Diffraction grating device

摘要

In a diffraction grating device (1), index modulations are formed along the longitudinal direction of an optical fiber (10) serving as an optical waveguide. The optical fiber (10) has a core region (11), an inner cladding region (12), and an outer cladding region (13) sequentially from the optical axis center. Index modulations are formed in both the core region (11) and the inner cladding region (12) of the optical fiber (10) in each of a plurality of regions A1 to AN (N is an integer; N>=2) separated from each other along the longitudinal direction of the optical fiber (10). In the diffraction grating device (1), regions An (n=1 to N) in which index modulations are formed in both the core region (11) and the inner cladding region (12) and regions Bn (n=1 to N-1) in which no index modulations are formed alternately exist along the longitudinal direction.