High-security multi-constellation shaping modulation with asymmetric encryption
Lei Jiang, Bo Liu, Jianxin Ren, Xiangyu Wu, Rahat Ullah, Yaya Mao, Shuaidong Chen, Yilan Ma, Lilong Zhao, and Feng Tian
This Letter proposes a high-security modulation scheme for optical transmission systems. By using multi-constellation shaping and asymmetric encryption, the information security can be enhanced and quantum computer cracking can be effectively resisted. Three-dimensional (3D) carrier-less amplitude phase modulation is utilized to superposition and transmit 3D signals. Experimental verification is conducted using a seven-core weakly coupled fiber platform. The results demonstrate that the proposed scheme can effectively protect the system from any illegal attacker.This Letter proposes a high-security modulation scheme for optical transmission systems. By using multi-constellation shaping and asymmetric encryption, the information security can be enhanced and quantum computer cracking can be effectively resisted. Three-dimensional (3D) carrier-less amplitude phase modulation is utilized to superposition and transmit 3D signals. Experimental verification is conducted using a seven-core weakly coupled fiber platform. The results demonstrate that the proposed scheme can effectively protect the system from any illegal attacker.
- Apr. 26, 2024
- Chinese Optics Letters
- Vol. 22, Issue 4, 040602 (2024)
- DOI：10.3788/COL202422.040602
Neural network equalization based on delta-sigma modulation
Bo Liu, Jianxin Ren, Xiangyu Wu, Shuaidong Chen, Yaya Mao, and Li Zhao
We propose a neural network equalization delta-sigma modulation (DSM) technique. After performing DSM on the multi-order quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) signal at the transmitting end, neural network equalizer technology is used in the digital signal processing at receiving end. Applying this technology to a 4.6 km W-band millimeter wave system, it is possible to achieve a 1 Gbaud 8192-QAM OFDM signal transmission. The data rate reached 23.4 Gbit/s with the bit error rate at 3.8 × 10-2, lower than soft-decision forward-error correction threshold (4 × 10-2).We propose a neural network equalization delta-sigma modulation (DSM) technique. After performing DSM on the multi-order quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) signal at the transmitting end, neural network equalizer technology is used in the digital signal processing at receiving end. Applying this technology to a 4.6 km W-band millimeter wave system, it is possible to achieve a 1 Gbaud 8192-QAM OFDM signal transmission. The data rate reached 23.4 Gbit/s with the bit error rate at 3.8 × 10-2, lower than soft-decision forward-error correction threshold (4 × 10-2).
- Apr. 26, 2024
- Chinese Optics Letters
- Vol. 22, Issue 4, 040601 (2024)
- DOI：10.3788/COL202422.040601
Low-cost, large-coverage, and high-flexibility coherent PON for next-generation access networks: advances, challenges, and prospects [Invited] | On the Cover
Sizhe Xing, Junwen Zhang, Wangwei Shen, An Yan, Guoqiang Li, Aolong Sun, Ji Zhou, Dong Guo, Jianyang Shi, Ziwei Li, Chao Shen, and Nan Chi
Increasing bandwidth requirements have posed significant challenges for traditional access networks. It is difficult for intensity modulation/direct detection to meet the power budget and flexibility requirements of the next-generation passive optical network (PON) at 100G and beyond considering the new requirements. This is driving researchers to develop novel optical access technologies. Low-cost, wide-coverage, and high-flexibility coherent PON is emerging as a strong contender in the competition. In this article, we will review technologies that reduce the complexity of coherent PON (CPON), enabling it to meet the commercial requirements. Also, advanced algorithms and architectures that can enhance system coverage and flexibility are also discussed.Increasing bandwidth requirements have posed significant challenges for traditional access networks. It is difficult for intensity modulation/direct detection to meet the power budget and flexibility requirements of the next-generation passive optical network (PON) at 100G and beyond considering the new requirements. This is driving researchers to develop novel optical access technologies. Low-cost, wide-coverage, and high-flexibility coherent PON is emerging as a strong contender in the competition. In this article, we will review technologies that reduce the complexity of coherent PON (CPON), enabling it to meet the commercial requirements. Also, advanced algorithms and architectures that can enhance system coverage and flexibility are also discussed.
