Effect of resin type on the signal integrity of an embedded perfluorinated polymer optical fiber

Abstract

Polymer optical fibers (POF) hold many advantages for embedded sensing, such as their low cost, flexibility, high tensile strain limits and high fracture toughness. POF sensors may therefore be integrated into fiber reinforced composite structures for monitoring structural behavior. Since POFs do not require a protective coating, it is critical to verify that the resin system does not have a negative impact on the noise level or performance of POF sensors during composite manufacture. This study measured the effect of vinylester and epoxy resin systems on the signal loss of embedded perfluorinated, graded index POFs. Photon-counting optical time domain reflectometry (OTDR) was used to monitor the signal attenuation and backscattering level of the POFs throughout the resin curing cycle. Fourier transform infrared spectrometry (FTIR) and cross section analyses using scanning electronic microscope (SEM) images were also conducted to investigate whether the resin system caused chemical and physical changes of the POF. This study showed that vinylester resin caused a significant increase in the backscattering level of POF sensors and therefore induced high fiber signal losses. On the other hand, the POF treated with epoxy showed no change in backscattering level, indicating that no chemical or physical change had occurred to the POF.