detection unit and the optical fiber phase shifter, the number of the large deflection angle optical phased array antenna, the relay optical path, and the optical fiber phase shifter are all at least two, and all the optical fiber phase shifters are connected to the phase control unit;

[0006] The large deflection angle optical phased array antenna receives the signal beam and outputs it to the relay optical path. The relay optical path performs feedback, tracking and coupling of the beam capture into the optical fiber and then outputs it to the optical fiber phase shifter. The optical fiber phase shifter and the optical fiber combiner coherently combine the coupled light of multiple optical fibers and output it to the optical fiber splitter. The optical fiber splitter outputs part of the received optical signal to the optical power detection unit. The optical power detection unit monitors the synthesized optical power in real time and feeds back to the phase control unit according to the monitoring result. The phase control unit controls the optical fiber phase shifter to adjust the phase. The optical fiber splitter outputs the other part of the received optical signal to the coherent demodulation unit for coherent detection and information demodulation.

[0007] The optical phased array laser communication system based on multi-aperture coherent synthesis described in the present invention is, as a preferred embodiment, a large deflection angle optical phased array antenna is a large-angle deflection optical phased array antenna based on cascaded liquid crystal polarization gratings, volume Bragg gratings and birefringent prisms, a 1 / 2 wave plate controller is arranged in the large deflection angle optical phased array antenna, and each large deflection angle optical phased array antenna can be controlled in a time-sharing manner.

[0008] An optical phased array laser communication system based on multi-aperture coherent synthesis according to the present invention, as a preferred embodiment, the relay optical path includes a beam collecting system, a Faraday rotator, and a fast steering mirror sequentially arranged on the output optical path of the large deflection angle optical phased array antenna, a first beam splitter arranged on the reflected optical path of the fast steering mirror, a first polarizer, a first focusing lens, and a capture detector sequentially arranged on the reflected optical path of the first beam splitter, a second beam splitter arranged on the reflected optical path of the fast steering mirror, a second polarizer, a second focusing lens, a fine tracking detector, and a coupling collimator sequentially arranged on the reflected optical path of the second beam splitter. The second beam splitter is arranged between the first beam splitter and the coupling collimator, and the fiber optic phase shifter is arranged on the output optical path of the coupling collimator;

[0009] The signal light enters the beam collecting system for beam collection and then is output. The Faraday rotator deflects the polarization direction of the signal light by 45° and then reflects it through the fast steering mirror for beam splitting: the first part of the light passes through the first polarizer, is focused by the first focusing lens onto the capture detector, and the optical phased array laser communication system performs real-time control on the polarization state of the optical phased array beam according to the spot imaging position of the capture detector for capture and coarse tracking; the second part of the light passes through the second polarizer, is focused by the second focusing lens onto the fine tracking detector, and the optical phased array laser communication system performs real-time control on the fast steering mirror according to the spot imaging position of the fine tracking detector for fine tracking; the third part of the light is coupled to the single-mode fiber through the coupling collimator and output to the fiber optic phase shifter.

[0010] An optical phased array laser communication system based on multi-aperture coherent synthesis according to the present invention, as a preferred embodiment, the signal light received by one large deflection angle optical phased array antenna is a sub-aperture signal light. The optical phased array laser communication system receives and splices multiple sub-aperture signal lights and then performs co-phasing of the system through phase delay and controls the deflection moment of each large deflection angle optical phased array antenna;

[0011] The electric vectors of the sub-aperture signal lights are respectively:

[0012]

[0013]

[0014] ……,

[0015]

[0016] where A i is the amplitude of the i-th sub-aperture signal light, is the phase of the i-th fiber optic phase shifter, is the initial phase of the i-th sub-aperture signal light, n is the total number of sub-aperture signal lights, ω is the frequency of the signal light, and Δω is the modulation frequency of the signal light;

[0017] The optical vector E of the combined beam signal output by the fiber optic combiner is:

[0018] E(t) = E1(t) + E2(t) +... + E n (t);

[0019] The phase control unit adjusts the phase of the fiber optic phase shifter according to the optical vector E of the combined beam signal measured by the optical power detection unit so that the received beams of the large deflection angle optical phased array antenna are in phase.

[0020] In a preferred embodiment of the optical phased array laser communication system based on multi-aperture coherent combination of the present invention, the fiber optic phase shifter is a single-arm linear lithium niobate electro-optic phase modulator or a piezoelectric ceramic ring fiber optic phase modulator;

[0021] The fiber optic combiner is an N×1 single-mode fiber optic combiner, and the number of N is the same as the number of large deflection angle optical phased array antennas.

