Experimental investigation of field distributions for chirped fiber Bragg grating

Chirped fiber Bragg gratings (CFBGs) are used in applications ranging from fiber optic communication, optical fiber sensing, to optical information processing, among which the field distributions are vital in improving their performance. Here, we investigate the optical field distributions of CFBGs based on the finite element method and experimentally verify the evanescent field distribution properties of a CFBG fabricated by ultraviolet exposure method based on an InGaAs linear image sensor. From the simulation, we can find that the reflective locations of the evanescent field and the internal field distributions move linearly along the fiber grating region as the incident wavelength increases. A slight difference that was found for the evanescent field was that the intensity for areas far away from the reflective region diminishes gradually. The obtained experimental data are fully consistent with that obtained from the simulation. The exploration of the field distributions of CFBGs is expected to provide more information for the subsequent analysis of fiber grating fields, the investigation of material refractive index modulation mechanism during grating fabrication, the fabrication of special fiber gratings, and so on.