A free space optical communication real-time regulation system based on optical bump technology

Abstract

The application discloses a free space optical communication real-time regulation system based on light top technology, and belongs to the field of space optical communication. An AMCC transmitting module superimposes an AMCC signal on a service signal to form a mixed optical signal by controlling the bias voltage of a VOA; the mixed optical signal is transmitted to a free space channel through a space optical lens group; a beam splitter divides the received optical signal into communication side information and control side information; on the control side, the optical signal is received by an APD and converted into an electrical signal, which is sent into an AMCC receiving module after being sampled by an ADC, and the regulation information is fed back to a coherent receiver after being processed; the coherent receiver receives the regulation information to regulate the board card state in real time; the application is based on AMCC technology, utilizes the parallel processing capacity of a field programmable gate array (FPGA), and realizes efficient regulation of free space optical communication.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of space optical communication, and particularly relates to free space optical communication (FSO) technology, and specifically relates to a free space optical communication real-time regulation system based on optical topping technology. BACKGROUND

[0002] With the increasing demand for communication, free space optical communication (FSO) has become an important technology in modern communication networks due to its characteristics of no need for complex fiber infrastructure, high bandwidth and low delay. However, the optical signal transmitted in free space is affected by factors such as atmospheric turbulence, beam alignment error and environmental interference, resulting in many challenges in signal quality and transmission stability. Topped signal is widely used due to its fast collection and timely feedback characteristics. The present application aims to solve the problem that the communication system cannot be adjusted in real time when facing external environmental changes, and to improve the reliability and stability of the communication system. SUMMARY

[0003] Therefore, the present application provides a free space optical communication real-time regulation system based on optical topping technology, which aims to solve the problem of signal quality and transmission stability caused by factors such as atmospheric turbulence, beam alignment error and environmental interference in free space optical communication. The system is based on AMCC technology and uses the parallel processing capability of field programmable gate array (FPGA) to realize efficient regulation of free space optical communication.

[0004] In order to achieve the above purpose, the technical scheme adopted by the present application is:

[0005] A free space optical communication real-time regulation system based on optical topping technology, comprising a coherent transmitter, a coherent receiver, an AMCC transmission module and an AMCC receiving module of an auxiliary management control channel, an erbium-doped fiber amplifier, a high-speed high-sensitivity electrically controlled adjustable optical attenuator, a high-sensitivity avalanche photodiode, a space optical lens group, a light splitter and an analog-to-digital converter;

[0006] Transmission process: the coherent transmitter generates a QPSK signal, which is transmitted to the high-speed high-sensitivity electrically controlled adjustable optical attenuator after being processed by the erbium-doped fiber amplifier; the AMCC transmission module generates a topping signal in the form of amplitude modulation and controls the bias voltage of the high-speed high-sensitivity electrically controlled adjustable optical attenuator to superimpose the topping signal on the QPSK signal to form a mixed optical signal;

[0007] The mixed optical signal is transmitted in the free space channel through the space optical lens group;

[0008] The receiving process: the optical splitter separates the received optical signal into communication side and control side information; on the control side, the optical signal is received by a high-sensitivity avalanche photodiode and converted into an electrical signal, which enters the AMCC receiving module, and the AMCC receiving module feeds back the processed control information to the board card FPGA RX of the coherent receiver; on the communication side, the board card FPGA RX of the coherent receiver dynamically adjusts the demodulation parameters of the topping signal according to the control information, and demodulates the QPSK signal received by the coherent receiver through an adaptive filtering algorithm.

[0009] Further, the coherent transmitter generates an optical carrier through an external cavity laser, and the electrical signal generated by the board card FPGA TX is modulated by an IQ quadrature modulator to output a QPSK signal, which is amplified by an erbium-doped fiber amplifier and then sent to the topping signal superposition end.

[0010] Further, the topping signal of the AMCC transmitting module is superimposed with the service signal by changing the bias voltage of the high-speed high-sensitivity electrically controllable adjustable optical attenuator, and the modulation depth MD is defined as: ; wherein P0 represents the reference output power of the high-speed high-sensitivity electrically controllable adjustable optical attenuator, and P corresponds to the output power under different modulation depths.