[0022] In a preferred embodiment of the optical phased array laser communication system based on multi-aperture coherent combination of the present invention, the fiber optic splitter is of a 1-to-3 structure form and the splitting ratio is 8:1:1.

[0023] In a preferred embodiment of the optical phased array laser communication system based on multi-aperture coherent combination of the present invention, the fiber optic splitter includes two series-connected 1-to-2 fiber optic splitters, and the splitting ratio of each fiber optic splitter is 9:1.

[0024] In a preferred embodiment of the optical phased array laser communication system based on multi-aperture coherent combination of the present invention, the coherent demodulation unit is matched according to the coherent modulation method at the transmitting end, and the coherent modulation signal demodulation mechanism of the coherent demodulation unit is heterodyne coherent detection or homodyne coherent detection;

[0025] The optical power detection unit is a fiber optic power meter, and the working wavelength range of the optical power detection unit covers the wavelength of the signal light;

[0026] The control algorithms used by the phase control unit include any one or more of the following: random parallel gradient algorithm, hill climbing method, multi-dither method, single-dither method, genetic algorithm, evolutionary algorithm, and neural network algorithm.

[0027] In a preferred embodiment of the optical phased array laser communication system based on multi-aperture coherent combination of the present invention, it further includes a laser emitting unit connected to the output end of the fiber optic splitter;

[0028] The optical phased array laser communication system can also perform co-phased emission of the optical phased array antennas of each aperture. The process of co-phased emission is as follows: The signal light emitted by the laser emission unit is sequentially transmitted through the fiber optic beam splitter, fiber optic combiner, fiber optic phase shifter, relay optical path, and large deflection angle optical phased array antenna in the reverse direction to the laser communication terminal of the other party.

[0029] In a preferred embodiment, the laser emission unit of the optical phased array laser communication system based on multi-aperture coherent combination of the present invention includes a transmitting laser, a modulator, and a fiber optic amplifier connected in sequence.

[0030] The transmitting laser is a fiber laser, a semiconductor laser, or a solid laser, and the transmitting laser is a single-frequency and single-mode laser light source; the modulator modulates the output light of the transmitting laser according to the communication mode and information and then outputs it to the fiber optic amplifier, and the fiber optic amplifier amplifies the laser power.

[0031] The technical solution adopted by the present invention to solve its technical problems is: An optical phased array laser communication system based on multi-aperture coherent combination, characterized by including a large deflection angle optical phased array antenna, a relay optical path, a fiber optic phase shifter, a fiber optic combiner, a fiber optic beam splitter, a laser emission unit, a coherent demodulation unit, an optical power detection unit, and a phase control unit.

[0032] The light beam passing through the large deflection angle optical phased array antenna realizes the feedback of beam capture, high-precision tracking, and high-efficiency coupling to the optical fiber by the relay optical path. The light of multiple optical fibers is coherently combined by the fiber optic phase shifter and the fiber optic combiner. The combined light is split into two by the fiber optic beam splitter: A small part of the light is transmitted through the optical fiber to the optical power detection unit to monitor the power of the combined light in real time, and the monitoring result is fed back to the phase control unit to control the fiber optic phase shifter; Most of the light is transmitted through the optical fiber to the coherent demodulation unit for coherent detection and demodulation, so as to realize the reception of the laser communication signal and the information demodulation.

[0033] The laser in the laser emission unit emits light of a corresponding wavelength band. After signal modulation by the modulator and signal enhancement by the fiber optic amplifier, it is respectively transmitted in the reverse direction to the communication target through the fiber optic beam splitter, fiber optic combiner, fiber optic phase shifter, relay optical path, and large deflection angle optical phased array system, which can ensure the co-phased emission of the optical phased array antennas of each aperture, thereby realizing the modulation and emission of the laser communication signal.

[0034] Furthermore, the large deflection angle optical phased array antenna is a large angle deflection optical phased array antenna based on a cascaded liquid crystal polarization grating, a volume Bragg grating, or a birefringent prism. When the light beam deflects at a large angle, due to the existence of the system response time, the received signal optical power will be interrupted for a short time.

[0035] Further, the relay optical path includes a beam convergence system, a Faraday rotator (optional according to requirements), a fast steering mirror, a beam splitter 1, a polarizer 1, a focusing lens 1, a capture detector, a beam splitter 2, a polarizer 2, a focusing lens 2, a fine tracking detector, and a coupling collimator;

[0036] The signal light passing through the optical phased array antenna with a large deflection angle is appropriately converged by the beam convergence system to meet the usage requirements of the small-size and high-bandwidth fast steering mirror. If necessary, the polarization direction of the converged light is deflected by 45° through the Faraday rotator. Then, after being reflected by the fast steering mirror, it is split twice: the first split separates a small part of the light that passes through the polarizer and is converged by the focusing lens to the capture detector, and the polarization state of the optical phased array beam is controlled in real time according to the spot imaging position to achieve system capture and coarse tracking. The second split separates a small part of the light that passes through the polarizer and is converged by the focusing lens to the fine tracking detector, and the fast steering mirror is controlled in real time according to the spot imaging position to achieve fine tracking of the system. Most of the remaining light is coupled into a single-mode fiber through the coupling collimator.

