Mechanical degradation of optical fibers induced by UV light

The mechanical resistance of UV irradiated optical fibers has been investigated by dynamic fatigue tests. The intrinsic Weibull distribution of the pristine and chemically stripped fiber were almost identical. The high germanium doped fiber was homogeneously irradiated using a KrF Excimer with different pulse energy densities and different total doses, both corresponding to typical Bragg grating fabrication conditions. The Weibull distribution of the irradiated fibers depends on the pulse energy density and the total irradiation dose. Both, a strong broadening and a reduction of the fiber strength were observed. With increasing total irradiation dose, the median breaking stress of the fiber decreases from 4.8 GPa for the pristine fiber to 2.5, 2.2, and 1.8 GPa for pulse energy densities of 50, 100 and 200 mJ/cm(2), respectively, for a total dose of 1 kJ/cm(2). At higher total irradiation levels (above 1.5 kJ/cm(2)) the median breaking stress and hence the strain were found to be independent of laser fluence with a value of 2.7 GPa for 200 mJ/cm(2).