[1] [1] NYARKO B O, ADEKOYA A F, WEYORI B A. Predicting the actual location of faults in underground optical networks using linear regression[J]. Engineering reports, 2021, 3(2)：e12304.

[2] [2] NAKAMURA A, OHASHI M, ODA T, et al. Simple technique for measuring optical properties of randomly coupled multi-core fiber using OTDR[J]. IEICE communications express, 2020, 10(3)：177-185.

[3] [3] CHEN S L, YE C G, CHEN S B. Automatic monitoring system for dumping site slope based on OTDR & GBMS[J]. Dam and safety, 2020(1)：26-31. (in Chinese)

[4] [4] EGOR L, DANIEL G, SHMUEL S. Detuned Brillouin amplification of OTDR signals with an enhanced signal- to-noise ratio[J]. Optics letters, 2017, 42(27) ： 5166-5169.

[5] [5] MOSHE N, STEVEN A N, ROBIN P G, et al. Real-time long range complementary correlation optical time domain reflectometer[J]. Journal of lightwave technology, 1989, 7(1)：24-38.

[6] [6] SAHU P K, GOWRE S C, MAHAPATRA S. Optical time-domain reflectometer performance improvement using complementary correlated prometheus orthonormal sequence[J]. IET optoelectron, 2008, 2(3)：128-133.

[7] [7] IIDA H, KOSHIKIYA Y, ITO F, et al. High sensitivity coherent optical time domain reflectometry employing frequency division multiplexing[J]. Journal of lightwave technology, 2012, 30(8)：1121-1126.

[8] [8] RENATA G, AMOS A, MOSHE N. Direct detection and coherent optical time-domain reflectometry with Golay complementary codes[J]. Journal of lightwave technology, 2013, 31(13)：2207-2222.

[9] [9] JONES M D. Using simplex codes to improve OTDR sensitivity[J]. IEEE photonics technology letters, 1993, 5(7)：822-824.

[10] [10] ZHANG X P, QIAO W Y, SUN Z H, et al. A distributed optical fiber sensing system for synchronous vibration and loss measurement[J]. Optoelectronics letters, 2016, 12(5)：375-377.

[11] [11] ZHANG F, QI Y F, LI W. Using optical differential phase-shift keying to solve the bipolarity problem of spreading code in optical time domain reflectometer[J]. Results in physics, 2019, 13：102096.

[12] [12] QIAO Y Z, LU Z H, YAN B L, et al. Performance of differential phase shift keying maritime laser communication over log-normal distribution turbulence channel[J]. Optoelectronics letters, 2021, 17(2)：90-95.

[13] [13] SHIEH W, YANG Q, MA Y. 107 Gb/s coherent optical OFDM transmission over 1000-km SSMF fiber using orthogonal band multiplexing[J]. Optics express, 2008, 16(9)：6378-6386.

[14] [14] FATEMEH S, DAVID P, MICHA?L M, et al. DPSK modulation with a dual-drive silicon photonic loop-mirror modulator[J]. IEEE photonics technology letters, 2019, 31(13)：1037-1040.