Research on coherent differential absorption LiDAR based on Golay coding technology

Hu Yihua; Dong Xiao; Zhao Nanxiang

doi:10.12086/oee.2019.190081

Article navigation > Opto-Electronic Engineering > 2019 Vol. 46 > No. 7 > 19081-

Next Article Previous Article

Hu Yihua, Dong Xiao, Zhao Nanxiang. Research on coherent differential absorption LiDAR based on Golay coding technology[J]. Opto-Electronic Engineering, 2019, 46(7): 19081-. doi: 10.12086/oee.2019.190081

Citation:

Hu Yihua, Dong Xiao, Zhao Nanxiang. Research on coherent differential absorption LiDAR based on Golay coding technology[J]. Opto-Electronic Engineering, 2019, 46(7): 19081-. doi: 10.12086/oee.2019.190081

Research on coherent differential absorption LiDAR based on Golay coding technology

1.
State Key Laboratory of Pulsed Power Laser Technology, College of Electronic Engineering, National University of Defense Technology, Hefei, Anhui 230037, China
2.
Anhui Province Key Laboratory of Electronic Restriction Technology, College of Electronic Engineering, National University of Defense Technology, Hefei, Anhui 230037, China

Fund Project: Supported by National Natural Science Foundation of China (61871389) and Major Fund Program of National University of Defense Technology (ZK18-01-02)

More Information

^*Corresponding author: Dong Xiao, E-mail:skl_dongxiao@163.com

Received Date 01 March 2019

Revised Date 10 May 2019

Published Date 01 July 2019

Abstract

Abstract

The detection of CO₂ based on coherent different absorption LiDAR (CDIAL) requires high signal-to-noise ratio (SNR). To improve the SNR and reduce the inversion error of CO₂, a coherent differential absorption LiDAR based on Golay coding is proposed and the corresponding decoding method is also studied. The coding gain of SNR in traditional atmospheric backscattering signal detection is also analyzed when the pulse code technology is used. The variations of coding gain with the power of local oscillator (LO), the code length and the splitting ratio of 3 dB coupler are discussed. The higher the local oscillator power is and the more the beam splitting ratio deviates from 50%, the lower the coding gains. In addition, there are optimal code lengths in practical systems. The influence of thermal noise on the detection system decreases when the LO power grows, and there is optimal LO power which is only related to the system noise characteristics. The optimal LO power decreases with respect to single pulse detection after pulse coding, but the SNR is still higher than the traditional single pulse detection. When the splitting ratio of the 3 dB coupler is 0.495, the optimal LO power in coded system is 0.93 mW. The effective detection ranges of CO₂ increase when the pulses are coded, and in the pulse accumulations of 10⁴~10¹⁰, the improvement ratios of effective detection range are higher than 15%.
- coherent LiDAR /
- differential LiDAR /
- Golay coding /
- coding gain

FullText(HTML)

