title: Small-period long-period fiber grating with improved refractive index sensitivity and dual-parameter sensing ability.
abstract: We UV inscribe and characterize a long-period fiber grating with a period of 25 μm. A series of polarization-dependent dual-peak pairs can be seen in the transmission spectrum, even though only the symmetrical refractive index modification is introduced. The fabricated grating exhibits a lower temperature sensitivity compared with standard long-period gratings and an enhanced refractive index sensitivity of ∼312.5  nm/RIU averaged from 1.315 to 1.395, which is more than four-fold higher than standard long-period gratings in this range. The full width at half-maximum of the fabricated grating is only about 0.6 nm, allowing for high-resolution sensing. Moreover, the grating period is so small that the attenuation dip corresponding to a high-order Bragg resonance can also be seen, which can act as a monitor of the unwanted perturbation to realize dual-parameter sensing.
authors.forename: Fangcheng
authors.initials: F
authors.lastname: Shen
authors.forename: Changle
authors.initials: C
authors.lastname: Wang
authors.forename: Zhongyuan
authors.initials: Z
authors.lastname: Sun
authors.forename: Kaiming
authors.initials: K
authors.lastname: Zhou
authors.forename: Lin
authors.initials: L
authors.lastname: Zhang
authors.forename: Xuewen
authors.initials: X
authors.lastname: Shu