Evaluation of Distributed OFDR-Based Sensing Performance in Mixed Neutron/Gamma Radiation Environments

We report the study of a radiation resistant single mode optical fiber doped with fluorine exposed to mixed neutron and gamma-radiation up to 10(17) n/cm(2) fluence and >2 MGy dose to evaluate its performances when used as the sensing element of a distributed Optical Frequency Domain Reflectometry (OFDR). The use of complementary spectroscopic techniques highlights some differences between the responses of solely gamma-radiation (10 MGy) or mixed neutron and. (10(17) n/cm2 + >2 MGy) irradiated samples. Those differences are linked to the defect generation rather than to structural changes of the a-SiO2 host matrix. We show that a modification of the refractive index of similar to 10(-5) is induced at the highest investigated neutron fluence. However, the feasibility of distributed temperature measurements along the irradiated fiber is demonstrated with an accuracy of 0.1 degrees C over a sensing length up to similar to 130 m with the tested OBR4600 interrogator. These results are very promising for the integration of OFDR sensors in mixed neutron and gamma radiation environments.