CN-121984598-A - One-to-many laser communication-oriented multi-focus composite Fresnel phase diagram rapid generation and power equalization method

CN121984598ACN 121984598 ACN121984598 ACN 121984598ACN-121984598-A

Abstract

The application discloses a multi-focus composite Fresnel phase diagram rapid generation and power equalization method and system for one-to-many free space laser communication; aiming at scenes with a plurality of user targets positioned at different pointing angles and different propagation distances, the method constructs a single beam phase of 'focusing + pointing' for each target based on analyzing the phase and the linear inclined phase of the Fresnel zone lens, and takes the phase after carrying out complex field superposition according to preset power weight, thereby directly obtaining a composite phase diagram for a phase type Spatial Light Modulator (SLM). The power weight is preset according to the link budget or task requirement to realize the on-demand distribution and balance of the multi-beam output power, and simultaneously, a fixed phase bias can be introduced for each beam to inhibit inter-beam interference fringes. The application does not need to solve the iteration frame by frame, has low calculation complexity and is easy to realize the online update with high frame rate and low delay.

Inventors

YANG GUANG
YANG YUFU
LIU ZHI
YU MIAO

Assignees

长春理工大学

Dates

Publication Date: 20260505
Application Date: 20260211

Claims (7)

1. A multi-focus composite Fresnel phase diagram rapid generation and power equalization method for one-to-many laser communication is characterized by comprising the following steps: S1, acquiring space parameters of N target receiving ends, wherein the space parameters comprise the pointing angles (theta x, k, theta y, k) and the propagation distances Lk of each target, and distributing power weights wk for each target so as to meet the condition that wk is more than or equal to 0 and sigma kwk =1; s2, for each target k, constructing a Fresnel lens phase phi f, k (x, y) for focusing and a tilt phase phi t, k (x, y) for pointing, and obtaining a total phase phi k (x, y) =phi f, k (x, y) +phi t, k (x, y) +delta k of the target, wherein delta k is an optional fixed phase offset; S3, superposing the target complex fields according to the power weight to obtain complex fields E (x, y) = Σkwk exp (i.Φk (x, y)), and taking complex field phases Φ (x, y) = arg { E (x, y) } as a complex phase map; S4, carrying out 2 pi wrapping and gray scale quantization on the composite phase diagram phi (x, y), and loading the composite phase diagram phi (x, y) to a phase Spatial Light Modulator (SLM) after correction by a gray scale-phase calibration lookup table, so that incident laser forms N beams of multi-beam light which are respectively directed at different angles and converged at corresponding distances; s5, performing independent intensity modulation on each beam by adopting on-off keying OOK, wherein the OOK is realized by switching the power weight wk of the corresponding target between an on state and an off state or updating according to bit mapping, so that the receiving end of each target completes parallel data reception.
2. The method for fast generating and power balancing of a multi-focal composite fresnel phase map for one-to-many laser communication according to claim 1, wherein the fresnel lens phases Φf, k (x, y) in step S2 satisfy the following expression: φf,k(x,y)=mod{(2π/λ)·(√(f_k^2+x^2+y^2)−f_k),2π} Where λ is the operating wavelength, f_k is the equivalent focal length corresponding to the target propagation distance Lk, mod {. 2 pi } represents modulo 2pi.
3. The method for fast generating and power balancing of a multi-focal composite fresnel phase map for one-to-many laser communication according to claim 1, wherein the tilt phases Φt, k (x, y) in step S2 satisfy the following expression: φt,k(x,y)=(2π/λ)·(u_{x,k}·x+u_{y,k}·y) Wherein (u_ { x, k }, u_ { y, k }) is a spatial frequency parameter for deflecting the kth beam of light to a pointing angle (θx, k, θy, k), which is determined by optomechanical calibration or theoretical calculation.
4. The method for quickly generating and balancing the multi-focus composite fresnel phase diagram for one-to-many laser communication according to claim 1, wherein the power weight wk is preset according to a link budget to compensate for the expected receiving power difference caused by different target propagation distances, atmospheric attenuation or receiving caliber differences, so as to realize on-demand distribution and balancing of the multi-beam output power of the transmitting end without closed loop feedback of the receiving end.
5. The method for fast generating and power balancing of a multi-focal composite fresnel phase map for one-to-many laser communication according to claim 1, wherein in step S2, different fixed phase offsets δk are adopted for different targets, and δk is in the range of [0, pi/2 ], so as to reduce coherence between beams and suppress interference fringes generated by complex field superposition.
6. The method for quickly generating and balancing power of the multi-focus composite Fresnel phase diagram for one-to-many laser communication according to claim 1 is characterized in that the phase diagram is generated by adopting analytic calculation and complex field superposition to obtain phases, avoiding iterative solution frame by frame, and writing the phase diagram into an SLM by adopting a double-buffer loading mode so as to realize online updating and switching with high frame rate and low delay.
7. The multi-focus composite Fresnel phase diagram rapid generation and power equalization system for realizing the method of any one of claims 1 to 6 is characterized by comprising a laser light source, a phase type Spatial Light Modulator (SLM), a phase diagram generation and drive control module, a transmitting optical assembly and a plurality of receiving ends, wherein the phase diagram generation and drive control module is used for calculating a composite phase diagram according to a target pointing angle and a propagation distance and loading the composite phase diagram to the SLM, so that a plurality of converging lights are formed by outputting the laser light source and respectively pointing to the plurality of receiving ends, and the plurality of receiving ends comprise an optical receiving antenna and a photoelectric detector for detecting and judging an OOK modulation signal.

