Vulnerability of OFDR-based distributed sensors to high γ-ray doses

Abstract

Vulnerability of Optical Frequency Domain Reflectometry (OFDR) based sensors to high γ-ray doses (up to 10 MGy) is evaluated with a specific issue of a radiation-hardened temperature and strain monitoring system for nuclear industry. For this, we characterize the main radiation effects that are expected to degrade the sensor performances in such applicative domain: the radiation-induced attenuation (RIA), the possible evolution with the dose of the Rayleigh scattering phenomenon as well as its dependence on temperature and strain. This preliminary investigation is done after the irradiation and for five different optical fiber types covering the range from radiation-hardened fibers to highly radiation sensitive ones. Our results show that at these high dose levels the scattering mechanism at the basis of the used technique for the monitoring is unaffected (changes below 5%), authorizing acceptable precision on the temperature or strain measurements. RIA has to be considered as it limits the sensing range. From our vulnerability study, the OFDR sensors appear as promising candidates for nuclear industry even at doses as high as 10 MGy.

Investigation of Coating Impact on OFDR Optical Remote Fiber-Based Sensors Performances for Their Integration in High Temperature and Radiation Environments

“…The most important being radiation induced attenuation (RIA) that affects light propagation along the fiber length. As discussed in [7] and [8], for OFDR-based distributed sensors, RIA has a strong impact on the maximum sensing length. To evaluate the response of our samples, we estimated permanent RIA by linear attenuation measurements in the irradiated samples.…”

“…Our recent studies have investigated the vulnerability of Optical Frequency Domain Reflectometry (OFDR) fiber sensor to ionizing radiation [7] [8]. The study in [7] deals with the permanent γ-radiation effects up to 10 MGy on five different fibers classes, from radiation resistant to radiation sensitive ones.…”

“…The study in [7] deals with the permanent γ-radiation effects up to 10 MGy on five different fibers classes, from radiation resistant to radiation sensitive ones. It is shown that the scattering mechanism at the basis of OFDR technique for the monitoring of temperature and strain is unaffected (changes within 5%), thus authorizing good precision on the distributed measurements.…”

Steady γ-Ray Effects on the Performance of PPP-BOTDA and TW-COTDR Fiber Sensing

“…For the sensors exploiting the silica structure signature, it is also mandatory to consider the possible radiation-induced refractive-index changes that could originate from several origins: radiation-induced point defects and densification. Several sensor classes have already been recently tested under irradiation, such as those exploiting the fiber Brillouin [5,6,7,8,9], Rayleigh [3,10] and Raman [2] scattering signatures of silica-based fibers. Whereas the Raman technology detects only the temperature, the Brillouin and Rayleigh scatterings are sensitive to both the applied strain and the temperature.…”

“…To the best of our knowledge, the on-line performances (during irradiation) of both the PPP-BOTDA and TW-COTDR sensing technologies are not yet documented in the literature. The γ-radiation effects on Brillouin responses were studied with BOTDA in [6], while the γ-radiation effects on Rayleigh were studied with OFDR technology in [10]. These BOTDA and OFDR technologies differ in terms of architectures from the ones discussed here, and the complex basic mechanisms of radiation effects on silica-based optical fibers can differently alter their sensing performances.…”