PHOTODEGRADATION AND NONLINEAR EFFECTS IN OPTICAL FIBERS INDUCED BY PULSED UV-LASER RADIATION

Photodegradation of fused silica optical fibers was investigated durin g irradiation with pulsed uv-light for different laser parameters and coupling conditions. Colour center formation was detected by measuring absorption and fluorescence spectra between two subsequent laser puls es, E'- and NBOH-centers were detected after irradiation with 266 nm l aser pulses, with the result of higher absorption of laser light by NB OH-centers. In addition, stronger degradation with distinct repetition rate dependence was observed when the core-cladding interface region had been irradiated. This effect results in a dramatic decrease in tra nsmission and has to be avoided for optimum transmission by proper cho ice of coupling conditions. Nonlinear absorption and stimulated Raman- scattering were measured and their influence on uv-transmission for se nsor applications was determined.