[0037] Further, the fiber phase shifter is a single-arm linear lithium niobate electro-optic phase modulator, a piezoelectric ceramic ring fiber phase modulator, or other phase modulators.

[0038] Further, the fiber combiner is an N×1 single-mode fiber combiner, and the number of N is determined by the number of apertures of the optical phased array.

[0039] Further, the fiber splitter has a 1-to-3 structure form, and the splitting ratio is about 8:1:1; or it is composed of two series-connected 1-to-2 fiber splitters, and the splitting ratio is about 9:1.

[0040] Further, the laser emission unit includes a transmitting laser, a modulator, and a fiber amplifier. The transmitting laser is a fiber laser, a semiconductor laser, a solid-state laser, or other lasers, and should be a single-frequency and single-mode laser source. The modulator modulates the light emitted by the laser according to the communication method and information, and the modulated light is amplified to the required optical power by the fiber amplifier.

[0041] Further, the coherent demodulation unit can be matched according to the coherent modulation method at the transmitting end, and can be various coherent modulation signal demodulation mechanisms such as heterodyne and homodyne coherent detection.

[0042] Further, the optical power detection unit is a fiber optic power meter, or a combination of a fiber collimator and a photodetector. The working wavelength range of the power meter and the photodetector should cover the wavelength of the signal light.

[0043] Furthermore, the control algorithms used by the phase control unit include, but are not limited to, stochastic parallel gradient algorithm, hill climbing method, multi-dithering method, single-dithering method, genetic algorithm, evolutionary algorithm, neural network algorithm, etc.

[0044] The principle of the present invention can be described as follows: Large deflection angle optical phased array antennas usually control the polarization state of the light beam (left-handed and right-handed circularly polarized light, S light and P light of linearly polarized light) to cause large-angle deflection of the light beam. When switching the polarization state of the light beam, due to the existence of the switching time (material response time), it brings about a short interruption of the light beam, thus causing an interruption in laser communication. After adopting the multi-aperture splicing method, the co-phase of the system is realized through phase delay for each aperture, and the large-angle deflection moment of each aperture is reasonably controlled (time-sharing control). When the signal light of one sub-aperture is interrupted, other sub-apertures can work normally, thus realizing uninterrupted high-speed communication of the system.

[0045] Since most phased array antennas have the requirement of the same polarization characteristic for the received and transmitted light beams, a Faraday rotator is added in the relay optical path to realize polarization isolation of the received and transmitted light beams. The Faraday rotator uses a magneto-optical effect crystal. When a magnetic field in a certain direction is applied, it will cause a change in the polarization state of the light passing through the crystal. This change is related to the material itself, related to the direction of the applied magnetic field and the incident angle, and independent of the light propagation direction. A Faraday rotator with a polarization direction deflected by 45° is adopted. The transmitted light beam is incident from side A and exits from side B, with the polarization direction deflected by 45°. The received light beam is incident from side B and exits from side A, with the polarization direction also deflected by 45°. The polarization states of the received and transmitted light beams are the same on side A, so the polarization states of the received and transmitted light beams on side B differ by 90°, thus realizing the isolation of the receiving and transmitting polarization states.

[0046] The spatial light passing through the multi-aperture optical phased array is respectively coupled into single-mode optical fibers through the relay optical path, and coherent beam combination is carried out by an optical fiber phase shifter and an optical fiber combiner. Since it comes from the same laser emission source, the optical wave electric vectors of each sub-aperture before beam combination are

[0047]

[0048]

[0049] ……

[0050]

[0051] In the formula, A i , Δω i , are respectively the amplitude of the signal light from the i-th aperture, the phase of the optical fiber phase shifter, and the initial phase (related to the path optical path); ω and Δω are the frequency and modulation frequency of the signal light. The electric vector of the synthesized signal light is

[0052] E(t)=E1(t)+E2(t)+L+E n (t)

[0053] The intensity of the combined light reaches its maximum value only when and only when the photoelectric vectors of each signal are in phase. When the light intensity in the fiber is the highest after the beam is combined. The combined light is split by the fiber beam splitter, and a small part of the light (about 10% of the energy) is sent to the optical power meter (or photodetector). When the light intensity measured by the optical power meter is the strongest, the light reaching the coherent demodulation unit is also the strongest. The phase of the fiber delayer can be adjusted quickly by using control algorithms such as the random descent parallel gradient algorithm (SPGD).

