REDUCING INSERTION LOSSES OF A WRITTEN IN GRATING WITH MODE COUPLING IN THE CLADDING

摘要

The invention concerns an optical fibre having a core, a cladding and a grating written in by irradiation coupling at least a light mode in the cladding so that it is dissipated therein. The invention aims at gradually varying the mean index along the grating, at least at the ends of the grating. The gradual variation of the mean index, or of the index modulating amplitude for writing in he grating enables to limit insertion losses of the filter formed by the grating. By analogy, the invention ensures for a written in grating the equivalent of a gradual variation of the fibre core for connecting two optical fibres having different core diameters. The invention is particularly applicable to equalizing filters for wavelength multiplexing transmission systems.