[1] [1] LI S C, LIU K, JIANG J F, et al. A denoising and positioning method of long-distance fiber optic perimeter security system based on -OTDR[C]//SPIE. Proceedings of 2021 International Conference on Optical Instruments and Technology: Optical Sensors and Applications. Bellingham: SPIE, 2022: 190-200.

[2] [2] LI Z X, WANG Z Q, LI J H et al. Technology research of -OTDR fiber perimeter intrusion system based on CNN-LSTM algorithm[C]//SPIE. Proceedings of Third International Conference on Advanced Algo rithms and Neural Networks (AANN 2023). Bellingham: SPIE, 2023: 98-105.

[3] [3] TOMASOV A, ZAVISKA P, SPURNY V, et al. Enhancing perimeter protection using -OTDR and CNN for event classification[C]//Optica Publishing Group. Proceedings of 28th International Conference on Optical Fiber Sensors. Washington: Optica Publishing Group, 2023: W4.39-1-W4. 39-4.

[4] [4] LI G, ZENG K H, ZHOU B, et al. Vibration monitoring for the west-east gas pipeline project of China by phase optical time domain reflectometry (phase-OTDR)[J]. Instrumentation Science & Technology, 2021, 49(1): 65-80.

[5] [5] LALAM N, WESTBROOK P, NAEEM K, et al. Pilot-scale testing of natural gas pipeline monitoring based on phase-OTDR and enhanced scatter optical fiber cable[J]. Scientific Reports, 2023, 13(1): 14037-1-14037-12.

[6] [6] ZHANG S, XIONG Z J, JI B Y, et al. Water pipeline leakage detection based on coherent -OTDR and deep learning technology[J]. Applied Sciences, 2024, 14(9): 3814-3826.

[7] [7] ZHU P, WEN H Q, CHE Q, et al. Disturbed partial discharge detection system based on an improved -OTDR assisted by a FBG array[J]. Applied Optics, 2020, 59(14): 4367-4370.

[8] [8] DING Z W, ZHANG X P, ZOU N M, et al. Phi-OTDR based on-line monitoring of overhead power transmission line[J]. Journal of Lightwave Technology, 2021, 39(15): 5163-5169.

[9] [9] LIU Z H, YANG S, CHEN Q, et al. Partial discharge distributed locating in power cable joints using -OTDR optical fiber system[J]. IEEE Sensors Journal, 2024, 24(9):14404-14412.

[10] [10] FILOGRANO M L, RIZIOTIS C, KANDYLA M. A low-cost phase-OTDR system for structural health monitoring: design and instrumentation[J]. Instruments, 2019, 3(3): 46-62.

[11] [11] ZAHOOR R, CERRI E, VALLIFUOCO R, et al. Lamb wave detection for structural health monitoring using a -OTDR system[J]. Sensors, 2022, 22(16): 5962-5972.

[12] [12] VALLIFUOCO R, CERRI E, MINARDO A, et al. Lamb waves detection through phi-OTDR for structural health monitoring[C]//IEEE. Proceedings of 2022 IEEE 9th International Workshop on Metrology for AeroSpace (MetroAeroSpace). New York: IEEE, 2022: 346-350.

[13] [13] GU J F, LU B, YANG J Q, et al. High SNR -OTDR based on frequency and wavelength diversity with differential vector aggregation method[J]. IEEE Photonics Journal, 2020, 12(6): 1-12.

[14] [14] QIAN H, LUO B, HE H J, et al. Fading-free -OTDR with multi-frequency decomposition[J]. IEEE Sensors Journal, 2021, 22(3): 2160-2166.

[15] [15] ZABIHI M, KREBBER K. Laser source frequency drift compensation in -OTDR systems using multiple probe frequencies[J]. Optics Express, 2022, 30(11): 19990-19998.

[16] [16] ZHAO Z Y, WU H, HU J H, et al. Interference fading suppression in -OTDR using space-division multiplexed probes[J]. Optics Express, 2021, 29(10): 15452-15462.

[17] [17] ZHANG Y X, LIU J X, XIONG F, et al. A space-division multiplexing method for fading noise suppression in the -OTDR system[J]. Sensors, 2021, 21(5): 1694-1709.

[18] [18] WANGT Y, MA Z, ZHANG J Z, et al. Performance improvement of -OTDR systems by 3×3 coupler dual-end detection scheme[J]. Journal of Lightwave Technology, 2024.

[19] [19] YUAN Q, WANG F, LIU T, et al. Using an auxiliary Mach-Zehnder interferometer to compensate for the influence of laser-frequency-drift in -OTDR[J]. IEEE Photonics Journal, 2018, 11(1): 1-9.

[20] [20] ZHANG J M, YAN Y X, LIU S Q, et al. Signal-to-noise ratio enhancement of -OTDR based on block-matching and 3D filtering[C]//IEEE. Proceedings of 2023 Opto-Electronics and Communications Conference (OECC). New York: IEEE, 2023: 1-3.

[21] [21] MA Q L, GAO X, GAO Y, et al. A study on noise reduction of -OTDR system based on VSS-NLMS algorithm[J]. IEEE Sensors Journal, 2021, 21(6): 7648-7656.

[22] [22] CHEN Y F, ZHU S H, YU K M, et al. Quantitative analysis of -OTDR spatial resolution influenced by NLM parameters[J]. Photonics, 2023, 10(5): 529-538.

[23] [23] WANG P F, LV Y J, WANG Y, et al. Adaptability and anti-noise capacity enhancement for -OTDR with deep learning[J]. Journal of Lightwave Technology, 2020, 38(23): 6699-6706.

[24] [24] LI S C, LIU K, JIANG J F, et al. An ameliorated denoising scheme based on deep learning for -OTDR system with 41-km detection range[J]. IEEE Sensors Journal, 2022, 22(20): 19666-19674.

[25] [25] LI J C, WANG Y, LIU X, et al. SNR improvement for -OTDR with sparse representation denoising method[J]. Optical Fiber Technology, 2023, 76: 103231-1-103231-9.

[26] [26] ZHANG Y X, ZHOU T, DING Z W, et al. Classification of inter-ferencefading tolerant -OTDR signal using optimal peak-seeking and machine learning[J]. Chinese OpticsLetters, 2021, 19(3): 030601-1-030601-5.

[27] [27] ZHAO L J, ZHANG X Z, XU Z N, et al. Influencing Factors of IQ demodulation method in distributed acoustic sensors[J]. Acta Optica Sinica, 2023, 43(14): 1428001-1-1428001-16.

[28] [28] WANG X, LIU M H, YU M, et al. Analysis and improvement for digital quadrature demodulation algorithm on phase-sensitive optical time-domain reflectometric system[J]. Chinese Journal of Lasers, 2017, 44(12): 1210002-1-1210002-7.

[29] [29] WU Y, WANG Z N, XIONG J, et al. Interference fading elimination with single rectangular pulse in -OTDR[J]. Journal of Lightwave Technology, 2019, 37(13): 3381-3387.

[30] [30] QIAN H, CUI M J, LI Y N, et al. Phase demodulation under ultra-low sampling rate in heterodyne coherent -OTDR[J]. Infrared Physics & Technology, 2024, 143: 105597-1-105597-7.

[31] [31] AMOROSO F. The bandwidth of digital data signal[J]. IEEE Communications Magazine, 1980, 18(6): 13-24.