[0054] The present invention has the following advantages:

[0055] (1) The present invention adopts a multi-aperture coherent synthesis method to achieve the co-phase synthesis of light beams from different optical phased array antennas. By controlling the large-angle deflection of the optical phased array in a time-sharing manner, communication interruption caused by the large-angle deflection process can be avoided, and continuous and uninterrupted communication within a large angle range of large-aperture optical phased array antennas can be achieved, thereby expanding the application scenarios of optical phased arrays in the field of laser communications.

[0056] (2) The present invention adopts a multi-aperture coherent synthesis method, which can realize the splicing of multi-aperture antennas to increase the effective receiving area of ​​the optical phased array, improve the working distance of the optical phased array laser communication and the link margin of the space laser link, and make the optical phased array practical in the field of laser communication.

[0057] (3) The present invention adopts a multi-aperture coherent synthesis method, which does not have very strict requirements on the antenna orientation and installation position of the spliced ​​aperture. It can be designed according to the loading platform, greatly improving the platform adaptability of the laser communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a block diagram of an optical phased array laser communication system based on multi-aperture coherent synthesis;

[0059] Figure 2 The present invention is a block diagram of the components of the relay optical path part of an optical phased array laser communication system based on multi-aperture coherent synthesis;

[0060] Figure 3 The present invention is a block diagram of the laser emission unit of an optical phased array laser communication system based on multi-aperture coherent synthesis.

[0061] Reference numerals:

[0062] 1. Large deflection angle optical phased array antenna; 2. Relay optical path; 21. Beam convergence system; 22. Faraday rotator; 23. Fast steering mirror; 24. First beam splitter; 25. First polarizer; 26. First focusing lens; 27. Acquisition detector; 28. Second beam splitter; 29. Second polarizer; 2a. Second focusing lens; 2b. Fine tracking detector; 2c. Coupling collimator; 3. Fiber optic phase shifter; 4. Fiber optic combiner; 5. Fiber optic splitter; 6. Coherent demodulation unit; 7. Optical power detection unit; 8. Phase control unit; 9. Laser emission unit; 91. Emission laser; 92. Modulator; 93. Fiber optic amplifier; Detailed implementation mode

[0063] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0064] Embodiment 1

[0065] As Figure 1 shown, an optical phased array laser communication system based on multi-aperture coherent synthesis includes a large deflection angle optical phased array antenna 1, a relay optical path 2, and a fiber optic phase shifter 3 that are optically connected in sequence. A fiber optic combiner 4 and a fiber optic splitter 5 are sequentially connected to the output end of the fiber optic phase shifter 3. A coherent demodulation unit 6 and an optical power detection unit 7 are respectively connected to the output end of the fiber optic splitter 5. A phase control unit 8 is connected to both the optical power detection unit 7 and the fiber optic phase shifter 3, and a laser emission unit 9 is connected to the output end of the fiber optic splitter 5. The number of the large deflection angle optical phased array antenna 1, the relay optical path 2, and the fiber optic phase shifter 3 is at least two, and all the fiber optic phase shifters 3 are connected to the phase control unit 8;

[0066] After receiving the signal beam, the large deflection angle optical phased array antenna 1 outputs it to the relay optical path 2. The relay optical path 2 performs feedback, tracking of beam acquisition, and couples it into the optical fiber and then outputs it to the fiber optic phase shifter 3. The fiber optic phase shifter 3 and the fiber optic combiner 4 perform coherent synthesis on the coupled light of multiple optical fibers and then output it to the fiber optic splitter 5. The fiber optic splitter 5 outputs a part of the received optical signal to the optical power detection unit 7. The optical power detection unit 7 monitors the synthesized optical power in real time and feeds back the monitoring result to the phase control unit 8. The phase control unit 8 controls the fiber optic phase shifter 3 to perform phase adjustment. The fiber optic splitter 5 outputs another part of the received optical signal to the coherent demodulation unit 6 for coherent detection and information demodulation;

[0067] The large deflection angle optical phased array antenna 1 is a large-angle deflection optical phased array antenna based on a cascaded liquid crystal polarization grating, a volume Bragg grating and a birefringent prism. A 1 / 2 wave plate controller is provided in the large deflection angle optical phased array antenna 1, and each large deflection angle optical phased array antenna 1 can be controlled in a time-sharing manner;