References

[1]	Ishii S, Koyama M, Baron P, et al. Ground-based integrated path coherent differential absorption lidar measurement of CO₂: foothill target return[J]. Atmospheric Measurement Techniques, 2013, 6(5): 1359-1369. doi: 10.5194/amt-6-1359-2013 CrossRef Google Scholar
[2]	Ishii S, Mizutani K, Fukuoka H, et al. Coherent 2μm differential absorption and wind lidar with conductively cooled laser and two-axis scanning device[J]. Applied Optics, 2010, 49(10): 1809-1817. doi: 10.1364/AO.49.001809 CrossRef Google Scholar
[3]	Gibert F, Edouart D, Cénac C, et al. 2-μm Ho emitter-based coherent DIAL for CO₂ profiling in the atmosphere[J]. Optics Letters, 2015, 40(13): 3093-3096. doi: 10.1364/OL.40.003093 CrossRef Google Scholar
[4]	Wu S H, Liu B Y, Liu J T, et al. Wind turbine wake visualization and characteristics analysis by Doppler lidar[J]. Optics Express, 2016, 24(10): A762-A780. doi: 10.1364/OE.24.00A762 CrossRef Google Scholar
[5]	Wang C, Xia H Y, Liu Y P, et al. Spatial resolution enhancement of coherent Doppler wind lidar using joint time-frequency analysis[J]. Optics Communications, 2018, 424: 48-53. doi: 10.1016/j.optcom.2018.04.042 CrossRef Google Scholar
[6]	Belmonte A. Analyzing the efficiency of a practical heterodyne lidar in the turbulent atmosphere: telescope parameters[J]. Optics Express, 2003, 11(17): 2041-2046. doi: 10.1364/OE.11.002041 CrossRef Google Scholar
[7]	Hu Y H, Dong X, Zhao N X, et al. System efficiency of heterodyne lidar with truncated Gaussian Schell-Model beam in turbulent atmosphere[J]. Optics Communications, 2019, 436: 82-89. doi: 10.1016/j.optcom.2018.12.008 CrossRef Google Scholar
[8]	Muanenda Y S, Taki M, Nannipieri T, et al. Advanced coding techniques for long-range raman/BOTDA distributed strain and temperature measurements[J]. Journal of Lightwave Technology, 2016, 34(2): 342-350. doi: 10.1109/JLT.2015.2493438 CrossRef Google Scholar
[9]	Wang F, Zhu C H, Cao C Q, et al. Enhancing the performance of BOTDR based on the combination of FFT technique and complementary coding[J]. Optics Express, 2017, 25(4): 3504-3513. doi: 10.1364/OE.25.003504 CrossRef Google Scholar
[10]	Nazarathy M, Newton S A, GIFFARD R P, et al. Real-time long range complementary correlation optical time domain reflectometer[J]. Journal of Lightwave Technology, 1989, 7(1): 24-38. doi: 10.1109/50.17729 CrossRef Google Scholar
[11]	周艳宗, 王冲, 魏天问, 等.基于Golay脉冲编码技术的相干激光雷达仿真研究[J].中国激光, 2018, 45(8): 810004. Google Scholar Zhou Y Z, Wang C, Wei T W, et al. Simulation research of coherent lidar based on golay coding technology[J]. Chinese Journal of Lasers, 2018, 45(8): 0810004. Google Scholar
[12]	杜晓林, 苏涛, 王旭, 等.基于Golay互补序列空时编码的MIMO雷达波形设计[J].电子与信息学报, 2014, 36(8): 1966-1971. Google Scholar Du X L, Su T, Wang X, et al. Golay complementary sequence with space time coding for MIMO radar waveform design[J]. Journal of Electronics & Information Technology, 2014, 36(8): 1966-1971. Google Scholar
[13]	Pezeshki A, Calderbank R A, Moran W, et al. Doppler resilient golay complementary waveforms[J]. IEEE Transactions on Information Theory, 2008, 54(9): 4254-4266. doi: 10.1109/TIT.2008.928292 CrossRef Google Scholar
[14]	Hu Y H, Dong X, Guo L R. Coherent detection of backscattered polarized laser with polarization diversity reception[C]//Proceedings of the 4th International Conference on Ubiquitous Positioning, Indoor Navigation and Location Based Services, Shanghai, 2016: 271-277.https://www.researchgate.net/publication/312184310_Coherent_detection_of_backscattered_polarized_laser_with_polarization_diversity_reception Google Scholar
[15]	李永倩, 王文平, 李晓娟, 等. APD检测Golay编码BOTDR系统的建模分析与优化设计[J].红外与激光工程, 2017, 46(11): 1122002. Google Scholar Li Y Q, Wang W P, Li X J, et al. Modeling analysis and optimization design of a Golay coding Brillouin Optical Time Domain Reflectometer system with APD detector[J]. Infrared and Laser Engineering, 2017, 46(11): 1122002. Google Scholar
[16]	杨彦玲, 李彦超, 高龙, 等.相干激光雷达平衡外差探测方法的数值仿真[J].红外与激光工程, 2011, 40(10): 1918-1922. doi: 10.3969/j.issn.1007-2276.2011.10.018 CrossRef Google Scholar Yang Y L, Li Y C, Gao L, et al. Numerical simulation of balanced heterodyne detection for coherent lidar[J]. Infrared and Laser Engineering, 2011, 40(10): 1918-1922. doi: 10.3969/j.issn.1007-2276.2011.10.018 CrossRef Google Scholar
[17]	Holmes J F, Rask B J. Optimum optical local oscillator power levels in coherent detection systems[J]. Proceedings of SPIE, 1993, 1982: 157-63. doi: 10.1117/12.142009 CrossRef Google Scholar
[18]	Frehlich R G, Kavaya M J. Coherent laser radar performance for general atmospheric refractive turbulence[J]. Applied Optics, 1991, 30(36): 5325-5352. doi: 10.1364/AO.30.005325 CrossRef Google Scholar
[19]	Ren Y X, Dang A H, Liu L, et al. Heterodyne efficiency of a coherent free-space optical communication model through atmospheric turbulence[J]. Applied Optics, 2012, 51(30): 7246-7254. doi: 10.1364/AO.51.007246 CrossRef Google Scholar
[20]	Dong X, Hu Y, Zhao N, et al. Numerical analysis of linewidth demands in heterodyne lidar[C]//Proceedings of the Advanced Sensor Systems and Applications VIII, Beijing, 2018: 1082113. Google Scholar
[21]	Hu Y H, Dong X, Zhao N X, et al. Fast retrieval of atmospheric CO₂ concentration based on a near-infrared all-fiber integrated path coherent differential absorption lidar[J]. Infrared Physics & Technology, 2018, 92: 429-435. Google Scholar

