Radiation Characterization of Optical Frequency Domain Reflectometry Fiber-Based Distributed Sensors

We studied the responses of fiber-based temperature and strain sensors related to optical frequency domain reflectometry (OFDR) and exposed to high
$\gamma $
-ray doses up to 10 MGy. Three different commercial fiber classes are used to investigate the evolution of OFDR parameters with dose, thermal treatment and fiber core/cladding composition. We find that the fiber coating is affected by both thermal and radiation treatments and this modification results in an evolution of the internal stress distribution inside the fiber that influences its temperature and strain Rayleigh coefficients. These two environmental parameters introduce a relative error up to 5% on temperature and strain measures. This uncertainty can be reduced down to 0.5% if a prethermal treatment at 80 °C and/or a preirradiation up to 3 MGy are performed before insertion of the fiber in the harsh environment of interest. These preliminary results demonstrate that OFDR fiber-based distributed sensors look as promising devices to be integrated in radiation environments with associated large ionizing doses.