[1] Yoon M S, Kim H J, Kim S J et al. Influence of the waist diameters on transmission characteristics and strain sensitivity of microtapered long-period fiber gratings[J]. Optics Letters, 38, 2669-2672(2013).

[2] Rao Y J, Wang Y P, Ran Z L et al. Novel fiber-optic sensors based on long-period fiber gratings written by high-frequency CO2 laser pulses[J]. Journal of Lightwave Technology, 21, 1320-1327(2003).

[3] Wang Y, Wang D, Jin W et al. Asymmetric long period fiber gratings fabricated by use of CO2 laser to carve periodic grooves on the optical fiber[J]. Applied Physics Letters, 89, 151105(2006).

[4] Shi S H, Wang X, Zhao M F et al. Sensing characteristics of long period fiber grating functionalized with graphite oxide[J]. Optics and Precision Engineering, 27, 2305-2314(2019).

[5] Jiao D L, Guo W J, Bo X N et al. Simultaneous measurement of temperature and refractive index using a single dual-period fiber grating[J]. Optical Technique, 45, 458-462(2019).

[6] Zhu Y Y, Xi Y R, Zhang Y N et al. Numerical simulation of transmission spectra characterization of long-period fiber grating[J]. Chinese Optics, 13, 451-458(2020).

[7] Xue Y R, Tian P F, Jin W et al. Superimposed long period gratings based mode converter in few-mode fiber[J]. Acta Physica Sinica, 68, 20181674(2019).

[8] Shao L Y, Zhao J, Dong X Y et al. Long-period grating fabricated by periodically tapering standard single-mode fiber[J]. Applied Optics, 47, 1549-1552(2008).

[9] Caldas P, Rego G, Ivanov O V et al. Characterization of the response of a dual resonance of an arc-induced long-period grating to various physical parameters[J]. Applied Optics, 49, 2994-2999(2010).

[10] Grubsky V, Feinberg J. Fabrication of axially symmetric long-period gratings with a carbon dioxide laser[J]. IEEE Photonics Technology Letters, 18, 2296-2298(2006).

[11] Yin G L, Wang Y P, Liao C R et al. Long period fiber gratings inscribed by periodically tapering a fiber[J]. IEEE Photonics Technology Letters, 26, 698-701(2014).

[12] Jin X R, Sun C T, Duan S J et al. High strain sensitivity temperature sensor based on a secondary modulated tapered long period fiber grating[J]. IEEE Photonics Journal, 11, 7100908(2019).

[13] Liu J H, Cheng M H, Kong X D et al. Microtapered long period gratings: non-destructive fabrication, highly sensitive torsion sensing, and tunable broadband filtering[J]. Infrared Physics & Technology, 102, 103000(2019).

[14] Linesh J, Libish T M, Bobby M C et al. Periodically tapered LPFG for ethanol concentration detection in ethanol-gasoline blend[J]. Sensors & Transducers, 125, 205-212(2011).

[15] Zeng H Y, Geng T, Yang W L et al. Combining two types of gratings for simultaneous strain and temperature measurement[J]. IEEE Photonics Technology Letters, 28, 477-480(2016).

[16] Kong X D, Ren K L, Ren L Y et al. Tunable wavelength-selective coupler based on microtapered long-period fiber gratings[J]. IEEE Photonics Technology Letters, 30, 821-824(2018).

[17] Shi J M, Zheng D, Pan W et al. Fiber grating ultrasonic sensor based on coupling cone structure and its application in nondestructive detection[J]. Acta Optica Sinica, 39, 1206004(2019).

[18] Ren K L, Ren L Y, Liang J et al. Highly strain and bending sensitive microtapered long-period fiber gratings[J]. IEEE Photonics Technology Letters, 29, 1085-1088(2017).

[19] Geng J, Zhu X J, Zhang G A et al. Bandwidth tunable microfiber-assisted Mach-Zehnder interferometer based on tapered-drawing fiber Bragg grating[J]. Acta Optica Sinica, 39, 0306004(2019).

[20] Yoon M S, Park S, Han Y G. Simultaneous measurement of strain and temperature by using a micro-tapered fiber grating[J]. Journal of Lightwave Technology, 30, 1156-1160(2012).

[21] Shin W, Yu B A, Noh Y C et al. Bandwidth-tunable band-rejection filter based on helicoidal fiber grating pair of opposite helicities[J]. Optics Letters, 32, 1214-1216(2007).

[22] Zhu C L, Zhao H, Wang P et al. Enhanced flat-top band-rejection filter based on reflective helical long-period fiber gratings[J]. IEEE Photonics Technology Letters, 29, 964-966(2017).