[1] [1] DIANA V, JOEL P C, LUIS C, et al. Long-period grating fiber sensor with in situ optical source for remote sensing［J］. IEEE Photonics Technology Letters, 2010, 22(20): 1533-1535.

[2] [2] VENGSARKAR A M, PEDRAZZANI J R, JUDKINS J B, et al. Long-period fiber grating basen gain equalizers［J］. Optics Letter, 1996, 21(5): 336-338.

[3] [3] WU Min, RAO Yun-jiang, RAN Zeng-ling, et al. A long distance FBG sensor system based on LPFG denoising and hybrid amplification［J］. Journal of Optoelectronics Laser, 2007, 18(11): 1289-1292.

[4] [4] VENGSARKAR A M, LEMAIRE P J, JUDKINS J B, et al. Long period fiber gratings as band reject ion filters［J］. Journal Light wave Technology, 1996, 14(1): 58 -65.

[5] [5] ALLSOP T, KALLI K, ZHOU K, LAI Y, et al. Long period gratings written into a photonic crystal fibre by a femtosecond laser as directional bend sensors［J］. Optics Communications, 2008, 281(20): 5092-5096.

[6] [6] KONDO Y, NOUCHI K, MITSUYU T, et al. Fabrication of long-period fiber gratings by focused irradiation of infrared femtosecond laser pulses［J］. Optics Letters, 1999, 24(10): 646-648.

[7] [7] MARTINEZ A, DUBOV M, KHRUSHCHEV I, et al. Photo induced modifications in fiber gratings inscribed directly by infrared femtosecond irradiation［J］. IEEE Photonics Technology Letters, 2006, 18(21): 2266-2268.

[8] [8] MARTINEZ A, KHRUSHCHEV I Y, BENNION I. Direct inscription of Bragg gratings in coated fibers by an infrared femto-second laser［J］. Optics Letters, 2006, 31(11): 1603-1605.

[9] [9] ZHANG N, YANG J J, WANG M W, et al. Fabrication of long-period fiber gratings using 800 nm femtosecond laser pulses［J］. Chinese Physics Letters, 2006, 23(12): 3281-3284.

[11] [11] KONDO Y, NOUCHI K, MITSUYU T, et al. Fabrication of long-period fiber gratings by focused irradiation of infrared femtosecond laser pulses［J］. Optics Letters, 1999, 24(10): 646-648.

[12] [12] FUJII T, FUKUDA T, ISHIKAWA S, et al. Characteristics improvement of long-period fiber gratings fabricated by femtosecond laser pulses using novel positioning technique ［C］. Proceedings of Optical Fiber Communication Conference, Technical Digest (CD) , 2004, THC6.

[13] [13] ALEXEY I K, DAVID N, GILBERTO B. Long-period fiber grating fabrication by high-intensity femtosecond pulses at 211 nm［J］. Journal of Lightwave Technology, 2005, 23(8): 2568-2578.

[14] [14] ZHU Tao, RAO Yun-jiang, MO Qiu-ju. Ultra-long period fiber grating written by high-frequency CO2 laser pulses［J］. Acta Photonics Sinica, 2005, 34(1): 1697-1700.

[15] [15] RAO Yun-jiang, WANG Yi-ping, ZHU Tao. The principle and application of fiber Bragg grating［M］. 2006, Beijing: Science Press.

[16] [16] HU Y W, SUNX Y, DUAN J A, et al. The effect of refractive index modification position and duty cycle on performance of LPFGs［A］. In: Photonics and Optic electronics (SOPO)［C］, Wuhan, 2011: 1-3.

[17] [17] ZHANG Guo-sheng, MA Ren-de, WANG Zheng-ping, et al. Theoretical analysis of the influence of duty cycle on the spectrum distribution of long period fiber gratings［J］. Journal of Harbin Engineering University, 2007, 28(11): 1296-1300.

[18] [18] STEPHEN A S, DAVID N N. Long-period fiber grating inscription under high intensity 352 nm femto-second irradiation: Three photo absorption and energy deposition in cladding［J］. Optics Communications, 2005, 255: 81-90.

[19] [19] LI Chuan, ZHANG Yi-mo, ZHAO Yong-gui. Fiber grating: principle, technology and application［M］. 2005, Beijing: Science Press.