- Apr. 18, 2024
- Chinese Optics Letters
- Vol. 22, Issue 4, 040604 (2024)
- DOI：10.3788/COL202422.040604
Performance Analysis of OOK and BPSK Compatible Laser Communication
Funan Zhu, Jiawei Li, Shaowen Lu, and Weibiao Chen
To adapt to the networking technology of space laser communication, the multi-system multiplexed communication mode was developed. In the transmitter, an intensity modulator is used to realize on-off keying (OOK) and binary phase shift keying (BPSK) modulation compatibility; while in the receiver, demodulation of these two modulation signals is realized via intradyne detection. In practical engineering applications, shot noise and thermal noise of electronic devices in laser communication system will inevitably affect the communication performance. Accordingly, the influences of bias point error of intensity modulator and optical filter bandwidth on the signal-to-noise ratio of incoherent OOK and coherent BPSK communication are further analyzed herein. Simulation results show that the optical filter bandwidth significantly influences the incoherent OOK communication performance: the incoherent OOK SNR overhead of 1 nm filter bandwidth is approximately 1.26 when the received optical power is -46 dBm; the coherent BPSK SNR overhead of 20 nm filter bandwidth is less than 0.02 when the received optical power is below -50 dBm. If the codeless communication sensitivity of incoherent OOK is required to meet -46 dBm@10-6 at the rate of 1.25 Gbit/s, the optical filter bandwidth should not be greater than 0.8 nm, the bias error of the intensity modulator should be controlled within 1% of the half-wave voltage. Under the condition of common-mode noise elimination and optimized optical filter bandwidth, the codeless sensitivity of BPSK communication at 1.25 Gbit/s rate is satisfactory to -55 dBm@10-6.To adapt to the networking technology of space laser communication, the multi-system multiplexed communication mode was developed. In the transmitter, an intensity modulator is used to realize on-off keying (OOK) and binary phase shift keying (BPSK) modulation compatibility; while in the receiver, demodulation of these two modulation signals is realized via intradyne detection. In practical engineering applications, shot noise and thermal noise of electronic devices in laser communication system will inevitably affect the communication performance. Accordingly, the influences of bias point error of intensity modulator and optical filter bandwidth on the signal-to-noise ratio of incoherent OOK and coherent BPSK communication are further analyzed herein. Simulation results show that the optical filter bandwidth significantly influences the incoherent OOK communication performance: the incoherent OOK SNR overhead of 1 nm filter bandwidth is approximately 1.26 when the received optical power is -46 dBm; the coherent BPSK SNR overhead of 20 nm filter bandwidth is less than 0.02 when the received optical power is below -50 dBm. If the codeless communication sensitivity of incoherent OOK is required to meet -46 dBm@10-6 at the rate of 1.25 Gbit/s, the optical filter bandwidth should not be greater than 0.8 nm, the bias error of the intensity modulator should be controlled within 1% of the half-wave voltage. Under the condition of common-mode noise elimination and optimized optical filter bandwidth, the codeless sensitivity of BPSK communication at 1.25 Gbit/s rate is satisfactory to -55 dBm@10-6.