[0068] like Figure 2 As shown, the relay optical path 2 includes a focusing system 21, a Faraday rotator 22, and a fast reflector 23 which are sequentially arranged on the output optical path of the large deflection angle optical phased array antenna 1, a first beam splitter 24 which is arranged on the reflected optical path of the fast reflector 23, a first polarizer 25, a first converging lens 26, and a capture detector 27 which are sequentially arranged on the reflected optical path of the first beam splitter 24, a second beam splitter 28 which is arranged on the reflected optical path of the fast reflector 23, a second polarizer 29, a second converging lens 2a, a precision tracking detector 2b which are sequentially arranged on the reflected optical path of the second beam splitter 28, and a coupling collimator 2c which is arranged on the reflected optical path of the fast reflector 23, the second beam splitter 28 is arranged between the first beam splitter 24 and the coupling collimator 2c, and the optical fiber phase shifter 3 is arranged on the output optical path of the coupling collimator 2c;

[0069] The signal light enters the focusing system 21 for focusing and then output. The Faraday rotator 22 deflects the polarization direction of the signal light by 45° and then reflects it through the fast reflector 23 for further splitting: the first part of the light passes through the first polarizer 25 and is converged to the capture detector 27 through the first converging lens 26. The optical phased array laser communication system controls the polarization state of the optical phased array light beam in real time according to the imaging position of the light spot of the capture detector 27 for capturing and coarse tracking; the second part of the light passes through the second polarizer 29 and is converged to the fine tracking detector 2b through the second converging lens 2a. The optical phased array laser communication system controls the fast reflector 23 in real time according to the imaging position of the light spot of the fine tracking detector 2b for fine tracking; the third part of the light is coupled to the single-mode optical fiber through the coupling collimator 2c and output to the optical fiber phase shifter 3;

[0070] The signal light received by a large deflection angle optical phased array antenna 1 is a sub-aperture signal light. The optical phased array laser communication system receives and splices multiple sub-aperture signal lights, performs system co-phasing through phase delay, and controls the deflection moment of each large deflection angle optical phased array antenna 1.

[0071] The electric vectors of the sub-aperture signal light are:

[0072]

[0073]

[0074] ...,

[0075]

[0076] Among them, A i is the amplitude of the i-th sub-aperture signal light, is the phase of the i-th fiber optic phase shifter 3, is the initial phase of the i-th sub-aperture signal light, n is the total number of sub-aperture signal lights, ω is the frequency of the signal light, and Δω is the modulation frequency of the signal light;

[0077] The optical electric vector Et of the combined beam signal output by the fiber optic combiner 4 is:

[0078] E(t) = E1(t) + E2(t) +... + E n (t);

[0079] The phase control unit 8 adjusts the phase of the fiber optic phase shifter 3 according to the optical electric vector Et of the combined beam signal measured by the optical power detection unit 7 so that the received light beams of the large deflection angle optical phased array antenna 1 are in phase;

[0080] The fiber optic phase shifter 3 is a single-arm linear lithium niobate electro-optic phase modulator or a piezoelectric ceramic ring fiber optic phase modulator;

[0081] The fiber optic combiner 4 is an N×1 single-mode fiber optic combiner, and the number of N is the same as the number of the large deflection angle optical phased array antennas 1;

[0082] The fiber optic splitter 5 has a 1-to-3 structure and a splitting ratio of 8:1:1;

[0083] The fiber optic splitter 5 includes two series-connected 1-to-2 fiber optic splitters, and the splitting ratio of each fiber optic splitter is 9:1;

[0084] The coherent demodulation unit 6 is matched according to the coherent modulation method at the transmitting end, and the coherent modulation signal demodulation mechanism of the coherent demodulation unit 6 is heterodyne coherent detection or homodyne coherent detection;

[0085] The optical power detection unit 7 is a fiber optic power meter, and the working wavelength range of the optical power detection unit 7 covers the wavelength of the signal light;

[0086] The control algorithms used by the phase control unit 8 include any one or more of the following: random parallel gradient algorithm, hill climbing method, multi-dither method, single-dither method, genetic algorithm, evolutionary algorithm, and neural network algorithm;

[0087] The optical phased array laser communication system can also perform in-phase emission of each aperture optical phased array antenna. The process of in-phase emission is as follows: The signal light emitted by the laser emission unit 9 is sequentially transmitted through the fiber optic splitter 5, fiber optic combiner 4, fiber optic phase shifter 3, relay optical path 2, and large deflection angle optical phased array antenna 1 in the reverse direction to the other laser communication terminal;

[0088] Such asFigure 3 As shown, the laser emission unit 9 includes a transmitting laser 91, a modulator 92, and an optical fiber amplifier 93 that are connected in sequence.

