[1] [1] LIU Y, CHOUDHARY A, MARPAUNG D, et al. Integrated microwave photonic filters［J］. Advances in Optics and Photonics, 2020, 12(2):485-555.

[2] [2] ZHAO Y, SONG T T, HUO Z W. Tunable optical fiber filter based on a fiber Bragg grating loop mirror［J］. Journal of Lightwave Technology, 2011, 29(24):3672-3675.

[3] [3] SOREF R A, DE LEONARDIS F, PASSARO V M N. Multiple-Sagnac loop Mach-Zehnder interferometer for wavelength interleaving, thermo-optical switching and matched filteri［J］. Journal of Lightwave Technology, 2018, 36(22):5254-5262.

[4] [4] JIANG X, WU J, YANG Y, et al. Wavelength and bandwidth-tunable silicon comb filter based on Sagnac loop mirrors with Mach-Zehnder interferometer couplers［J］. Optics express, 2016, 24(3):2183-2188.

[5] [5] KIM C S, SOVA R M, KANG J U. Tunable multi-wavelength all-fiber Raman source using fiber Sagnac loop filter［J］. Optics Communications, 2003, 218(4-6):291-295.

[6] [6] LIU X, LOU S, TANG Z, et al. Tunable dual-wavelength ytterbium-doped fiber ring laser based on a Sagnac interferometer［J］. Optics & Laser Technology, 2019, 116:37-42.

[7] [7] ZHOU X, ZHOU Y, LI Z, et al. Research on temperature sensing characteristics with cascaded fiber Sagnac interferometer and fiber Fabry-Perot interferometer-based fiber laser［J］. Optical Engineering, 2019, 58(5):057103.

[8] [8] GONZAlEZ-GARCIA A, POTTIEZ O, GRAJALES-COUTINO R, et al. Switchable and tuneable multi-wavelength Er-doped fibre ring laser using Sagnac filters［J］. Laser Physics, 2010, 20:720-725.

[9] [9] LIN W, SHAO L, LIU Y, et al. Temperature sensor based on fiber ring laser with cascaded fiber optic Sagnac interferometers［J］. IEEE Photonics Journal, 2021, 13(2):1-12.

[10] [10] MᶏDRY M, BERES-PAWLIK E. Intensity-modulated Sagnac loop temperature sensor setup［J］. Microwave and Optical Technology Letters, 2019, 61(5):1166-1170.

[11] [11] WANG S, LU P, MAO L, et al. Cascaded interferometers structure based on dual-pass Mach-Zehnder interferometer and Sagnac interferometer for dual-parameter sensing［J］. Optics Express, 2015, 23(2):674-680.

[12] [12] ZOU H, LOU S, YIN G, et al. Switchable dual-wavelength PM-EDF ring laser based on a novel filter［J］. IEEE Photonics Technology Letters, 2013, 25(11):1003-1006.

[13] [13] CHENG J, CHEN W, CHEN G. Switchable quadruple-wavelength Erbium-doped fiber laser based on a chirped fiber grating and polarization-maintaining fiber［J］. Optics & Laser Technology, 2016, 78:71-73.

[14] [14] DING Z, WANG Z, ZHAO C, et al. Tunable erbium-doped fiber laser based on optical fiber Sagnac interference loop with angle shift spliced polarization maintaining fibers［J］. Optical Fiber Technology, 2018, 42(5):1-5.

[18] [18] ERDOGAN T. Fiber grating spectra［J］. IEEE Lightwave Technology,1997,15(8):1277-1294.