- Apr. 10, 2024
- Laser & Optoelectronics Progress
- Vol. 61, Issue 7, 0706020 (2024)
- DOI：10.3788/LOP232184
Research Progress and Future Directions in Deep Space Optical Communication (Invited)
Chao Liu, Xueying Li, Kaihe Zhang, Bin Lan, Tianjun Dai, and Hao Xian
With the deepening exploration of space by humans, traditional radio frequency (RF) communication increasingly fails to meet the demands of high-speed deep space communication. Various spacefaring nations have undertaken research on deep space optical communication technology. Optical communication is a crucial means of achieving space communication. Compared to traditional RF communication, optical communication offers advantages such as high communication speed, small terminal payload, strong anti-interference capabilities and so on, making it more suitable for ultra-long-distance deep space communication. Currently, the United States leads in research and has successfully conducted two deep space optical communication demonstrations. This paper provides a comprehensive review of existing research plans and demonstration results in deep space optical communication. It analyzes the key technologies for implementing deep space optical communication, reflects on the developmental history, and contemplates the future prospects of deep space optical communication.With the deepening exploration of space by humans, traditional radio frequency (RF) communication increasingly fails to meet the demands of high-speed deep space communication. Various spacefaring nations have undertaken research on deep space optical communication technology. Optical communication is a crucial means of achieving space communication. Compared to traditional RF communication, optical communication offers advantages such as high communication speed, small terminal payload, strong anti-interference capabilities and so on, making it more suitable for ultra-long-distance deep space communication. Currently, the United States leads in research and has successfully conducted two deep space optical communication demonstrations. This paper provides a comprehensive review of existing research plans and demonstration results in deep space optical communication. It analyzes the key technologies for implementing deep space optical communication, reflects on the developmental history, and contemplates the future prospects of deep space optical communication.
- Apr. 10, 2024
- Laser & Optoelectronics Progress
- Vol. 61, Issue 7, 0706007 (2024)
- DOI：10.3788/LOP240902
Dynamic Routing and Spectrum Allocation Algorithms in Elastic Optical Networks for Satellite Internet (Invited)
Hai Li, Yongjun Li, Yuanhao Liu, Xing Li, Yu Li, and Shanghong Zhao
Satellite Elastic Optical Network (SEON) is an important development direction of satellite Internet with the advantages of large capacity, strong anti-interference ability and flexible resource management and control. The routing and spectrum allocation (RSA) problem is a critical issue in SEON. To solve the RSA problem in SEON, a dynamic routing and spectrum allocation algorithm based on the path state-aware (PIV-SSA) is proposed. The PIV-SSA consists of a segmented spectrum allocation (SSA) algorithm and a path influence value routing selection (PIV) algorithm. In the SSA, the location of the spectrum resources allocated to the services are determined by the transmission rate it requires. In the PIV, the optimal transmission path is selected by comprehensively considering factors such as spectrum resource consumption, link spectrum status, and path survival time based on the pre-allocation results of the SSA algorithm. The results of the simulation experiments show that, compared to the classical KSP-FF algorithm, the PIV-SSA algorithm reduces the network blocking rate by an average of 4.60% and achieves an average improvement of 4.78% in network spectrum utilization under different load intensities.Satellite Elastic Optical Network (SEON) is an important development direction of satellite Internet with the advantages of large capacity, strong anti-interference ability and flexible resource management and control. The routing and spectrum allocation (RSA) problem is a critical issue in SEON. To solve the RSA problem in SEON, a dynamic routing and spectrum allocation algorithm based on the path state-aware (PIV-SSA) is proposed. The PIV-SSA consists of a segmented spectrum allocation (SSA) algorithm and a path influence value routing selection (PIV) algorithm. In the SSA, the location of the spectrum resources allocated to the services are determined by the transmission rate it requires. In the PIV, the optimal transmission path is selected by comprehensively considering factors such as spectrum resource consumption, link spectrum status, and path survival time based on the pre-allocation results of the SSA algorithm. The results of the simulation experiments show that, compared to the classical KSP-FF algorithm, the PIV-SSA algorithm reduces the network blocking rate by an average of 4.60% and achieves an average improvement of 4.78% in network spectrum utilization under different load intensities.