[0089] The transmitting laser 91 is a fiber laser, a semiconductor laser, or a solid-state laser, and the transmitting laser 91 is a single-frequency and single-mode laser light source; the modulator 92 modulates the light output by the transmitting laser 91 according to the communication mode and information and then outputs it to the optical fiber amplifier 93, and the optical fiber amplifier 93 amplifies the laser power.

[0090] Embodiment 2

[0091] As Figure 1 As shown, an optical phased array laser communication system based on multi-aperture coherent combination includes a large-deflection-angle optical phased array antenna 1, a relay optical path 2, an optical fiber phase shifter 3, an optical fiber combiner 4, an optical fiber splitter 5, a coherent demodulation unit 6, an optical power detection unit 7, a phase control unit 8, and a laser emission unit 9.

[0092] For the light beam passing through the large-deflection-angle optical phased array antenna 1, the relay optical path 2 realizes the feedback of beam capture, high-precision tracking, and high-efficiency coupling to the optical fiber, and the optical fiber phase shifter 3 and the optical fiber combiner 4 are used to coherently combine the light of multiple optical fibers. The combined light is split into two by the optical fiber splitter 5: a small part of the light is transmitted through the optical fiber to the optical power detection unit 7 to monitor the power of the combined light in real time, and the monitoring result is fed back to the phase control unit 8 to control the optical fiber phase shifter 3; most of the light is transmitted through the optical fiber to the coherent demodulation unit 6 for coherent detection and information demodulation.

[0093] According to the principle of optical path reversibility, the signal light emitted by the laser emission unit 9 is reversely emitted to the communication target through the optical fiber splitter 5, the optical fiber combiner 4, the optical fiber phase shifter 3, the relay optical path 2, and the large-deflection-angle optical phased array antenna 1.

[0094] In this embodiment, the optical phased array antenna is composed of 4 aperture antennas. Each antenna uses a cascaded liquid crystal polarization grating, the size of the cascaded liquid crystal polarization grating is 40mm×40mm, and it is composed of 12 layers of liquid crystal polarization gratings. A 1 / 2 wave plate controller is added in front of each layer of liquid crystal polarization grating to control the polarization state of the incident light, realize the control of different deflection directions, and can realize the beam deflection within the range of ±45°, and the applicable wavelength range is 1550nm±2nm.

[0095] As Figure 2As shown in the figure, in this embodiment, the magnification of the beam convergence system 21 in the relay optical path 2 is 3:1; the Faraday rotator 22 rotates the vibration direction of the incident linearly polarized light by 45°; the fast steering mirror 23 is an FSM-40 with a lens diameter of 25 mm, a stroke range of ±1.5°, a closed-loop bandwidth of 500 Hz, and a resolution of 1 μrad; the beam splitting ratios of the first beam splitter 24 and the second beam splitter 28 are both 1:9, with 10% reflection and 90% transmission; the first polarizer 25 and the second polarizer 29 are used to isolate the transmitted beam, with an extinction ratio > 1000:1; the acquisition detector 27 is an infrared focal plane device with a working wavelength of 900 nm to 1700 nm; the fine tracking detector 2b is a quadrant detector with a working wavelength of 1200 nm to 1700 nm; the coupling collimator 2c is of the model F810FC-1550, with NA = 0.24 and f = 37 mm.

[0096] The signal light passing through the large deflection angle optical phased array antenna 1 is converged by the beam convergence system 21 to meet the usage requirements of a small-size, high-bandwidth fast steering mirror. The converged light is deflected by 45° in the polarization direction by the Faraday rotator 22. Then, after being reflected by the fast steering mirror 23, it is split twice: the first splitting divides a small part of the light that passes through the first polarizer 25 and is converged by the first focusing lens 26 to the acquisition detector 27, and the polarization state of the optical phased array beam is controlled in real time according to the spot imaging position of the acquisition detector 27 to achieve system acquisition. The second splitting divides a small part of the light that passes through the second polarizer 29 and is converged by the second focusing lens 2a to the fine tracking detector 2b, and the fast steering mirror 23 is controlled in real time according to the spot imaging position of the fine tracking detector 2b to achieve the fine tracking of the system. Most of the remaining light is coupled into a single-mode fiber through the coupling collimator 2c.

[0097] In this embodiment, the fiber optic phase shifter 3 is a single-arm linear lithium niobate electro-optic phase modulator.

[0098] In this embodiment, the fiber optic combiner 4 is a 4×1 single-mode fiber optic combiner.

