The radiation effect of gamma rays on optical fibers is introduced. The experiments of measuring the induced loss of optical fibers by steady-state and transient gamma rays are carried out. The electron density, collision frequency and plasma oscillation frequency of optical fibers under high dose rate pulsed gamma radiation are calculated. A transient radiation-induced loss model based on low temperature plasma absorption is proposed. The transient radiation-induced loss of optical fibers at 600-1600 nm is calculated and measured. The results show that: (1) At the wavelength of 1310 and 1550 nm, the results calculated on plasma absorption method and measured results of transient radiation-induced loss of optical fibers are in the same order of magnitude, and the experimental results verify the applicability of the plasma absorption model; (2) Plasma absorption and atomic defect absorption coexist when pulsed gamma rays act on optical fibers. The transient radiation-induced loss of optical fibers is the result of the interaction of two mechanisms; (3) In the range of 600-1600 nm, with the increase of detection wavelength, the radiation-induced loss of optical fibers is dominated by plasma absorption.
The general effect mechanism of pulsed gamma-ray on optical fibers is introduced. In order to measure pulsed gammaray radiation-induced loss, a transient experimental measurement system is developed. It employs pulsed diode lasers with five wavelengths as detecting carriers and high dose rate electron accelerator as irradiation source. The radiationinduced loss of pulsed gamma-ray on conventional single mode and multi-mode optical fibers are measured respectively. The experiment of two rare-earth-doped fibers spontaneous emission spectrum measurement system is established and the results of Er-doped and Yb-doped fibers are obtained also. Experimental results show that: (1) Radiation-induced loss is relevant to the fiber types. On the same experimental condition of pulsed gamma-ray radiation, the radiationinduced loss of multimode fibers is larger than single-mode fibers. (2) Radiation-induced loss will increase as the laser detecting wavelength shifts from near-infrared to visible regions of optical spectrum. (3) As the total dose increases, the spontaneous emission spectrum of the doped fibers decreases greatly, and the performance of the doped fiber will fail at a certain total dose.