Reflective Tilted Fiber Bragg Grating Refractometer by Interacting with Multimode Fiber

A simple refractive-index fiber sensor based on a tilted Bragg fiber grating interacting with multimode fiber is described. The sensor structure is formed by insertion of a small section of MMF between the single-mode fiber and the tilted Bragg fiber grating. The average reflective power in the cladding modes of the TFBG reflected a different power as the surrounding refractive index changes, while the power of the reflected Bragg mode keeps unchanged. The refractive index unit sensitivity of 28.5 μW is achieved. The proposed sensor shows great potential for biological applications.