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...http://www.google.es/patents/US6876791?utm_source=gb-gplus-sharePatente US6876791 - Diffraction grating device
