Patent ID: 7382951

Claim:
A method for fabricating a complex fiber Bragg grating by using UV sequential writing, characterized by probing another reference grating as a phase reference for each grating section writing, comprising the steps of: (1) arranging a reference fiber Bragg grating and a waiting to be exposed optical fiber in parallel, the modulated amount of refractive index of the reference fiber Bragg grating is large and uniform; (2) allowing a probe beam to be incident along the Bragg angle of the reference grating to form a first-order Bragg diffraction beam when the positioning point of each UV beam overlap exposures is determined, and generating an interference fringe by causing an interference between the first-order Bragg diffraction beam and another reference beam; (3) after a translation stage ( 05 ) is shifted by a predetermined distance to around next positioning point, fine tuning the translation stage ( 05 ) to the final position of this positioning point by comparing the phase distributions of interference fringes before and after shifting the translation stage ( 05 ) by using a feedback system until phase distribution falls within a given error range; (4) turning on a UV beam exposure shutter for a given exposure time and then turning off the shutter; and (5) shifting the translation stage ( 05 ) to next positioning point, and repeating steps (3) and (4).