FILTER WAVE OPTICAL FIBER HAVING CHANGED PHOTOSENSITIVE PROFILE

摘要

PROBLEM TO BE SOLVED: To reverse the photosensitive profile of a core and a clad and to remove a filter wave rebound by doping a fiber by a photosensitive material changeable in its refractive index in such a manner that the inner portion of the fiber has the photosensitive rate lower than the photosensitive rate of its outer part. SOLUTION: The core 5 and clad 3 of the fiber is doped with a photosensitive dopant (germanium) which is changeable in the retractive index. The germanium is irradiated with laser beams 7 and 8 over the length corresponding to a filter wave section 6, by which a refractive index changing grating is obtd. In exposure, interference fringes 16 spread not only into the core 5 but into the clad 3 as well. The core 5 which is the inner portion of the fiber has the photosensitive rate (germanium concn.) smaller than the photosensitive rate of the layer on the inner side of the clad 3 which is the outer portion. Then, the photosensitive profile is reversed.