- Apr. 10, 2024
- Laser & Optoelectronics Progress
- Vol. 61, Issue 7, 0706006 (2024)
- DOI：10.3788/LOP240526
Integration of Laser Communication and Aiming Based on High Sensitivity Beam Position Signal Extraction (Invited)
Xinyu Chen, Shaowen Lu, Funan Zhu, Yongbo Fan, Qiong Hu, Haowei Xia, Jianfeng Sun, Ren Zhu, Xia Hou, and Weibiao Chen
A space optical communication system with intensity modulation direct detection based on four quadrant detector tracking and communication multiplexing has been reported, which uses the dual optical wedge driven by ultrasonic motor as the beam deflection execution unit to form a closed-loop system for beam position tracking. The rotation period of the driving motor is 15 ms, and the position resolution is 0.83 μrad. Through theoretical analysis and experimental verification, the position closed-loop tracking -3 dB bandwidth of this system is about 4 Hz. When the position detection error is less than 10%, that is, the beam detection accuracy is less than 12 μrad, and the corresponding detection sensitivity is -45.2 dBm. At a communication rate of 10 Mbit/s and without signal encoding, the corresponding communication sensitivity is -44 dBm when the bit error rate is 1×10-3. It has been verified that it is feasible to use the four-quadrant detector as a tracking and communication multiplexing detector, which can be applied to small and lightweight interstellar laser communication terminals.A space optical communication system with intensity modulation direct detection based on four quadrant detector tracking and communication multiplexing has been reported, which uses the dual optical wedge driven by ultrasonic motor as the beam deflection execution unit to form a closed-loop system for beam position tracking. The rotation period of the driving motor is 15 ms, and the position resolution is 0.83 μrad. Through theoretical analysis and experimental verification, the position closed-loop tracking -3 dB bandwidth of this system is about 4 Hz. When the position detection error is less than 10%, that is, the beam detection accuracy is less than 12 μrad, and the corresponding detection sensitivity is -45.2 dBm. At a communication rate of 10 Mbit/s and without signal encoding, the corresponding communication sensitivity is -44 dBm when the bit error rate is 1×10-3. It has been verified that it is feasible to use the four-quadrant detector as a tracking and communication multiplexing detector, which can be applied to small and lightweight interstellar laser communication terminals.
- Apr. 10, 2024
- Laser & Optoelectronics Progress
- Vol. 61, Issue 7, 0706016 (2024)
- DOI：10.3788/LOP232772
Integrated Technology of Laser Spread Spectrum Communication and Ranging for Deep Space (Invited)
Chaoyang Li, Jianfeng Sun, Zhiyong Lu, Yu Zhou, Longkun Zhang, Yuxin Jiang, Lingling Xu, Hanrui Pan, Honghui Jia, Haoming Yuan, Weibiao Chen, and Hui He
In deep space exploration, microwave-based communication and ranging payloads face problems such as high link loss and tight spectrum resources. Compared with microwave, laser beam has a small divergence angle and more concentrated energy, which can reach a longer transmission distance, and the laser-based communication and ranging payloads have the advantages of small size and light weight. In this paper, an integrated deep space exploration system based on laser coherent heterodyne spread spectrum communication and ranging is constructed, an interpolation resampling method based on a curve model is proposed, and theoretical simulation and experimental verification of the curve model are carried out. The model is constructed from a priori information of the system and is a linear function of the pseudo-random code phase difference. The experimental results show that for static targets, the ranging deviation is no more than 0.55 mm and the ranging precision does not exceed 0.42 mm, and for dynamic targets, the ranging deviation is no more than 0.59 mm. Communication with zero bit rate is also realized in ranging for static and dynamic target. In addition, the integrated design of spread-spectrum communication and ranging is applied to deep space navigation and deep space time-frequency synchronization, which can improve the real-time performance.In deep space exploration, microwave-based communication and ranging payloads face problems such as high link loss and tight spectrum resources. Compared with microwave, laser beam has a small divergence angle and more concentrated energy, which can reach a longer transmission distance, and the laser-based communication and ranging payloads have the advantages of small size and light weight. In this paper, an integrated deep space exploration system based on laser coherent heterodyne spread spectrum communication and ranging is constructed, an interpolation resampling method based on a curve model is proposed, and theoretical simulation and experimental verification of the curve model are carried out. The model is constructed from a priori information of the system and is a linear function of the pseudo-random code phase difference. The experimental results show that for static targets, the ranging deviation is no more than 0.55 mm and the ranging precision does not exceed 0.42 mm, and for dynamic targets, the ranging deviation is no more than 0.59 mm. Communication with zero bit rate is also realized in ranging for static and dynamic target. In addition, the integrated design of spread-spectrum communication and ranging is applied to deep space navigation and deep space time-frequency synchronization, which can improve the real-time performance.
