Patent ID: 6973237
Filing Date: 2005-12-06
Classification: G02B

Abstract:
1. A method of producing an optical-fiber grating, comprising the steps of: fixing a relative position between an optical fiber and a phase mask formed with gratings, to a first position; forming an interference light of predetermined grating width through the phase mask by an ultraviolet beam from a laser, at the first position, and irradiating the optical fiber with the interference light in one portion or in a plurality of portions at a predetermined grating spacing, thereby to form one or more first optical-fiber gratings; moving the phase mask and/or the optical fiber in a lengthwise direction of the optical fiber, and fixing the relative position between the phase mask and the optical fiber, to a second position; forming an interference light of predetermined grating width through the phase mask by the ultraviolet beam from the laser, at the second position, and irradiating the optical fiber with the interference light in one portion or in a plurality of portions at the predetermined grating spacing, thereby to form one or more second optical-fiber gratings; and irradiating the optical fiber with the ultraviolet beam from the laser without intervention of a phase mask, in an interspace between the first optical-fiber grating and the second optical-fiber grating in order to adjust a phase shift, thereby to form a phase shifting region, wherein, in a case where a total length or a channel spacing of a super structure optical-fiber grating is to be made 1/m (m=2, 3 . . . ), a phase shift φ (where 0≦k≦N FBG holds, N FBG indicates the number of the optical-fiber gratings, and φ k is turned back at 2π).