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Fiber Optics and Optical Communications|738 Article(s)
Photonics-Aided Quadruple Frequency W-Band Linear Frequency Modulated Signal Sensing and Ranging
Longwei Pan, Yanyi Wang, Yuxuan Tan, Yuangang Wang, Kaihui Wang, and Wen Zhou
A new system based on optical external modulator frequency multiplication is proposed to generate W-band linear frequency modulated (LFM) signals for high-resolution ranging. The LFM signals from the arbitrary waveform generator (AWG) are modulated to the sideband of the optical carrier through the optical modulator. The photoelectric conversion is completed in the photodetector (PD) to generate quadruple frequency W-band LFM signals, whose center frequency and bandwidth are four times the original LFM signal. This broadband LFM signal is emitted to free space for target detection. For distance measurements, the two targets are separated by 50 cm, and the measured value is 48.8 cm with an error of 1.2 cm. The distance between the two objects is set to 40 cm to demonstrate the reliability of the experiment. The measured value is 38.9 cm, and the error is 1.1 cm. The system overcomes the “electronic bottleneck” that is difficult to directly generate high-frequency signals in the electrical domain and achieves high-resolution ranging via photonics-aided generation of the broadband LFM signal. Thus, the proposed method provides a solution for future ultrahigh-resolution LFM continuous-wave radar systems. A new system based on optical external modulator frequency multiplication is proposed to generate W-band linear frequency modulated (LFM) signals for high-resolution ranging. The LFM signals from the arbitrary waveform generator (AWG) are modulated to the sideband of the optical carrier through the optical modulator. The photoelectric conversion is completed in the photodetector (PD) to generate quadruple frequency W-band LFM signals, whose center frequency and bandwidth are four times the original LFM signal. This broadband LFM signal is emitted to free space for target detection. For distance measurements, the two targets are separated by 50 cm, and the measured value is 48.8 cm with an error of 1.2 cm. The distance between the two objects is set to 40 cm to demonstrate the reliability of the experiment. The measured value is 38.9 cm, and the error is 1.1 cm. The system overcomes the “electronic bottleneck” that is difficult to directly generate high-frequency signals in the electrical domain and achieves high-resolution ranging via photonics-aided generation of the broadband LFM signal. Thus, the proposed method provides a solution for future ultrahigh-resolution LFM continuous-wave radar systems.
Laser & Optoelectronics Progress
- Publication Date: May. 10, 2024
- Vol. 61, Issue 9, 0906006 (2024)
Design of Ground Receiver System For 500 mm Aperture Satellite-Ground Laser Communication
Cong Li, Xiaolong Ni, Xin Yu, Jun Liu, Suping Bai, and Lixia Shi
In order to enhance the sensitivity and resolution of the ground receiver for satellite-based laser communication, as well as simplify the acquisition process for beacon light, a 500 mm aperture ground receiver system is developed. This system is designed based on the link and design scheme of satellite-based laser communication, incorporating adaptive optics (AO) technology. It consists of four units: Cassegrain antenna with common aperture spectral detection, precision tracking tilt mirror, ultra-precision tracking AO, and AO wavefront detection. The antenna objective utilizes a coaxial Cassegrain structure combined with a refractor group to form a Kepler telescopic structure that considers volume and pupil distance requirements. To address optical axis correction issues causing pupil plane drift, a 4f system is implemented between the precise tracking tilt mirror and AO tilt mirror. Additionally, a double telecentric system is employed between the wavefront detector and deformable mirror to establish conjugate relationship and minimize axial error in wavefront detection. Optical passive methods are utilized in designing these four units to improve temperature adaptability of the system. Experimental results demonstrate that each element's wave aberration falls within 1/10λ (λ=632.8 nm) range at temperatures ranging from 10 ℃ to 30 ℃, meeting design specifications while offering valuable references for engineering applications. In order to enhance the sensitivity and resolution of the ground receiver for satellite-based laser communication, as well as simplify the acquisition process for beacon light, a 500 mm aperture ground receiver system is developed. This system is designed based on the link and design scheme of satellite-based laser communication, incorporating adaptive optics (AO) technology. It consists of four units: Cassegrain antenna with common aperture spectral detection, precision tracking tilt mirror, ultra-precision tracking AO, and AO wavefront detection. The antenna objective utilizes a coaxial Cassegrain structure combined with a refractor group to form a Kepler telescopic structure that considers volume and pupil distance requirements. To address optical axis correction issues causing pupil plane drift, a 4f system is implemented between the precise tracking tilt mirror and AO tilt mirror. Additionally, a double telecentric system is employed between the wavefront detector and deformable mirror to establish conjugate relationship and minimize axial error in wavefront detection. Optical passive methods are utilized in designing these four units to improve temperature adaptability of the system. Experimental results demonstrate that each element's wave aberration falls within 1/10λ (λ=632.8 nm) range at temperatures ranging from 10 ℃ to 30 ℃, meeting design specifications while offering valuable references for engineering applications.
