title: Spectrum evolution of cascaded mismatching long-period fiber gratings.
abstract: Two identical long-period fiber gratings (LPFGs) are difficult to produce in practice, notably for CO(2)-laser or arc-discharge induced LPFGs. So it is meaningful to study the spectrum evolution of cascaded LPFGs with some deviation, named "mismatching" LPFGs. Theory and experiment demonstrate that the upper envelope of the fringe pattern is intrinsically curved but less dramatically than the lower envelope. Bending the grating pair to introduce proper cladding-mode loss can improve the contrast of the fringe pattern at a desired wavelength, which indicates that cascaded mismatching LPFGs can be used as high-quality comb filters or fiber sensors.
authors.affiliation: Department of Physics, Key Laboratory for Laser Plasmas (Ministry of Education), State Key Lab of Advanced Optical Communication Systems and Networks, Shanghai Jiao Tong University, Shanghai, 200240, China.
authors.forename: Xuesong
authors.initials: X
authors.lastname: Liu
authors.forename: Li
authors.initials: L
authors.lastname: Zhan
authors.forename: Shouyu
authors.initials: S
authors.lastname: Luo
authors.forename: Zhaochang
authors.initials: Z
authors.lastname: Gu
authors.forename: Jinmei
authors.initials: J
authors.lastname: Liu
authors.forename: Qishun
authors.initials: Q
authors.lastname: Shen