Patent ID: 7593609

Claim:
A method for modulating refractive indices of optical fiber gratings comprising: providing an optical fiber grating having a plurality of assigned locations; providing a first UV (Ultra-Violet) beam and a second UV beam sequentially exposing said assigned locations section by section; and controlling intensities and phases of said first UV beam and said second UV beam for maintaining each said assigned location at a fixed value of a total exposure intensity exposed by said first UV beam and said second UV beam to modulate a refractive index of said optical fiber grating, wherein said first UV beam and said second UV beam respectively expose each said assigned location by an identical intensity; phase differences between each said assigned location and positions where said first UV beam and said second UV beam are projected on said optical fiber grating are respectively Δθ and −Δθ; refractive indices of said optical fiber grating are modulated via varying said phase differences Δθ and −Δθ.