Tilted Fiber Bragg Grating in Graded-Index Multimode Fiber and Its Sensing Characteristics

Tilted fiber Bragg grating （TFBG） and reflective tilted fiber Bragg grating （R-TFBG） were proposed and demonstrated in the graded-index multimode fiber （GI-MMF）. The TFBGs with grating planes tilted at an angle of 2.5° corresponding to the fiber axis were inscribed. The TFBGs in the GI-MMF had the good linear sensitivity to the temperature, strain and curvature. The fiber was then cleaved at the far end of the TFBG to form an R-TFBG using the Fresnel reflection of the fiber end. The reflective spectra of the R-TFBG were given, and the temperature sensing properties were also investigated.