Photosensitive optical guide for optical filter, has refractive index and photosensitivity profiles such that coupling of fundamental and cladding modes and its derivative are equal to zero, for given Bragg grating writing angle

摘要

The optical guide is adapted for receiving slanted Bragg grating (SBG) writing, the grating having a given angle 'theta'. The guide has a refractive index profile defining a core and a cladding and a photosensitivity profile such that coupling of the fundamental mode and the 'cladding mode' in the guide (K(theta )) and its derivative (K'(theta )) at an angle theta are equal to zero for the given angle (theta) of SBG writing. The photosensitivity profile has a step whose radial distribution is independent of step index between the core and cladding. An independent claim is also included for an optical transmission system having a gain equalizing filter comprising optical filters.