Discriminating twisting direction by polarization maintaining fiber bragg grating

The twisting vector measurement is realized using a fiber Bragg grating (FBG) inscribed in a polarization maintaining fiber with a rotated splicing joint. The rotated splicing joint introduces an asymmetric structure in the polarization maintaining FBG (PMFBG) which leads to a unique spectral response for the clockwise and anticlockwise twist of the PMFBG. The opposite intensity change of the intersection region between the two principal Bragg reflections for the clockwise and anticlockwise twist is used to discriminate the twisting direction. The proposed PMFBGs have potential applications in multi-parameter sensing, e.g., temperature, strain, and twist.