Monitoring surface crystal growth using an intrinsic exposed-core optical fiber sensor (IECOFS)

Abstract

An unclad section of silica optical fiber has been used to detect, and measure heterogeneous (surface) crystal growth in a solution of calcium carbonate. Surface crystal growth is found to attenuate radiation transmitted along the fiber core via the refraction of guided modes out of the core. Optical power output was found to be linearly correlated with crystal size (R² = 0.97, n = 9) and the optical signal was found to be restored following chemical removal of deposited crystals (without physical intervention). Sensitivity to crystal growth was found to be proportional to the length of the unclad (exposed) core and inversely-proportional to fiber diameter. These results suggest a simple skip-length ray model, coupled with refraction of guided modes out of the fiber core can be invoked to explain the mechanism of optical power attenuation.