[0011] Further, the auxiliary management control channel further comprises a calibration module, which automatically calibrates the linear working interval of the high-speed high-sensitivity electrically controllable adjustable optical attenuator when the system starts, to ensure that the correspondence between the MD value and the bias voltage meets the preset accuracy requirement.

[0012] The calibration module sends a stepped bias voltage to the high-speed high-sensitivity electrically controllable adjustable optical attenuator through the AMCC transmitting module, and collects the output optical power curve, and uses the least squares method to fit the linear interval, and finally stores the optimal bias range in the non-volatile memory.

[0013] Further, it further comprises a link monitoring module, and the generated mixed optical signal is transmitted through a spatial optical lens group, and the link monitoring module collects the quality of the mixed optical signal in the transmission process in real time, and generates optimization parameters based on the topping signal through the AMCC receiving module, which is used to optimize the DSP algorithm of the QPSK signal demodulation process.

[0014] Further, the QPSK signal is received by the integrated coherent receiver after passing through the optical splitter and is sent to the board card FPGA RX after beating with the local oscillator light, and the coherent receiver demodulates the received QPSK signal through the internal DSP algorithm to ensure the effective extraction of the QPSK signal.

[0015] Further, the top-adjusting signal is split by the optical splitter and reaches the high-sensitivity avalanche photodiode within the acceptable power range, is sampled by the analog-to-digital converter, and is processed by the DSP algorithm to obtain the demodulated top-adjusting signal and generate the optimization parameters based on the top-adjusting signal; the AMCC receiving module calculates the signal-to-noise ratio (SNR) of the top-adjusting signal in real time through the adaptive filtering algorithm, and dynamically adjusts the cutoff frequency of the low-pass filter according to the SNR value to ensure the effective extraction of the AMCC signal.

[0016] Further, the modulation depth of the top-adjusting signal is feedback adjusted and dynamically adjusted according to the real-time bit error rate (BER) of the QPSK signal, specifically including: when the BER of the QPSK exceeds the preset threshold, the MD value is reduced to reduce the power loss of the QPSK signal; when the BER is lower than the preset threshold, the MD value is gradually increased to enhance the transmission efficiency of the QPSK signal.

[0017] The beneficial effects produced by the above optimization technical solution are:

[0018] 1. Communication regulation system based on top adjustment: using the top adjustment technology based on the electrically controlled high-speed high-sensitivity electrically controllable variable optical attenuator (VOA), the problem of complex regulation and detection of the link in the free space optical communication process can be solved, and a reliable sending and receiving communication mechanism is provided to support stable signal transmission of control and communication mixed signals.

[0019] 2. High efficiency of data transmission: using the parallel processing capability of FPGA, the efficient transmission and real-time feedback of the AMCC signal are realized, and the response speed and accuracy of the system are improved.

[0020] 3. Low loss of control signal: by optimizing the modulation depth of the high-speed high-sensitivity electrically controllable variable optical attenuator, the power loss of the AMCC signal to the signal is reduced under the premise of ensuring stable transmission of the service signal, and the overall performance of the system is improved.

[0021] 4. High sensitivity of control signal: the transmission and reception of MHz-level control signals ensure stable reception with high sensitivity, and the purpose of stable regulation of the control side link can be achieved in the case of poor communication side effect.

[0022] 5. Based on the original transceiver system: the system realizes the transmission of multiple signals in the same channel without changing the original transceiver, reduces the complexity and cost of the system, and realizes the transmission of multiple signals in the same channel by superimposing the top-adjusting signal on the communication channel.

[0023] 6. Flexible adjustment of control signal: it can adapt to different communication scenes and environmental conditions, and flexibly control the superposition and transmission of the AMCC signal by adjusting the bias voltage and modulation depth of the high-speed high-sensitivity electrically controllable variable optical attenuator. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The system transmitting end structure diagram of the embodiment of the present application.