[0099] In this embodiment, the fiber optic splitter 5 is composed of two 1×2 fiber optic splitters connected in series. The first fiber optic splitter is a polarization splitter that separates the transmitted light from the received light, and the second fiber optic splitter divides the received light into two parts with a beam splitting ratio of 9:1, and most of the light energy enters the coherent receiving unit.

[0100] As Figure 3As shown, in this embodiment, the laser emission unit 9 includes a transmitting laser 91, a modulator 92, and an optical fiber amplifier 93. The transmitting laser 91 is an external cavity semiconductor laser, which has the advantages of good stability, high conversion efficiency, small size, and good adaptability to the space environment. The working center wavelength of the laser can be set at two points: 1550.12 nm and 1550.92 nm; the modulator 92 is an IQ modulator, which modulates the light emitted by the laser to generate a BPSK laser communication signal; the working wavelength of the optical fiber amplifier 93 is 1540 nm to 1560 nm, and the output power is continuously adjustable from 200 mW to 2.5 W, and the noise figure is better than 6.5 dB.

[0101] In this embodiment, the coherent demodulation unit 6 performs coherent mixing of the received signal light and the local oscillator light in an optical mixer. The mixed optical signal is incident on a balanced detector, and the balanced detector converts the optical signal into an electrical signal, and the electrical signal is sent to the modulation and demodulation unit to complete data demodulation.

[0102] In this embodiment, the optical power detection unit 7 is a GT322D type pigtail InGaAs photodetector, with a spectral response range of 900 nm to 1700 nm and a responsivity ≥ 90% @ 1550 nm.

[0103] In this embodiment, the control algorithm used by the phase control unit 8 is the stochastic parallel gradient algorithm.

[0104] As mentioned above, the above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. An optical phased array laser communication system based on multi-aperture coherent combination, characterized in that: The invention comprises a large deflection angle optical phased array antenna (1), a relay optical path (2), and an optical fiber phase shifter (3) optically connected in sequence, an optical fiber combiner (4) and an optical fiber beam splitter (5) connected in sequence to the output end of the optical fiber phase shifter (3), a coherent demodulation unit (6), an optical power detection unit (7) respectively connected to the output end of the optical fiber beam splitter (5), and a phase control unit (8) connected to both the optical power detection unit (7) and the optical fiber phase shifter (3), wherein the number of the large deflection angle optical phased array antenna (1), the relay optical path (2), and the optical fiber phase shifter (3) is at least two, and all the optical fiber phase shifters (3) are connected to the phase control unit (8); The large deflection angle optical phased array antenna (1) receives the signal beam and outputs it to the relay optical path (2). The relay optical path (2) performs feedback, tracking and coupling of the beam capture into the optical fiber and then outputs it to the optical fiber phase shifter (3). The optical fiber phase shifter (3) and the optical fiber combiner (4) perform coherent synthesis of the coupled light of multiple optical fibers and then output it to the optical fiber beam splitter (5). The optical fiber beam splitter (5) outputs part of the received optical signal to the optical power detection unit (7). The optical power detection unit (7) monitors the synthesized optical power in real time and feeds back the monitoring result to the phase control unit (8). The phase control unit (8) controls the optical fiber phase shifter (3) to adjust the phase. The optical fiber beam splitter (5) outputs another part of the received optical signal to the coherent demodulation unit (6) for coherent detection and information demodulation. The large deflection angle optical phased array antenna (1) is a large-angle deflection optical phased array antenna based on a cascaded liquid crystal polarization grating, a volume Bragg grating and a birefringent prism. A 1 / 2 wave plate controller is provided in the large deflection angle optical phased array antenna (1), and each large deflection angle optical phased array antenna (1) can be controlled in a time-sharing manner. The relay optical path (2) comprises a focusing system (21), a Faraday rotator (22), and a fast reflector (23) which are sequentially arranged on the output optical path of the large deflection angle optical phased array antenna (1); a first beam splitter (24) which is arranged on the reflected optical path of the fast reflector (23); a first polarizer (25), a first converging lens (26), and a capture detector (27) which are sequentially arranged on the reflected optical path of the first beam splitter (24); a second beam splitter (28) which is arranged on the reflected optical path of the fast reflector (23); a second polarizer (29), a second converging lens (2a), a precision tracking detector (2b) which are sequentially arranged on the reflected optical path of the second beam splitter (28); and a coupling collimator (2c) which is arranged on the reflected optical path of the fast reflector (23); the second beam splitter (28) is arranged between the first beam splitter (24) and the coupling collimator (2c); and the optical fiber phase shifter (3) is arranged on the output optical path of the coupling collimator (2c); The signal light enters the beam collecting system (21) for beam collection and then is output. The Faraday rotator (22) deflects the polarization direction of the signal light by 45°, and then the signal light is reflected by the fast steering mirror (23) and split: The first part of the light passes through the first polarizer (25), is focused by the first focusing lens (26) onto the acquisition detector (27), and the optical phased array laser communication system performs real-time control on the polarization state of the optical phased array beam according to the spot imaging position of the acquisition detector (27) for acquisition and coarse tracking; The second part of the light passes through the second polarizer (29), is focused by the second focusing lens (2a) onto the fine tracking detector (2b), and the optical phased array laser communication system performs real-time control on the fast steering mirror (23) according to the spot imaging position of the fine tracking detector (2b) for fine tracking; The third part of the light is coupled to a single-mode fiber through the coupling collimator (2c) and output to the fiber phase shifter (3).

