Radiation sensitivity of plastic optical fibres

Plastic optical fibres were improved considerably during the last few years. It was investigated whether polymethyl methacrylate (PMMA) and polycarbonate (PC) fibres would also be suited for radiation environments. The fibres were irradiated with 60Co gamma rays. Varied test parameters were the light wavelength (670 nm, 780 nm), the light power (0.1 10E-6 W, 20 10E-6 W, approx. 750 10E-6 W), the fibre temperature (-40 degree C, +80 degree C), the radiation dose rate, and the surrounding atmosphere (normal air, dry nitrogen, increased humidity, vacuum). It was found that PMMA fibres can be used up to total dose values of about 10E15 rad. The radiation-induced loss of the PC fibre surpasses their intrinsic attenuation at dose values greater approx. 10E4 rad. A dry nitrogen atmosphere as well as vacuum increases the radiation sensitivity of PMMA fibres seriously.