[0025] Figure 2 The system receiving end structure diagram of the embodiment of the present application. DETAILED DESCRIPTION

[0026] The present application provides a kind of free space optical communication real-time control system based on light topping technology, the specific implementation of the present application is described in detail below in conjunction with drawings and examples.The technical solution of the present application and its implementation mode can be understood by the person skilled in the art through the following description, but the protection scope of the present application is not limited to this embodiment.

[0027] System hardware composition and connection mode:

[0028] With reference to Figure 1 And Figure 2 The hardware composition of the present system mainly includes coherent transmitter, coherent receiver, AMCC transmitting module and AMCC receiving module of auxiliary management control channel, erbium-doped fiber amplifier (EDFA), high-speed high-sensitivity electrically controlled adjustable optical attenuator (VOA, optical attenuator in the figure), space optical lens group and optical splitter.Coherent transmitter is composed of external cavity laser (ECL), IQ quadrature modulator and board card FPGA TX;Coherent receiver is composed of local oscillator light (LO), integrated coherent receiver (ICR), analog-to-digital converter (ADC) and board card FPGA RX;AMCC receiving module is composed of high-sensitivity avalanche photodiode (APD), analog-to-digital converter (ADC) and DSP module.These components are connected through precise optical circuit and electric circuit to form a complete communication and control system.

[0029] Specific connection mode is as follows: external cavity laser (ECL) generates stable optical carrier and inputs to IQ quadrature modulator;Board card FPGA TX generates QPSK baseband signal, after pre-equalization, pre-coding and non-linear compensation algorithm processing, drives IQ modulator to modulate electrical signal to optical carrier, forms QPSK optical signal;After amplification by erbium-doped fiber amplifier, it is sent to high-speed high-sensitivity electrically controlled adjustable optical attenuator;AMCC transmitting module generates low-frequency topping signal, and the bias voltage of high-speed high-sensitivity electrically controlled adjustable optical attenuator is controlled to superimpose the topping signal on QPSK signal in amplitude modulation mode, to form hybrid optical signal;Hybrid signal is transmitted to free space channel through space optical lens group.

[0030] The receiving end divides the received mixed optical signal into two paths by a beam splitter: the communication side signal is received by the ICR, is converted into an electrical signal after beating with the local oscillator light, and is sent to the board card FPGA RX for coherent demodulation; the control side signal is received by a high-sensitivity avalanche photodiode, is sent to a DSP module for processing after being sampled by an ADC, generates control information, and is fed back to the board card FPGA RX, and the FPGA RX dynamically adjusts the demodulation parameters according to the feedback information, to realize real-time control.

[0031] Detailed description of the transmitting process:

[0032] The transmitting process starts from the board card FPGA TX generating a 10 GHz rate QPSK baseband signal. The signal is first processed by the DSP unit, including pre-equalization to compensate for channel distortion, precoding to improve spectral efficiency, and non-linear compensation to suppress non-linear effects in the transmission process. The processed electrical signal drives the IQ modulator to modulate the signal onto the optical carrier generated by the external cavity laser (ECL) to form a QPSK optical signal. The optical signal is amplified to an appropriate transmission power level by an erbium-doped fiber amplifier (EDFA), and then sent to a high-speed high-sensitivity electrically controlled variable optical attenuator (VOA).

[0033] The AMCC transmitting module generates a low-frequency tipping signal with a frequency of 1 MHz, which is superimposed on the QPSK signal in an amplitude modulation manner by changing the bias voltage of the high-speed high-sensitivity electrically controlled variable optical attenuator (VOA). The modulation depth (MD) is dynamically adjusted according to the system state to ensure the optimal power distribution between the service signal and the tipping signal. The mixed optical signal is finally collimated and transmitted to the free space channel through a spatial optical lens group.

[0034] Detailed description of the receiving process:

[0035] At the receiving end, the beam splitter divides the received mixed optical signal into two paths in a 1:99 ratio. The communication side optical signal is sent to the integrated coherent receiver (ICR), beats with the local oscillator light, and is converted into an electrical signal, which is received by the board card FPGA RX. The board card FPGA RX internally integrates advanced DSP algorithms, including adaptive equalization, carrier phase recovery, and timing synchronization modules, to perform coherent demodulation on the QPSK signal, ensuring high-quality recovery of the signal.

