Accurate characterization of fiber Bragg grating index modulation by side-diffraction technique

The performance of fiber Bragg grating (FBG) devices is determined by spatial distribution of FBG parameters. For many applications, like chirped FBG used for dispersion compensation, it is sufficient to control these parameters with spatial resolution of around 1 mm. We improve the sensitivity and accuracy of the side-diffraction FBG characterization at the cost of reducing the spatial resolution and demonstrate simultaneous measurement of fiber grating refractive index modulation with accuracy of 2/spl middot/10/sup -6/, grating period variation with accuracy of 5 pm, and spatial resolution of /spl sim/1 mm. The group delay ripple of a chirped FBG calculated from our side-diffraction characterization is in a good agreement with spectroscopic measurements.