Study on fabrication, spectrum and torsion sensing characteristics of microtapered long-period fiber gratings

摘要

Based on the photoelastic effect, a microtapered long-period fiber grating (MLPFG) is fabricated by using a CO2 fusion splicer, which has high repeatability and small loss. By analyzing the spectrum of the grating, it is easy to know that the grating has a significant absorption effect only for light with a specific wavelength (such as lambda approximate to 1569 nm). In the process of fabrication, it is found that with the increase of refractive index modulation, the extinction ratio of the spectrum increases gradually, and the resonant dip drifts toward the long wavelength. In addition, it is found that the twist direction and the torsion angle of the grating can be judged by observing the change of the spectrum in the experiment of exploring the sensing of torsion. When the grating is twisted clockwise, wavelength and extinction ratio of the resonant dip decrease gradually; when the grating is twisted counterclockwise, the wavelength increases gradually, but the extinction ratio increases first and then decreases. The torsion sensitivity is 0.10 nm.mm.rad(-1), which is about two times higher than that of CLPGs fabricated from photonic crystal fibers and about three times higher than that of conventional LPFGs. By utilizing these characteristics of MLPFG, it can be widely used in filters and sensors.