Induced loss of optical fibers exposed to nuclear reactor thermal neutrons

The base material currently used for optical fiber waveguides (optical fibers) is silica. By adding various impurities, properties required for optical transmissions are created. When these optical fibers are used in a particular environment, such as a nuclear reactor, damage caused by radiation from the source becomes a serious problem. It is well-established that when optical fibers are exposed to 60 Co γ-rays, the attenuation of the signal through the fiber decreases (1–3). This is due to damage produced in the fiber by radiation. The nuclear reactor radiates not only γ-rays, but also thermal neutrons. However, the effect of the thermal neutron on optical fibers has not been established.