[0036] The control side light signal is received by a high-sensitivity avalanche photodiode (APD), which can effectively detect weak light signals and convert them into electrical signals due to its high responsivity and internal gain. The electrical signal is converted into a digital signal after being sampled by an analog-to-digital converter (ADC) and sent to the AMCC receiving module. The AMCC receiving module uses an adaptive filtering algorithm to calculate the signal-to-noise ratio (SNR) of the modulation signal in real time, and dynamically adjusts the cutoff frequency of the low-pass filter according to the SNR value to optimize the signal extraction effect. The extracted control information (such as link quality, bit error rate, etc.) is fed back to the board card FPGA RX for real-time adjustment of the demodulation parameters.

[0037] System control mechanism and optimization strategy:

[0038] The core control mechanism of the system is based on the real-time feedback of the AMCC signal. The board card FPGA RX dynamically adjusts the demodulation parameters of the QPSK signal, including equalizer coefficients, carrier recovery loop bandwidth, and decision threshold, according to the received AMCC information, to adapt to channel changes. In addition, the system also integrates a link monitoring module to collect signal quality parameters such as frequency offset, phase noise, and optical power fluctuations in real time, and uses these data to optimize the performance of the DSP algorithm.

[0039] The modulation signal of the AMCC transmitting module is superimposed with the service signal by changing the bias voltage of the high-speed high-sensitivity electrically controlled adjustable optical attenuator, and the modulation depth MD is defined as: ; where P0 represents the reference output power of the high-speed high-sensitivity electrically controlled adjustable optical attenuator, and P corresponds to the output power under different modulation depths. The modulation depth (MD) can be adjusted according to the real-time bit error rate (BER) of the QPSK signal. When the BER exceeds the preset threshold, the system automatically reduces the MD value to reduce the power occupation of the modulation signal on the service signal; when the BER is lower than the threshold, the MD value is gradually increased to enhance the transmission efficiency of the AMCC signal. This dynamic adjustment mechanism ensures the stable operation of the system in complex environments.

[0040] Calibration and initialization process:

[0041] The calibration process of the VOA linear working interval is automatically executed when the system starts. The calibration module sends a series of stepwise bias voltages to the VOA through the AMCC transmitting module, while collecting the output optical power curve of the VOA. The collected data is fitted using the least squares method to determine the linear working interval of the VOA, and the optimal bias voltage range is stored in the non-volatile memory. This calibration process ensures that the correspondence between the modulation depth and the bias voltage meets the system accuracy requirements, providing a reliable foundation for subsequent real-time control.

[0042] System advantages and application scenario analysis

[0043] The system has the advantages of high integration, high real-time performance and high reliability. By using existing coherent optical communication equipment and introducing optical sideband technology, the control signal and the service signal are co-transmitted without significantly increasing the hardware complexity. The parallel processing capability of FPGA ensures the feedback speed of milliseconds, so that the system can quickly respond to channel changes. The introduction of AMCC signal makes the system have strong link monitoring and dynamic adjustment capability, which is suitable for various harsh environments such as atmospheric turbulence and alignment error. It can be widely used in space laser communication, unmanned aerial vehicle optical link, ground free-space optical communication relay and other optical communication scenes with high real-time performance and reliability requirements, and provides an effective real-time regulation solution for free-space optical communication.

