Influence of fiber drawing tension on photosensitivity in hydrogenated and nonhydrogenated fibers

Summary form only given. One point not yet studied on the way of optimization of fiber Bragg grating (FBG) elaboration is the effect of fiber drawing tension /spl tau/. It is established that two types of grating can be distinguished in a non-hydrogen-loaded (H/sub 2/) high germanium content fiber: type I grating, growing first, having a positive index change, and type IIa grating with a negative one. In H/sub 2/ loaded fibers, only type I is detected. The influence of a tensile stress applied to the fiber during irradiation has been previously studied at 244 nm. It has been shown that the maximum index modulation amplitude for type I grating and for grating in H/sub 2/-loaded Ge-fiber decreases under fiber stretching, while the growth of type IIa grating is accelerated. We also know that the increase of the fiber drawing tension /spl tau/ reduces the fiber core stress, but it is not the only effect, the defect population is changed also. Thus, in this work we investigate the drawing tension effect in order to optimize type I photosensitivity at 244 nm in hydrogenated or not fibers as it was performed with 193-nm laser.