[1] He Z Y, Liu Q W. Optical fiber distributed acoustic sensors: a review[J]. Journal of Lightwave Technology, 39, 3671-3686(2021).

[2] Bao X Y, Zhou D P, Baker C et al. Recent development in the distributed fiber optic acoustic and ultrasonic detection[J]. Journal of Lightwave Technology, 35, 3256-3267(2017).

[3] Liu S Q, Yu F H, Hong R et al. Advances in phase-sensitive optical time-domain reflectometry[J]. Opto-Electronic Advances, 5, 200078(2022).

[4] 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, 43, 1428001(2023).

[5] Xia L, Wang X Y, Wu S B et al. On-line monitoring of optical waveguide micro-structure fabricated with femtosecond laser direct writing based on OCDR[J]. Chinese Journal of Lasers, 50, 1602402(2023).

[6] Wang H P. Influence of interfacial effect between distributed optical fiber sensors and monitored structures[J]. Acta Optica Sinica, 42, 0206004(2022).

[7] Wang Y, Xiao D, Niu Y Y et al. Structural deformation of fiber optic hydrophone probe based on optical frequency domain reflectometry[J]. Acta Optica Sinica, 43, 0528001(2023).

[8] Bai Y X, Lin T T, Zhong Z C. Noise reduction method of Φ-OTDR system based on EMD-TFPF algorithm[J]. IEEE Sensors Journal, 21, 24084-24089(2021).

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

[10] Qin Z G, Chen L, Bao X Y. Wavelet denoising method for improving detection performance of distributed vibration sensor[J]. IEEE Photonics Technology Letters, 24, 542-544(2012).

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

[12] Li J, Cheng C K, Jiang T Y et al. Wavelet de-noising of partial discharge signals based on genetic adaptive threshold estimation[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 19, 543-549(2012).

[13] Fan X L, Xie W C, Jiang W B et al. An improved threshold function method for power quality disturbance signal de-noising based on stationary wavelet transform[J]. Transactions of China Electrotechnical Society, 31, 219-226(2016).

[14] Langston C A, Mousavi S M. Separating signal from noise and from other signal using nonlinear thresholding and scale-time windowing of continuous wavelet transforms[J]. Bulletin of the Seismological Society of America, 109, 1691-1700(2019).

[15] Zheng S, Ma H T, Li Y. Reduction of seismic random noise in mountainous metallic mines based on adaptive threshold RCSST[J]. Chinese Journal of Geophysics, 62, 4020-4027(2019).

[16] Liu J C, Gu Y, Chou Y X et al. Seismic random noise reduction using adaptive threshold combined scale and directional characteristics of shearlet transform[J]. IEEE Geoscience and Remote Sensing Letters, 17, 1637-1641(2020).

[17] Lu J Y, Lin H, Ye D et al. A new wavelet threshold function and denoising application[J]. Mathematical Problems in Engineering, 2016, 3195492(2016).

[18] Zuo L Q, Sun H M, Mao Q C et al. Noise suppression method of microseismic signal based on complementary ensemble empirical mode decomposition and wavelet packet threshold[J]. IEEE Access, 7, 176504-176513(2019).

[19] Lu X, Krebber K. Characterizing detection noise in phase-sensitive optical time domain reflectometry[J]. Optics Express, 29, 18791-18806(2021).

[20] Graffeuil J, Liman R A, Muraro J L et al. Cyclostationary shot-noise measurements in RF Schottky-barrier diode detectors[J]. IEEE Electron Device Letters, 31, 74-76(2010).

[21] Goldberg L, Taylor H F, Weller J F. Feedback effects in a laser diode due to Rayleigh backscattering from an optical fibre[J]. Electronics Letters, 18, 353-354(1982).