Description

One-to-many laser communication-oriented multi-focus composite Fresnel phase diagram rapid generation and power equalization method Technical Field The invention relates to the technical field of free space laser communication and wavefront regulation, in particular to a method and a system for rapidly generating and balancing power of a multi-focus composite Fresnel phase diagram for one-to-many laser communication. Background Free space laser communication (Free-SpaceOpticalCommunication, FSO) realizes information transmission by utilizing laser to propagate in Free space, has the advantages of large bandwidth, strong confidentiality, electromagnetic interference resistance, small antenna caliber and the like, and is suitable for the scenes of satellite-ground/inter-satellite high-speed data transmission, airborne/carrier-based platform communication, ground multi-site networking, emergency communication and the like. With the increasing demands of constellation systems, unmanned platform clusters and ground multi-terminal access, communication systems gradually develop from traditional point-to-point links to multi-point concurrency and networking, wherein a typical demand is that a single transmitting end simultaneously serves multiple receiving ends, namely 'one-to-many' laser communication. In a 'one-to-many' laser communication scene, a transmitting end needs to form a plurality of beams pointing to different users in the same time window so as to realize parallel links or multiple access of time slot polling, meanwhile, each receiving end is always in different space directions and propagation distances, dynamic factors such as relative motion, gesture jitter, distance change and the like exist, and the transmitting end needs to have flexible control capability on the pointing angle (two-dimensional angle) and wavefront focusing state (equivalent focal length/image plane position) of each beam. The "one-to-many" scenario requires not only higher angular coverage capability, but also lower crosstalk and more stable received power when multiple beams coexist to ensure communication Bit Error Rate (BER) and link availability, as compared to conventional single links. However, free space laser is affected by various factors in the propagation process, namely, the geometric diffusion caused by the propagation distance reduces the energy ratio captured by the receiving port, the aerosol, haze, precipitation and the like cause scattering and absorption to cause additional attenuation, the atmospheric turbulence causes random fluctuation of refractive index to cause light intensity flicker, wave front distortion and light beam drift (beamwander) to further cause fluctuation of receiving power with time, and the platform posture shake, structural vibration and pointing tracking error can cause light spots to deviate from the center of the receiving port view field. In an OOK equal-intensity modulation mode, a receiving end decision threshold is highly sensitive to average power and fluctuation thereof, and power drop or fluctuation increase can significantly deteriorate error rate, even cause link interruption. Therefore, in one-to-many communication, if a plurality of light beams are disturbed at the same time, power fluctuation and mutual interference thereof are superimposed and amplified, so that the stability of the system is significantly reduced. To achieve multi-beam generation and pointing control, the prior art generally employs several types of schemes: (1) Fixed beam splitting/fixed diffraction element schemes-splitting a single beam of light into multiple beams by a beam splitter, a microlens array, or a fixed Diffraction Optical Element (DOE). The scheme has the advantages of simple structure and higher optical efficiency, but the beam splitting angle and the power distribution are usually fixed, are difficult to adjust in real time according to the position change of a user, and meanwhile, when the target distance is different or focus control is required, the fixed optical structure is difficult to simultaneously meet the optimal focus requirements at different distances, so that the adaptability is insufficient. (2) Multiple lasers or array light source schemes, using multiple lasers to individually align multiple receiving ends. The scheme can realize independent control of each channel, but obviously increases the complexity, the volume weight, the power consumption and the calibration cost of the system, and has more difficult relative stability, consistency and synchronous control of multiple paths of light sources, higher engineering realization cost and adverse effect on miniaturized and low-cost terminal deployment. (3) The mechanical scanning/galvanometer scanning scheme includes fast scanning single beam with holder, turntable or galvanometer, and covering several users in time division mode. The scheme can provide angular coverage, but has the problems of mechanical inertia, bandwi