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2024
- Vol. 61, Issue 7, 0706021 (2024)
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.
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2024
- Vol. 61, Issue 7, 0706020 (2024)
Laser Ranging Data Assessment and Improvement of Changchun Station Using Precise Ephemerides
Hongyu Long, Xue Dong, Zhipeng Liang, Xingwei Han, Bowen Guan, and He Dong
In order to improve the satellite laser ranging data accuracy and stability of Changchun Station, analysis was performed with a data assessment system using precise satellite ephemerides. The assessment system was established from physical mechanism and widely recognized evaluation standard of satellite laser ranging, using precise orbit ephemerides as input. With the help of above assessment system, a new method known as the leading edge half maximum (LEHM) algorithm is used to improve the data pre-processing method and reduce the impact of satellite signature effect on data accuracy and stability. Analysis showed that the output of the data assessment system is consistent with those of International Laser Ranging Service (ILRS) analysis centers. After data pre-processing with the LEHM algorithm, normal point accuracy was improved from 4.9 mm to 3.9 mm, short-term stability was improved from 19.8 mm to 18.1 mm, long-term stability was improved from 6.2 mm to 5.4 mm and range accuracy was improved from 79.6 mm to 68.2 mm. The LEHM algorithm can effectively improve the data accuracy and stability, which points out the way to further improve the accuracy and stability of Changchun laser ranging data. In order to improve the satellite laser ranging data accuracy and stability of Changchun Station, analysis was performed with a data assessment system using precise satellite ephemerides. The assessment system was established from physical mechanism and widely recognized evaluation standard of satellite laser ranging, using precise orbit ephemerides as input. With the help of above assessment system, a new method known as the leading edge half maximum (LEHM) algorithm is used to improve the data pre-processing method and reduce the impact of satellite signature effect on data accuracy and stability. Analysis showed that the output of the data assessment system is consistent with those of International Laser Ranging Service (ILRS) analysis centers. After data pre-processing with the LEHM algorithm, normal point accuracy was improved from 4.9 mm to 3.9 mm, short-term stability was improved from 19.8 mm to 18.1 mm, long-term stability was improved from 6.2 mm to 5.4 mm and range accuracy was improved from 79.6 mm to 68.2 mm. The LEHM algorithm can effectively improve the data accuracy and stability, which points out the way to further improve the accuracy and stability of Changchun laser ranging data.