2. The optical phased array laser communication system based on multi-aperture coherent combination according to claim 1, wherein: The signal light received by one of the large deflection angle optical phased array antennas (1) is a sub-aperture signal light. The optical phased array laser communication system receives and splices multiple sub-aperture signal lights, performs co-phasing of the system through phase delay, and controls the deflection moment of each large deflection angle optical phased array antenna (1). The electric vectors of the sub-aperture signal lights are respectively: Among them, A i is the amplitude of the i-th sub-aperture signal light, is the phase related to the i-th fiber optic phase shifter (3), is the initial phase of the i-th sub-aperture signal light, n is the total number of the sub-aperture signal lights, ω is the frequency of the signal light, and Δω is the modulation frequency of the signal light; The electric vector E(t) of the combined beam signal output by the fiber combiner (4) is: E(t) = E1(t) + E2(t) + … + E n (t); The phase control unit (8) adjusts the phase of the fiber phase shifter (3) according to the electric vector E(t) of the combined beam signal measured by the optical power detection unit (7) so that the receiving beams of the large deflection angle optical phased array antennas (1) are co-phased.

3. An optical phased array laser communication system based on multi-aperture coherent synthesis according to claim 1, characterized in that: The fiber phase shifter (3) is a single-arm linear lithium niobate electro-optic phase modulator or a piezoelectric ceramic ring fiber phase modulator; The fiber combiner (4) is an N×1 single-mode fiber combiner, and the number of N is the same as the number of the large deflection angle optical phased array antennas (1).

4. An optical phased array laser communication system based on multi-aperture coherent combination according to claim 1, characterized in that: The fiber splitter (5) has a 1-to-3 structure form with a splitting ratio of 8:1:

1.

5. An optical phased array laser communication system based on multi-aperture coherent synthesis according to claim 1, characterized in that: The fiber splitter (5) includes two series-connected 1-to-2 fiber splitters, and the splitting ratio of each fiber splitter is 9:

1.

6. The optical phased array laser communication system based on multi-aperture coherent combination according to claim 1, wherein: The coherent demodulation unit (6) is matched according to the coherent modulation method at the transmitting end, and the coherent modulation signal demodulation mechanism of the coherent demodulation unit (6) is heterodyne coherent detection or homodyne coherent detection; The optical power detection unit (7) is a fiber optic power meter, and the working wavelength range of the optical power detection unit (7) covers the wavelength of the signal light; The control algorithms used by the phase control unit (8) include any one or more of the following: random parallel gradient algorithm, hill climbing method, multi-dither method, single-dither method, genetic algorithm, evolutionary algorithm, and neural network algorithm.

7. An optical phased array laser communication system based on multi-aperture coherent combination according to claim 1, characterized in that: It further includes a laser emitting unit (9) connected to the output end of the fiber splitter (5); The optical phased array laser communication system can also perform co-phase emission of the optical phased array antennas of each aperture. The process of the co-phase emission is as follows: The signal light emitted by the laser emission unit (9) is sequentially reversely emitted to the laser communication terminal of the other party through the optical fiber splitter (5), the optical fiber combiner (4), the optical fiber phase shifter (3), the relay optical path (2), and the large deflection angle optical phased array antenna (1).

8. An optical phased array laser communication system based on multi-aperture coherent combination according to claim 7, characterized in that: The laser emission unit (9) includes a transmitting laser (91), a modulator (92), and an optical fiber amplifier (93) connected in sequence. The transmitting laser (91) is a fiber laser, a semiconductor laser, or a solid laser, and the transmitting laser (91) is a single-frequency and single-mode laser light source; the modulator (92) modulates the output light of the transmitting laser (91) according to the communication mode and information and then outputs it to the optical fiber amplifier (93), and the optical fiber amplifier (93) amplifies the laser power.

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