Experimental investigation of a boron-codoped germanosilicate preform based on the color-center model

In this paper we studied the UV-induced refractive index changes of a boron-codoped germanosilicate preform used for the fabrication of fiber gratings. Two groups of preforms, non-H/sub 2/ loaded preform and H/sub 2/ loaded preform, have been exposed to a UV beam at various pulse energy densities and pulse numbers, and their UV-induced excess losses have been measured. The corresponding refractive-index changes have been determined through a Kramers-Kronig analysis. Also, our experimental results were discussed and analyzed according to the color-center model of photosensitivity, and then some important conclusions were obtained by us.