- Apr. 10, 2024
- Laser & Optoelectronics Progress
- Vol. 61, Issue 7, 0706013 (2024)
- DOI：10.3788/LOP240428
Research Progress on Liquid Crystal Optical Phased Array Technology for Laser Communication (Invited)
Xiaoxian He, Siyu Zhou, Jixiang Zhao, and Xiangru Wang
Optical phased array (OPA), a nonmechanical beam steering technology, greatly improves the efficiency and stability of optical systems. It offers various advantages, including lightweight construction, compact size, fast beamforming, and low power consumption, rendering it extensively applicable across various fields. This paper provides an overview of the research advancements in liquid crystal-based OPAs employed for beam steering in laser communication. Furthermore, we outline the current challenges and prospects of liquid crystal OPAs in laser communication.Optical phased array (OPA), a nonmechanical beam steering technology, greatly improves the efficiency and stability of optical systems. It offers various advantages, including lightweight construction, compact size, fast beamforming, and low power consumption, rendering it extensively applicable across various fields. This paper provides an overview of the research advancements in liquid crystal-based OPAs employed for beam steering in laser communication. Furthermore, we outline the current challenges and prospects of liquid crystal OPAs in laser communication.
- Apr. 10, 2024
- Laser & Optoelectronics Progress
- Vol. 61, Issue 7, 0706004 (2024)
- DOI：10.3788/LOP240715
Rough Tracking Method for Satellite Laser Communication Based on YOLOv5s(Invited)
Peng Yin, Xiaolong Ni, Chunyi Chen, and Xin Yu
To solve the problem of traditional beacon laser spot detection algorithms being susceptible to complex background interference during the initial capture stage of satellite laser communication. YOLOv5s neural network is used to optimize and improve the initial pointing scene of satellite platforms. Selecting the original loss function with the smoothed intersection over union (SIoU) loss function and replacing the original upsampling structure with a lightweight content aware feature recombination (CARAFE) upsampling structure, adding convolutional block attention module (CBAM) attention mechanism to C3 layer, using SimSPPF to replace the original structure, and adding Coordconv structure that is conducive to perceiving position information. The improved neural network has better accuracy than traditional coarse tracking beacon spot detection algorithms, and can accurately detect the position of the spot in complex backgrounds. It is suitable for beacon spot detection in the initial capture stage and coarse tracking stage. The optimized YOLOv5s neural network achieves a precision rate of 99.7%, a recall rate of 99.3%, and exceeds the average accuracy (mAP) @0.5 by 99.7% and mAP@0.5∶0.95 by 74%.To solve the problem of traditional beacon laser spot detection algorithms being susceptible to complex background interference during the initial capture stage of satellite laser communication. YOLOv5s neural network is used to optimize and improve the initial pointing scene of satellite platforms. Selecting the original loss function with the smoothed intersection over union (SIoU) loss function and replacing the original upsampling structure with a lightweight content aware feature recombination (CARAFE) upsampling structure, adding convolutional block attention module (CBAM) attention mechanism to C3 layer, using SimSPPF to replace the original structure, and adding Coordconv structure that is conducive to perceiving position information. The improved neural network has better accuracy than traditional coarse tracking beacon spot detection algorithms, and can accurately detect the position of the spot in complex backgrounds. It is suitable for beacon spot detection in the initial capture stage and coarse tracking stage. The optimized YOLOv5s neural network achieves a precision rate of 99.7%, a recall rate of 99.3%, and exceeds the average accuracy (mAP) @0.5 by 99.7% and mAP@0.5∶0.95 by 74%.
- Apr. 10, 2024
- Laser & Optoelectronics Progress
- Vol. 61, Issue 7, 0706012 (2024)
- DOI：10.3788/LOP240883
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