Abstract: Samples of D-shape fiber are fabricated using grinding fiber preform, and Bragg gratings are incurved into these samples. Practical aspects in fabrication and measurements are presented. By deep etching into the core, sensitivity of Bragg wavelength to the refractive index is increased. Changes in resonant wavelength of different modes of the D-shape few-mode fiber Bragg grating with respect to surrounding refractive index and temperature, respectively, are measured. The measured data well agree with simulation results, providing a good base for further research on the sensing surrounding refractive index.

Key words: Bragg grating, mode couple
, refractive index measurement, D-shape fiber