CN-122027035-A - Reverse modulation optical signal self-adaptive judgment method, device and laser communication system

CN122027035ACN 122027035 ACN122027035 ACN 122027035ACN-122027035-A

Abstract

The invention discloses a self-adaptive judgment method and device for a reverse modulation optical signal and a laser communication system, which are used for solving the problems of higher error rate and the like of the existing judgment method. The method comprises the steps of setting the length and initial position of a sliding window, calculating an initialization threshold value, judging all signals in the sliding window at the initial position in sequence according to the initialization threshold value, storing signals judged to be high level into a high level one-dimensional array, storing signals judged to be low level into a non-high level one-dimensional array, storing judgment results of all high level signals and corresponding time sequence information into a first high level two-dimensional array, storing judgment results of all low level signals and corresponding time sequence information into a non-high level two-dimensional array, updating an adaptive threshold value, sequentially completing judgment of all signals, carrying out secondary judgment on all signals in the non-high level two-dimensional array, and finally combining all judged two-dimensional arrays according to the corresponding time sequence information to obtain a final judgment result.

Inventors

ZHENG YUNQIANG
GUO CHENYANG
LI GUANGYING
BIAN YIMING
LI KE
WANG WEI
SHAO XIAOPENG

Assignees

中国科学院西安光学精密机械研究所

Dates

Publication Date: 20260512
Application Date: 20260415

Claims (9)

1. The self-adaptive judgment method for the reverse modulation optical signal is used for demodulating a signal received by an active communication end in a full-duplex reverse reflection modulation laser communication system, wherein the signal is a modulation signal sent by a passive communication end, and is characterized by comprising the following steps of: step 1, setting the length and the initial position of a sliding window, and taking the average value of all signal level values in the sliding window at the initial position as an initialization threshold value; Step 2, judging all signals in the sliding window at the initial position in sequence according to the initialization threshold value, if the level value of the signals is more than or equal to the initialization threshold value, judging the signals to be high level, otherwise, judging the signals to be low level; Step 3, storing the signals judged as high level in the step 2 into a high level one-dimensional array, and storing the signals judged as low level into a non-high level one-dimensional array; Step 4, calculating to obtain a threshold updating parameter based on the level values of all signals in the high-level one-dimensional array and the non-high-level one-dimensional array in the step 3, then moving a sliding window, and combining the threshold updating parameter with the level value of the signal newly entering the sliding window to obtain a self-adaptive threshold; step 5, judging the signal which newly enters the sliding window according to the self-adaptive threshold value, judging the signal to be high level and storing the signal into the high level one-dimensional array if the level value of the signal is larger than or equal to the self-adaptive threshold value, otherwise judging the signal to be low level and storing the signal into the non-high level one-dimensional array; step 6, sequentially completing the judgment of all received signals according to the methods from step 4 to step 5; Step 7, performing secondary judgment on all signals in the non-high-level two-dimensional array according to the methods from step 1 to step6 to obtain a second high-level two-dimensional array and a low-level two-dimensional array; And 8, combining the first high-level two-dimensional array, the second high-level two-dimensional array and the low-level two-dimensional array according to the corresponding time sequence information to obtain a final binarization judgment result, thereby completing the self-adaptive judgment of the reverse modulation optical signal.
2. The method for adaptively deciding a reverse modulated optical signal according to claim 1, wherein: in step 1, the length of the sliding window is the time length of M signals, and the value range of M is 53-57.
3. The method for adaptively deciding a reverse modulated optical signal according to claim 1, wherein: In step 3, the decision result of the high level signal is 1, and the decision result of the low level signal is 0.
4. The method for adaptively determining a reverse modulation optical signal according to claim 1, wherein step 4 specifically comprises: 4.1, calculating to obtain a threshold updating parameter according to the level values of all signals in the high-level one-dimensional array and the non-high-level one-dimensional array obtained in the step 3, wherein the threshold updating parameter comprises a peak-to-peak value V pp and a window center value Variance maximum Var max ; Wherein, peak-to-peak value V pp , window center value The variance maximum value Var max is the maximum value of the variance of the high-level one-dimensional array and the variance of the non-high-level one-dimensional array; 4.2, moving the sliding window, and calculating the level value of the signal newly entering the sliding window And the window center value obtained in the step 4.1 Is the difference of (2) Wherein i represents the sequence number of the signal; 4.3, based on the peak-to-peak value V pp and variance maximum Var max obtained in step 4.1, for the difference described in step 4.2 And (3) judging: When (when) When then adaptive threshold , Is an adaptive adjustment factor, and , Representing the variance of the one-dimensional array of high levels, Representing the average value of the high-level one-dimensional array; When (when) And delta >0, then the threshold is adapted ; When (when) And delta <0, then the threshold is adapted ; In the rest of the cases, adaptive threshold 。
5. The method for adaptively determining a reverse modulated optical signal as defined in claim 4, wherein: In step 4.2, the moving the sliding window means that the current first signal in the sliding window is moved out, and the signal adjacent to the last signal enters the sliding window.
6. A reverse modulation optical signal adaptive decision device comprising a memory, a processor and a computer program stored on the memory, characterized in that the processor executes the computer program for implementing the steps of the reverse modulation optical signal adaptive decision method according to any one of claims 1 to 5.
7. The laser communication system comprises an active communication end and a passive communication end, wherein the active communication end comprises a main control module, a laser emission module, an active receiving module (4), a first detector and a first processing module, and the passive communication end comprises a spectroscope (2), a second detector, a second processing module and a reverse reflection modulation module; The laser emission module is connected with the main control module, the main control module controls the laser emission module to emit a signal beam and a question beam to the spectroscope (2) simultaneously, the signal beam is received by the second detector after being reflected by the spectroscope (2) and converted into an electric signal and then transmitted to the second processing module for signal demodulation, the question beam is transmitted by the spectroscope (2) and then enters the reverse reflection modulation module for modulation and then is transmitted, the question beam is received by the active receiving module (4) and transmitted to the first detector, and the modulated question beam is converted into a signal to be processed by the first detector and then transmitted to the first processing module, and the laser emission module is characterized in that: The first processing module adopts the reverse modulation optical signal self-adaptive judging device as claimed in claim 6, and is used for demodulating, self-adaptively judging and outputting the received signal to be processed.
8. The laser communication system of claim 7, wherein: The retroreflection modulation module comprises a pyramid prism array (3), an acousto-optic modulator and a driving control module, wherein the pyramid prism array (3) is positioned on a transmission light path of the spectroscope (2), the acousto-optic modulator is positioned at a light emitting end of the pyramid prism array (3) and is connected with the driving control module, and the driving control module is used for controlling the acousto-optic modulator to modulate and send out received interrogation light beams.
9. The laser communication system of claim 8, wherein: the size of the acousto-optic modulator is 93.0mm 23.0mm 11.0Mm, power consumption of 0.4W, and driving frequency of the radio frequency signal of 80MHz.

