[1] Wang G, Pran K, Sagvolden G et al. Ship hull structure monitoring using fibre optic sensors[J]. Smart Materials and Structures, 10, 472-478(2001).

[2] Lu H L, Hu J H. High sensitivity curvature sensor based on SPS fiber structure[J]. Laser & Optoelectronics Progress, 56, 080601(2019).

[3] Xu R, Yurkewich A, Patel R V. Curvature, torsion, and force sensing in continuum robots using helically wrapped FBG sensors[J]. IEEE Robotics and Automation Letters, 1, 1052-1059(2016).

[4] Bai H D, Li S, Barreiros J et al. Stretchable distributed fiber-optic sensors[J]. Science, 370, 848-852(2020).

[5] Huang X C, Wu X W, Gao S C et al. Response characteristic of twisting second-azimuthal-order few-mode long-period fiber grating[J]. Chinese Journal of Lasers, 46, 1206001(2019).

[6] Yang K, Liu Y G, Wang Z et al. Twist sensor based on long period grating and tilted Bragg grating written in few-mode fibers[J]. IEEE Photonics Journal, 10, 1-8(2018).

[7] Yang K, Liu Y G, Wang Z et al. Fiber laser twist sensor with hybrid few-mode tilt Bragg grating and few-mode long period grating[J]. Optoelectronics Letters, 15, 161-164(2019).

[8] Li H Y, Rao B Y, Zhao X F et al. Development of fiber gratings inscribed by femtosecond laser[J]. Laser & Optoelectronics Progress, 57, 111420(2020).

[9] Fu H Y, Khijwania S K, Tam H Y et al. Polarization-maintaining photonic-crystal-fiber-based all-optical polarimetric torsion sensor[J]. Applied Optics, 49, 5954-5958(2010).

[10] Song B B, Miao Y P, Lin W et al. Multi-mode interferometer-based twist sensor with low temperature sensitivity employing square coreless fibers[J]. Optics Express, 21, 26806-26811(2013).

[11] Zhou Q, Zhang W G, Chen L et al. Fiber torsion sensor based on a twist taper in polarization-maintaining fiber[J]. Optics Express, 23, 23877-23886(2015).

[12] Kang X X, Zhang W G, Zhang Y X et al. Intensity-demodulated torsion sensor based on thin-core polarization-maintaining fiber[J]. Applied Optics, 57, 3474-3478(2018).

[13] Zhang H L, Wu Z F, Shum P P et al. Directional torsion and temperature discrimination based on a multicore fiber with a helical structure[J]. Optics Express, 26, 544-551(2018).

[14] Liu C, Jiang Y J, Du B B et al. Strain-insensitive twist and temperature sensor based on seven-core fiber[J]. Sensors and Actuators A: Physical, 290, 172-176(2019).

[15] Kim H M, Kim T H, Kim B et al. Temperature-insensitive torsion sensor with enhanced sensitivity by use of a highly birefringent photonic crystal fiber[J]. IEEE Photonics Technology Letters, 22, 1539-1541(2010).

[16] Chen W G, Lou S Q, Wang L W et al. Highly sensitive torsion sensor based on Sagnac interferometer using side-leakage photonic crystal fiber[J]. IEEE Photonics Technology Letters, 23, 1639-1641(2011).

[17] Liu D J, Wu Q, Han W et al. Strain independent twist sensor based on uneven platinum coated hollow core fiber structure[J]. Optics Express, 27, 19726-19736(2019).

[18] Lu H L, Yue Y L, Du J et al. Temperature and liquid refractive index sensor using P-D fiber structure-based Sagnac loop[J]. Optics Express, 26, 18920-18927(2018).