Gamma Induced Transparency Loss of Thick Quartz Fibres

Radiation response of thick multi-mode Ge, P, F -doped quartz fibre has been examined after exposure to 60^Co gamma-source within a dose interval of 10 - 10^7 Gy at a dose power of 2.3 and 24 Gy/s at 300K. The induced transparency losses A at the wave length of 1.06 mkm do not exceed 0.2 after a dose of 10^6 Gy and reach a saturation, while the fibres are closed for visible light after a smaller dose. Varying focus and an angle of leading a probe light beam in fibre, the core modes were found to close at a dose of 10^4 Gy due to radiation induced colour centres of Ge and non-bridging oxygen O, and the clad modes were suppressed at 500 Gy by the expense of Al impurity colour centres.