[1] WANG Yan-tao, JIANG Feng-xian, QIAO Yin-zhuang. Study on concentration measurement of ammonia nitrogen based on a cascaded fiber grating［J］. Optical Instruments, 2015, 37(3): 195-198.

[2] RUAN Juan, ZENG Qing-ke, QIN Zi-xiong,et al. Design on high sensitivity temperature sensors based on long-period fiber gratings［J］. Optical Instruments, 2008, 30(3): 26-29.

[3] NANDINI B, PALAS B, RICHARD M C, et al. Design of Palladium-Coated long-period fiber grating for hydrogen sensing［J］. Journal of Lightwave Technology, 2016, 34(21): 4912-4919.

[4] ZOU Fang, LIU Yun-qi, DENG Chuan-lu, et al. Refractive index sensitivity of nano-film coated long-period fiber gratings［J］. Optics Express, 2015, 23(2): 1114-1124.

[5] REES N D, JAMES S W, TATAM R P. Optical fiber long-period gratings with Langmuir-Blodgett thin-film overlays［J］. Optics Letters, 2002, 27(9): 686-688.

[6] VILLAR I D, MATIAS I R, ARREGUI F J. Optimization of sensitivity in Long Period Fiber Gratings with overlay deposition［J］. Optics Express, 2005, 13(1): 56-69.

[7] CUSANO A, IADICICCO A, PILLA P,et al. Cladding mode reorganization in high-refractive-index-coated long-period gratings: effects on the refractive-index sensitivity［J］. Optics Letters, 2005, 30(19): 2536-2538.

[8] YU Xiu-juan, ZHANG Min, WANG Li-wei, et al. Characteristics of long-period optical fiber grating with high refractive index nm-thick film overlay［J］. Acta Optica Sinica, 2009, 29(10): 2665-2672.

[9] PILLA P, TRONO C, BALDINI F, et al. Giant sensitivity of long period gratings in transition mode near the dispersion turning point: an integrated design approach［J］. Optics Letters, 2012, 37(19): 4152-4154.

[10] GU Zheng-tian, LAN Jing-long. Mode transition in absorption film coated long-period fiber grating and response characteristics of refractive index［J］. Acta Optica Sinica, 2013, 33(7): 0706003.

[11] GU Zheng-tian, LAN Jing-long. Design optimization of coated long-period fiber grating based on mode transition［J］. Chinese Journal of Lasers, 2014, 41(1): 0105007.

[12] GU Zheng-tian, LAN Jing-long. Mode transition and refractive index response in long-period fiber grating coated with double-layer overlays including mental film［J］. Acta Optica Sinica, 2014, 34(4): 0406005.

[13] CHEN Hai-yun, PENG Bao-jin, SI Jian-xiao,et al. Film sensor based on long-period fiber grating with reduced cladding［J］. Acta Photonica Sinica, 2016, 45(1): 0106003.

[14] LAN Jing-long, GU Zheng-tian. The study of characteristics of cladding-reduced coated long- period fiber grating based on mode transition and dual peak resonance［J］. Spectroscopy and Spectral Analysis, 2015, 35(11): 3230-3235.

[15] GU Zheng-tian, XU Yan-ping. Design optimization of a long-period fiber grating with sol–gel coating for a gas sensor［J］.Measurement Science and Technology, 2007, 18(11): 3530-3536.