Damage of Optical Fibers Under Wet Environments

Abstract

International audienceBesides signal transmission for telecommunications, fibers are used in an increasing number of devices. A number of applications relate to devices exposed to severe wet environment (hot water, chemical attacks...). It is the case for the sensors used in nuclear plants, high energy physics or plasmas devices. However, reliability issues must be addressed for optical fiber sensors operating under severe conditions such as harsh chemical solutions. The purpose of this work is to study the mechanical behavior and aging of fibers exposed to hot water action, to hydrofluoric acid vapours (HF) and to tetramethoxysilane (TMOS) for different durations. Dynamic fatigue tests were implemented using a two-point bending testing device or tensile test set-up. Standard fibers tested immediately after exposure show a broader distribution of fiber strength accompanied by the drastic decrease of the failure stress. In some particular cases, the gain compared to as received fibers can be positive. Polymer reacts with different wet environments, which induces viscosity changes. This is consistent with SEM observations

Mechanical Properties of Optical Fibers

“…The application of optical fiber in aggressive environments may lead to the degradation of its physic reliability and therefore the performance of the systems in which it is applied (El Abdi et al, 2010). Therefore, the conservation of the optical fiber physical characteristics in harsh environments, where the fiber is exposed to abrasion and moisture, is a key point to assure its good performance.…”

“…Nevertheless, and in spite of the protection provided by the coatings, the fiber is still permeable to moisture. There are reports of its ability to retain the hydroxyl groups from the water molecules, (Berger et al, 2003;Méndez et al, 2007;El Abdi et al, 2010;André et al, 2011), but also of the diffusion of other ions in addition to the ones from water. Such ions diffusion can be responsible for the optical fiber degradation and the decrease of its strength (Thirtha et al, 2002;Lindholm et al, 2004).…”

“…For an optical fiber α'=6 (El Abdi et al, 2010). By applying equation (4) to the measured data, we can determinate the applied stress at which the fiber fractures.…”

Optical fibres coating aging induced by the maritime environment

“…It is long known from literature [3] [4], that for fibers subjected to harsh environments for long periods, the fiber strength drastically drops after a certain time, corresponding to a fatigue transition,…”

“…The non linear elastic parameter, α, is given by: For an optical fiber α'=6 [3]. By applying equation (1) to the measured data, we can determinate the applied stress at which the fiber fractures.…”