Overview

Overview

Overview: The differential absorption LiDAR (DIAL) can obtain the spatio-temporal distribution information of atmospheric CO₂, which needs high signal-to-noise ratio (SNR). To improve the detection SNR, the coherent detection and heterodyne detection are widely used and have been combined with DIAL due to the excellent noise-reducing ability. In this paper, we propose a coherent differential absorption LiDAR (CDIAL) based on Golay coding to further reduce the detection errors, and the decoding method is also analyzed. The coding gain formula of SNR due to Golay coding is deduced, which is related to the local oscillator (LO) power, the code length, the splitting ratio of the 3 dB coupler. When the LO power is lower, the thermal noise should not be neglected, and the coding gain is higher, which is mainly due to the suppression of thermal noise. The higher the local oscillator power is and the more the beam splitting ratio deviates from 50%, the lower the coding gains are, because these two factors can improve the shot noise and the relative intensity noise, and thus the influence of thermal noise decreases. In addition, there are optimal code lengths in actual heterodyne detection systems, when the code length is higher than the optimal code length, the increase of coding gain is not obvious. The influence of thermal noise on the detection system decreases when the LO power grows, and there are optimal LO power which is only related to the system noise characteristics. The optimal LO power decreases with respect to single pulse detection after pulse coding, but the SNR is still higher than the traditional single pulse detection. When the splitting ratio of the 3 dB coupler is 0.495, the optimal LO power in coded system is 0.93 mW, and the maximum SNR in traditional pulse LiDARs is 73.27% of that in coded pulse LiDARs. When the splitting ratio is 0.49, the optimal LO power can be further lower. To analyze the improvement of CDIAL performance when the Golay coding is used, we calculate the detection error of CDIAL under different LO power. Two operation mode of CDIAL system are considered, including the collimated mode and the focused mode. The focused mode has better performance in short range detection duo to its relatively higher system efficiency. The detection accuracy of CO2 should be better than 4 ppm, and we define the range corresponding the error of 4 ppm as the effective range. And the effective range is longer with the coded pulses. In the pulse accumulations of 104~1010, the improvement ratios of effective detection range are higher than 15%. In addition, the Golay coding technology can both improve the SNR and the spatial resolution of LiDARs, which will be discussed in the future research.