Photowritten bragg grating apodization method

Abstract

The invention relates to an exposure method for producing a Bragg grating on a photosensitive guide ( ) or optical fiber ( ), in which method the guide (the fiber) ( ) is scanned by a light beam ( ) and means ( ) are provided for modulating the exposure time along the guide (the fiber) by varying the speed at which the beam ( ) moves along the guide (the fiber) ( ) so that it is located opposite each location of the guide (the fiber) ( ) for a time period that varies with the location, the method including the step of disposing in front of the guide (the fiber) ( ) a system ( ) adapted to create interference fringes on the guide (the fiber) ( ) and to scan the beam ( ) over the interference system ( ) at a speed that is modulated along the system ( ), and furthermore the step of having the beam scan the guide (the fiber) ( ) at a modulated speed without the interference system ( ) on the path of the beam ( ), the scanning with the interference system ( ) being effected with modulation of the exposure time increasing the exposure time in the central part of the guide (the fiber) ( ) and the scanning without the interference system being effected with modulation of the exposure time reducing the exposure time in the central part of the guide (the fiber) ( ).