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2024
- Vol. 61, Issue 7, 0706019 (2024)
Pointing Angle Calculation and Aiming Accuracy Analysis of a Lunar Laser Ranging Retro-Reflector
Wuqi Pan, Zhien Cheng, Zhongping Zhang, and Xinhao Liao
Lunar laser ranging (LLR) has the highest precision in measuring the earth-moon distance. The lunar laser ranging retro-reflector (LRRR) is an essential piece of equipment for realizing lunar laser ranging. China has plans to deploy a manually emplaced new generation LRRR. For the LRRR to work effectively, the azimuth and altitude angle of the LRRR must be adjusted such that the LRRR is aligned with the mean Earth direction. We established a method for calculating the adjustment angle of the LRRR and analyzed the misalignment caused by the biases of emplacement time and emplacement site. Results show that the aiming of error of the LRRR can be estimated at approximately 2.7°, and the maximum value is less than 5.0°, which satisfies the requirements for an aiming accuracy of 5.5°. The calculation method and analysis presented in this study can act as guidelines for future China LRRR emplacement missions. Lunar laser ranging (LLR) has the highest precision in measuring the earth-moon distance. The lunar laser ranging retro-reflector (LRRR) is an essential piece of equipment for realizing lunar laser ranging. China has plans to deploy a manually emplaced new generation LRRR. For the LRRR to work effectively, the azimuth and altitude angle of the LRRR must be adjusted such that the LRRR is aligned with the mean Earth direction. We established a method for calculating the adjustment angle of the LRRR and analyzed the misalignment caused by the biases of emplacement time and emplacement site. Results show that the aiming of error of the LRRR can be estimated at approximately 2.7°, and the maximum value is less than 5.0°, which satisfies the requirements for an aiming accuracy of 5.5°. The calculation method and analysis presented in this study can act as guidelines for future China LRRR emplacement missions.
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2024
- Vol. 61, Issue 7, 0706018 (2024)
Influence of Aero-Optical Effect on Laser Communication of Aircraft Platforms
Chenming Cao, Zhi Liu, Su Zhang, Peng Lin, Qingfang Jiang, and Helong Wang
To solve the problem of aero-optical effect of the aeronautical platform on the performance of the laser communication system of the aeronautical platform, the influence of the aero-optics effect on the optical transmission performance of the laser communication system is examined under the condition of different flight speeds and altitudes. The large eddy simulation method is used to simulate the aerodynamic flow field around the optical terminal of laser communication at different flight speeds and altitudes, the density change of the flow field is calculated, and the refractive index field is established according to the density data. Furthermore, the Runge-Kutta method is used to solve the beam equation, trace the beam, and calculate and analyze the optical path difference distribution and Strehl ratio of the whole field of view of the communication beam passing through the flow field. The simulation results show that as the flight speed increases, the change in flow field density becomes more intense, optical path difference increases gradually, and Strehl ratio decreases. In the case of the same speed, as the flight altitude increases, the flow field density fluctuation decreases, optical path difference decreases, and Strehl ratio increases. The results of this study are of guiding significance for compensating the aero-optical effect in the process of airborne laser communication and obtaining better communication quality. To solve the problem of aero-optical effect of the aeronautical platform on the performance of the laser communication system of the aeronautical platform, the influence of the aero-optics effect on the optical transmission performance of the laser communication system is examined under the condition of different flight speeds and altitudes. The large eddy simulation method is used to simulate the aerodynamic flow field around the optical terminal of laser communication at different flight speeds and altitudes, the density change of the flow field is calculated, and the refractive index field is established according to the density data. Furthermore, the Runge-Kutta method is used to solve the beam equation, trace the beam, and calculate and analyze the optical path difference distribution and Strehl ratio of the whole field of view of the communication beam passing through the flow field. The simulation results show that as the flight speed increases, the change in flow field density becomes more intense, optical path difference increases gradually, and Strehl ratio decreases. In the case of the same speed, as the flight altitude increases, the flow field density fluctuation decreases, optical path difference decreases, and Strehl ratio increases. The results of this study are of guiding significance for compensating the aero-optical effect in the process of airborne laser communication and obtaining better communication quality.
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2024
- Vol. 61, Issue 7, 0706017 (2024)
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.