[0044] The above only describes the preferred embodiments of the present application, and is not used to limit the protection scope of the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A real-time control system for free-space optical communication based on optical top-tuning technology, characterized in that, It includes a coherent transmitter, a coherent receiver, an AMCC transmitter module and an AMCC receiver module with an auxiliary management and control channel, an erbium-doped fiber amplifier, a high-speed, high-sensitivity electrically controlled tunable optical attenuator, a high-sensitivity avalanche photodiode, a spatial light lens head assembly, a beam splitter, and an analog-to-digital converter. Transmission process: The coherent transmitter generates a QPSK signal, which is processed by an erbium-doped fiber amplifier and then transmitted to a high-speed, high-sensitivity electrically controlled adjustable optical attenuator; the AMCC transmitter module generates a modulation signal in the form of amplitude modulation and controls the bias voltage of the high-speed, high-sensitivity electrically controlled adjustable optical attenuator to superimpose the modulation signal onto the QPSK signal to form a hybrid optical signal. The hybrid optical signal is transmitted in a free-space channel through a spatial optical lens group; Reception process: The optical splitter separates the received optical signal into communication-side and control-side information. On the control side, the optical signal is received by a high-sensitivity avalanche photodiode and converted into an electrical signal. The electrical signal enters the AMCC receiving module, which processes the modulation information and feeds it back to the FPGA RX board of the coherent receiver. On the communication side, the FPGA RX board of the coherent receiver dynamically adjusts the demodulation parameters of the QPSK signal according to the modulation information and demodulates the QPSK signal received by the coherent receiver through an adaptive filtering algorithm. The modulation signal of the AMCC transmitter module is superimposed on the service signal by changing the bias voltage of the high-speed, high-sensitivity, electrically controlled adjustable optical attenuator. The modulation depth MD is defined as: Where P0 represents the reference output power of the high-speed, high-sensitivity electronically controlled tunable optical attenuator, and P corresponds to the output power at different modulation depths. The auxiliary management and control channel also includes a calibration module. When the system starts up, the calibration module automatically calibrates the linear operating range of the high-speed, high-sensitivity electronically controlled adjustable optical attenuator to ensure that the correspondence between the MD value and the bias voltage meets the preset accuracy requirements. The calibration module sends a stepped bias voltage to the high-speed, high-sensitivity electrically controlled adjustable optical attenuator through the AMCC transmitter module, and acquires its output optical power curve. It then uses the least squares method to fit the linear interval and finally stores the optimal bias range in non-volatile memory.

2. The free-space optical communication real-time control system based on optical top-tuning technology according to claim 1, characterized in that, The coherent transmitter generates an optical carrier through an external cavity laser. The electrical signal generated by the FPGA TX on the board is modulated by an IQ quadrature modulator and output as a QPSK signal. After being amplified by an erbium-doped fiber amplifier, it is sent to the modulation signal superposition terminal.

3. The free-space optical communication real-time control system based on optical top-tuning technology according to claim 1, characterized in that, It also includes a link monitoring module. The generated hybrid optical signal is transmitted through a spatial optical lens group. The link monitoring module collects the quality of the hybrid optical signal in real time during the transmission process and generates optimized parameters based on the modulation signal through the AMCC receiving module, which are used to optimize the DSP algorithm for the QPSK signal demodulation process.

4. The free-space optical communication real-time control system based on optical top-tuning technology according to claim 1, characterized in that, After passing through the beam splitter, the QPSK signal is received by the integrated coherent receiver and beats the local oscillator light before being sent to the FPGARX board for reception. The coherent receiver demodulates the received QPSK signal using an internal DSP algorithm to ensure effective extraction of the QPSK signal.

5. A real-time control system for free-space optical communication based on optical top-tuning technology according to claim 1, characterized in that, The modulated signal is split by a beam splitter to reach the acceptable power range of the high-sensitivity avalanche photodiode. After sampling by an analog-to-digital converter, it is processed by a DSP algorithm to obtain the demodulated modulated signal and generate optimized parameters based on the modulated signal. The AMCC receiving module calculates the signal-to-noise ratio (SNR) of the modulated signal in real time through an adaptive filtering algorithm and dynamically adjusts the cutoff frequency of the low-pass filter of the high-sensitivity avalanche photodiode according to the SNR value to ensure effective extraction of the AMCC signal.

6. A real-time control system for free-space optical communication based on optical top-tuning technology according to claim 3, characterized in that, The modulation depth of the top-modulated signal is adjusted by feedback, and dynamically adjusted according to the real-time bit error rate of the QPSK signal. Specifically, when the BER of the QPSK exceeds a preset threshold, the MD value is reduced to reduce the power loss of the QPSK signal; when the BER of the QPSK is lower than a preset threshold, the MD value is gradually increased to enhance the transmission efficiency of the AMCC signal.

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