EFFECTS OF DRAWING TENSION ON THE PHOTOSENSITIVITY OF SN-GE-CODOPED AND B-GE-CODOPED CORE FIBERS

The influence of drawing tension on the formation of Bragg gratings in B-Ge- and Sn-Ge-codoped core fibers is investigated by transmission a nd stress measurements. With increasing drawing tension, the axial str ess is reduced in the B-Ge-codoped core but increased in the Sn-Ge-cod oped core. A higher drawing tension leads to a photosensitivity enhanc ement and an increase of the core stress during the grating formation in B-Ge-codoped fibers. For Sn-Ge-codoped fibers, increased drawing te nsion results in an UV-induced stress decrease accompanied by a reduct ion of the photosensitivity. The results are discussed on the basis of an UV-induced compaction of the core network. (C) 1998 Optical Societ y of America.