Description

Reverse modulation optical signal self-adaptive judgment method, device and laser communication system Technical Field The invention relates to a signal demodulation method for wireless optical communication, in particular to a self-adaptive judgment method and device for receiving a signal by an active communication end in a reverse reflection modulation laser communication system and the laser communication system. Background The wireless optical communication (FREE SPACE Optical Communication, FSOC) technology has been attracting attention in long-distance high-speed data transmission because of its advantages of high communication rate, large communication capacity, strong anti-interference capability, etc. However, conventional wireless optical communication systems typically require the deployment of complex and precise pointing and tracking devices at the transmitting and receiving ends to ensure accurate alignment of the light beam. This requirement makes the wireless optical communication system bulky, high in power consumption, poor in deployment flexibility, and difficult to integrate into a miniaturized and lightweight mobile platform such as an unmanned aerial vehicle and a portable terminal. To solve this problem, the technology of retroreflective modulation has been developed and has gradually become an important branch of wireless optical communication. The technology is characterized in that a passive communication end (such as an unmanned aerial vehicle and a microsatellite) does not need to be provided with an active tracking and light beam pointing device. In contrast, the optical element (such as a cat eye optical system or a reflecting prism) with a reverse reflection characteristic is utilized to modulate the received incident light signal and then reflect the modulated incident light signal back to the active communication end along the original path. The method greatly simplifies the structure of the passive communication terminal, remarkably reduces the size, the weight and the power consumption (SWaP), and is particularly suitable for dynamic scenes such as unmanned aerial vehicle to-ground communication, unmanned aerial vehicle inter-cluster communication, inter-satellite/satellite laser communication and the like. In a reverse reflection modulation laser communication system, especially in a full duplex communication mode, a signal beam received by an active communication end carries modulation information reflected by a passive communication end, the signal is mixed with modulation information of light emitted by the active communication end, information modulated by the passive communication end, signal echoes, background light, an atmospheric light flickering signal and the like, so that the amplitude of the signal after photoelectric conversion is randomly and discretely changed, and the electric signal is in a level state of high, medium and low amplitudes, wherein the level state corresponds to three different logic states respectively. Therefore, the signal decision link becomes one of the most critical technologies of the receiving end, and its performance directly determines the Bit Error Rate (BER) and communication quality of the whole communication system. For conventional binary on-off keying (OOK) modulated signals, the most common decision method is the fixed threshold decision method. The fixed threshold judgment method is to preset a fixed voltage threshold, judge the signal higher than the voltage threshold as 1 and judge the signal lower than the voltage threshold as 0. However, in free space channels, laser transmission is affected by atmospheric turbulence, cloud cover, background noise (such as sunlight), and aiming errors caused by relative movement of the terminals, which can cause random and severe fluctuations in received light intensity (i.e., scintillation effects), such that the signal amplitude fluctuates substantially in a time scale of milliseconds or less. In this case, a fixed decision threshold cannot be changed with the time-varying characteristics of the signal, resulting in a steep rise in the decision error rate, and a so-called bit error rate plateau (BER floor) phenomenon is generated, i.e., the bit error rate cannot be reduced below a certain threshold regardless of the increase of the transmission power, which is unacceptable for a communication system with high reliability requirements. Particularly in full duplex retroreflective modulation communication scenarios, it is desirable to demodulate information in multiple states simultaneously, with the signal exhibiting a tri-state or even more level values. From this, the fixed threshold decision method is completely incapable of effectively demodulating the complex signal. In order to solve the technical difficulties that the traditional fixed threshold decision method is difficult to adjust the threshold according to the real-time channel state, thereby causing the increase of the erro