Evanescent wave on the gold-coating tilt fiber grating surface and its sensing applications

The scatterings of P and S-polarized evanescent wave on the surface of a tilted fiber Bragg grating (TFBG) with a 50 nm thick gold coating were investigated experimentally by observing radiation patterns from discontinuities in the coating. The scattering intensity for P-polarized light is larger than for S-polarized light when the evanescent wave propagates from the coating towards the discontinuity. Using the characteristics of the polarization of the evanescent wave, the in-line polarimeter and twist sensors were designed.