Abstract
Optical fiber sensors (OFS) are a potential candidate for monitoring physical parameters in nuclear environments. However, under an irradiation field the optical response of the OFS is modified via three primary mechanisms: (i) radiation-induced attenuation (RIA), (ii) radiation-induced emission (RIE), and (iii) radiation-induced compaction (RIC). For resonance-based sensors, RIC plays a significant role in modifying their performance characteristics. In this paper, we numerically investigate independently the effects of RIC and RIA on three types of OFS widely considered for radiation environments: fiber Bragg grating (FBG), long-period grating (LPG), and Fabry-Perot (F-P) sensors. In our RIC modeling, experimentally calculated refractive index (RI) changes due to low-dose radiation are extrapolated using a power law to calculate density changes at high doses. The changes in RI and length are subsequently calculated using the Lorentz–Lorenz relation and an established empirical equation, respectively. The effects of both the change in the RI and length contraction on OFS are modeled for both low and high doses using FIMMWAVE, a commercially available vectorial mode solver. An in-depth understanding of how radiation affects OFS may reveal various potential OFS applications in several types of radiation environments, such as nuclear reactors or in space.
Highlights
Andrei Stancalie and Flavio EspositoNuclear power is a potential clean energy solution to the world’s ever-increasing energy demands [1,2]
Work has shown that three types of resonance-based optical fiber sensors (OFS)—fiber Bragg grating (FBG), long-period grating (LPG), and Fabry-Perot (F-P)—have been widely tested in nuclear environments [8,9,10,11,12,13,14,15]
To numerically investigate how radiation affects optical performance, we modeled solve a large variety of waveguides made of almost any material and any geome three types of resonance-based sensors (FBG, LPG, and F-P) using a robust and fully vecsupports a rich number of complementary algorithms
Summary
Nuclear power is a potential clean energy solution to the world’s ever-increasing energy demands [1,2]. RIA reduces the amplitude of the spectral response and is caused by radiation-induced defects in silica material, resulting in modification of the fiber absorption band. These defects are primarily a function of fiber composition, and a significant amount of work has been performed to mitigate such defects, including studying fiber composition and irradiation conditions, choosing an appropriate wavelength of light, and optimizing manufacturing conditions. Based on the radiation-induced RI values in [18], we used the Lorentz–Lorenz relation to calculate the corresponding density and length change in the optical fiber and studied its effects on sensor response. Discusses the effects of RIA up on the these three types of sensors; and Section 6 offers concluding
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