[1] Rong D D, Meng G, Fang X D et al. Delafossite AgAlO2 modified long-period grating for highly-sensitive ammonia sensor[J]. Optics Express, 29, 42005-42019(2021).

[2] Zhang Y X, Wang X X, Tang X Y et al. Photosensitive polymer-based micro-nano long-period fiber grating for refractive index sensing[J]. Journal of Lightwave Technology, 39, 6952-6957(2021).

[3] Sun M Y, Jiang H T, Shi B et al. Development of FBG salinity sensor coated with lamellar polyimide and experimental study on salinity measurement of gravel aquifer[J]. Measurement, 140, 526-537(2019).

[4] Xin X, Wu Y W, Liu H M et al. A new fabrication method of fiber Bragg grating hydrogen sensor[J]. Acta Optica Sinica, 41, 0406002(2021).

[5] Vengsarkar A M, Lemaire P J, Judkins J B et al. Long-period fiber gratings as band-rejection filters[J]. Journal of Lightwave Technology, 14, 58-65(1996).

[6] Rocha A M, Machado A I, Almeida T et al. Analysis of long period gratings inscribed by CO2 laser irradiation and estimation of the refractive index modulation[J]. Sensors, 20, 6409(2020).

[7] Ruan Z L, Pei L, Zheng J J et al. Intensity detecting refractive index sensors with long-period fiber gratings written in STS structure[J]. Chinese Optics Letters, 17, 070601(2019).

[8] Liu S, Zhou M, Zhang Z et al. Ultrasensitive refractometer based on helical long-period fiber grating near the dispersion turning point[J]. Optics Letters, 47, 2602-2605(2022).

[9] del Villar I. Ultrahigh-sensitivity sensors based on thin-film coated long period gratings with reduced diameter, in transition mode and near the dispersion turning point[J]. Optics Express, 23, 8389-8398(2015).

[10] Del Villar I, Cruz J L, Socorro A B et al. Sensitivity optimization with cladding-etched long period fiber gratings at the dispersion turning point[J]. Optics Express, 24, 17680-17685(2016).

[11] Dey T K, Tombelli S, Biswas P et al. Analysis of the lowest order cladding mode of long period fiber gratings near turn around point[J]. Journal of Lightwave Technology, 39, 4006-4012(2021).

[12] Zou F, Liu Y Q, Mou C B et al. Optimization of refractive index sensitivity in nanofilm-coated long-period fiber gratings near the dispersion turning point[J]. Journal of Lightwave Technology, 38, 889-897(2020).

[13] Zheng Z M, Yu Y S, Zhang X Y et al. Femtosecond laser inscribed small-period long-period fiber gratings with dual-parameter sensing[J]. IEEE Sensors Journal, 18, 1100-1103(2018).

[14] Viveiros D, de Almeida J M M M, Coelho L et al. Turn around point long period fiber gratings with coupling to asymmetric cladding modes fabricated by a femtosecond laser and coated with titanium dioxide[J]. Journal of Lightwave Technology, 39, 4784-4793(2021).

[15] Śmietana M, Mikulic P, Bock W J. Nano-coated long-period gratings for detection of sub-nanometric changes in thin-film thickness[J]. Sensors and Actuators A: Physical, 270, 79-83(2018).

[16] Tripathi S M, Bock W J, Mikulic P. A wide-range temperature immune refractive-index sensor using concatenated long-period-fiber-gratings[J]. Sensors and Actuators B: Chemical, 243, 1109-1114(2017).

[17] Huang T B, Shi J L, Pu J H et al. Long period gratings fabrication by arc discharge in photonic crystal fibers[J]. Acta Optica Sinica, 34, 0605002(2014).

[18] Ranjan R, Esposito F, Campopiano S et al. Sensing characteristics of arc-induced long period gratings in polarization-maintaining panda fiber[J]. IEEE Sensors Journal, 17, 6953-6959(2017).

[19] Colaço C, Caldas P, del Villar I et al. Arc-induced long-period fiber gratings in the dispersion turning points[J]. Journal of Lightwave Technology, 34, 4584-4590(2016).

[20] Rao Y J. The manufacture method and device of long period fiber grating[P].

[21] Du C, Wang Q, Zhao Y et al. Ultrasensitive long-period gratings sensor works near dispersion turning point and mode transition region by optimally designing a photonic crystal fiber[J]. Optics & Laser Technology, 112, 261-268(2019).

[22] Cui C L, Liu W P, Huang H B et al. Cladding mode's characteristic and its affects on transmission spectrum of long period fiber gratings[J]. Acta Photonica Sinica, 34, 1569-1572(2005).

[23] Ryu H S, Park Y, Oh S T et al. Effect of asymmetric stress relaxation on the polarization-dependent transmission characteristics of a CO2 laser-written long-period fiber grating[J]. Optics Letters, 28, 155-157(2003).