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2024
- Vol. 61, Issue 7, 0706016 (2024)
Photocount Characteristics of SNSPD for PPM Signals in Deep-Space Laser Communication (Invited)
Xiaowei Wu, Lei Yang, Yueying Zhan, Yang Sun, Jiao Xiong, and Qiang Wang
Deep-space laser communication systems commonly use pulse-position modulation (PPM) to improve the energy efficiency of communication and use single-photon detectors for efficient signal reception. In particular, superconducting nanowire single-photon detectors (SNSPD) are one of the most suitable detector choices. In this study, we investigated the performance of high-speed PPM-SNSPD-based deep-space laser communications in terms of the dead time and jitter of SNSPD as well as the trailing phenomenon of high-speed pulsed signals. The photocount characteristics of SNSPD were analyzed. Based on this analysis, we proposed a bias-compensated guard-time PPM symbol synchronization algorithm. Compared with the conventional guard-time symbol synchronization algorithm, the proposed algorithm effectively reduces synchronization errors and improves system error performance. Deep-space laser communication systems commonly use pulse-position modulation (PPM) to improve the energy efficiency of communication and use single-photon detectors for efficient signal reception. In particular, superconducting nanowire single-photon detectors (SNSPD) are one of the most suitable detector choices. In this study, we investigated the performance of high-speed PPM-SNSPD-based deep-space laser communications in terms of the dead time and jitter of SNSPD as well as the trailing phenomenon of high-speed pulsed signals. The photocount characteristics of SNSPD were analyzed. Based on this analysis, we proposed a bias-compensated guard-time PPM symbol synchronization algorithm. Compared with the conventional guard-time symbol synchronization algorithm, the proposed algorithm effectively reduces synchronization errors and improves system error performance.
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2024
- Vol. 61, Issue 7, 0706015 (2024)
Compact Free-Running InGaAs/InP Single-Photon Detector for Real-Time Space Laser Communication (Invited)
Qixia Tong, Yong Lei, Xiangwei Shen, Chen Chen, Wei Chen, Jianglin Zhao, Li Ren, Dajian Cui, Liang Wang, and Shanyong Cai
In this study, to achieve high-speed, high-sensitivity, and low-cost laser communication, we optimized and improved a new InGaAs/InP single-photon avalanche diode (SPAD) to better apply to the near-infrared laser communication system detected using a single single-photon detector (SPD). Compared with the previous generation, we added a dielectric-metal reflective layer and improved the double Zn diffusion process while optimizing the structure of each layer. The fabricated InGaAs/InP SPAD achieved a photon detection efficiency (PDE) of 30%, a dark count rate (DCR) of 3 kHz, and an afterpulsing probability (Pap) of 2.4% under a high-frequency sine-wave gate (SWG) operating mode with a frequency of 1.25 GHz, temperature of 225 K, and bias of 6 V. A free-running negative feedback avalanche diode (NFAD) prepared based on the high-performance SPAD was used as a receiver in the real-time spatial laser communication system. The performance parameters of the laser communication system with the NFAD were experimentally obtained. The experimental results show that the InGaAs/InP NFAD with a bit rate of 1 Mbit/s using the 4-pulse position modulation (4PPM) scheme has a bit error rate of 1.1×10-5 and sensitivity of -69.6 dBm. In this study, to achieve high-speed, high-sensitivity, and low-cost laser communication, we optimized and improved a new InGaAs/InP single-photon avalanche diode (SPAD) to better apply to the near-infrared laser communication system detected using a single single-photon detector (SPD). Compared with the previous generation, we added a dielectric-metal reflective layer and improved the double Zn diffusion process while optimizing the structure of each layer. The fabricated InGaAs/InP SPAD achieved a photon detection efficiency (PDE) of 30%, a dark count rate (DCR) of 3 kHz, and an afterpulsing probability (Pap) of 2.4% under a high-frequency sine-wave gate (SWG) operating mode with a frequency of 1.25 GHz, temperature of 225 K, and bias of 6 V. A free-running negative feedback avalanche diode (NFAD) prepared based on the high-performance SPAD was used as a receiver in the real-time spatial laser communication system. The performance parameters of the laser communication system with the NFAD were experimentally obtained. The experimental results show that the InGaAs/InP NFAD with a bit rate of 1 Mbit/s using the 4-pulse position modulation (4PPM) scheme has a bit error rate of 1.1×10-5 and sensitivity of -69.6 dBm.
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2024
- Vol. 61, Issue 7, 0706014 (2024)
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.
Laser & Optoelectronics Progress
- Publication Date: Apr. 10, 2024
- Vol. 61, Issue 7, 0706013 (2024)
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