PHOTOCONDUCTIVITY MEASUREMENTS IN OPTICAL-FIBER PREFORMS

The AC photoconductivity and the photodielectric shift in UV-illuminated germano-silicate preforms and optical fibres has been measured using a noncontact microwave resonator technique at 2.9 GHz. The highest photoconductivity measured was 1.5 x 10(-6)(OMEGA cm)-1 and the largest measured photodielectric shift corresponded to an increase of the refractive index of 1.6 x 10(-2). A permaNently induced increase of the refractive index, 6.1 x 10(-3), was also observed. The dark DC conductivity was measured to be 10(-15)(OMEGA cm)-1.