[1] Li Y F, Liu J X, Zhao S S et al. An Φ-OTDR system combining frequency division multiplexing and polarization diversity technology[J]. Optoelectronic Technology, 41, 283-288(2021).

[2] Gao L G, Wang Y P, Tian X Z et al. Frequency division multiplexing fiber Bragg grating sensing system based on a dual-loop optoelectronic oscillator[J]. Acta Optica Sinica, 43, 2028002(2023).

[3] Jiang J, Rao Y J, Zhou C X et al. Frequency-multiplexed fiber-optic Fizeau strain sensor system based on optical amplification[J]. Acta Physica Sinica, 53, 2221-2225(2004).

[4] Sun K, Han Y, He M Y. High frequency vibration detection and demodulation based on frequency division multiplexing φ-OTDR[J]. Transducer and Microsystem Technologies, 42, 148-151(2023).

[5] Song X L, Peng F. Research on performance improvement of distributed fiber acoustic sensing system based on φ-OTDR[J]. Semiconductor Optoelectronics, 44, 609-615(2023).

[6] Bian X L, Jiang J J, Tong X et al. Multi-point partial discharge detection system based on Sagnac interferometer[J]. Laser & Infrared, 54, 154-160(2024).

[7] Guo S P, Gao Y Y, Xu L N et al. Partial discharges detection system based on fiber Fabry-Perot sensors[J]. Instrument Technique and Sensor, 61-64(2015).

[8] Li Y Y, Chen J, Pang F F et al. Scheme to improve SNR of demudulated signal by combining FDM and Φ-OTDR[J]. Optical Communication Technology, 42, 1-4(2018).

[9] Ruan J, Zhu Z J, Sun H et al. SNR improvement methods for phase-sensitive optical time-domain reflectometer for UHV DC control and protection system[J]. Chinese Journal of Lasers, 49, 0906005(2022).

[10] Li K, Gong Y D, Zhang Z. Research progress of φ-OTDR noise reduction processing[J]. Laser & Optoelectronics Progress, 59, 2300002(2022).

[11] Luo H Z, Liu S J, Gan Y J et al. An OTDR signal denoising algorithm based on CEEMDAN-improved wavelet threshold[J]. Journal of Optoelectronics·Laser, 33, 241-247(2022).

[12] Yu M, Zhang Y L, He Y T et al. Variational mode decomposition and permutation entropy method for denoising of distributed optical fiber vibration sensing system[J]. Acta Optica Sinica, 42, 0706005(2022).

[13] Chen H, Xu Y, Qian S et al. Distributed fiber-optic ultrasonic sensor applied in detection of discharging fault of power cable joint[J]. Acta Optica Sinica, 41, 0306001(2021).

[14] Zhang X N, Jing J W, Lin J et al. Noise reduction method of power cable partial discharge signal based on EMD-SVD[J]. Electronic Design Engineering, 31, 96-100(2023).

[15] Donoho D L. De-noising by soft-thresholding[J]. IEEE Transactions on Information Theory, 41, 613-627(1995).