Distributed multi-parameter sensor based on Brillouin scattering in an etched few-mode multi-core fiber

Abstract

We theoretically propose a unique distributed multi-parameter sensor based on an etched few-mode multi-core fiber (FM-MCF) for simultaneous sensing of temperature, strain, and sample refractive index (SRI). These three parameters can be sensed simultaneously by combining space division multiplexing (SDM) and stimulated Brillouin scattering (SBS). FM-MCF naturally contains an inner core and an outer core, and it is etched until the outer core is exposed. Therefore, the inner core can be employed to calculate the Brillouin gain spectrum (BGS) of LP01 and LP11 through distributed temperature and strain, and the outer core can be used to sense SRI through the BGS of LP01. Note that due to the high corrosion of the outer core, the higher order mode is cut off, so only the LP01 mode can be observed in the outer core. By demodulating the Brillouin frequency shift (BFS) of the BGS in the outer core and the inner core, the proposed sensor has a maximum temperature sensitivity of 1.7220 MHz/°C, a maximum strain sensitivity of 0.0783 MHz/με, and an SRI sensitivity of 274.3245 MHz/RIU around 1.440 RI unit (RIU). Therefore, we show a new perspective for discriminative sensing of multi-parameter in Brillouin distributed sensors based on SDM. The developed multifunctional fiber sensor could find application in the field of environmental sensing, materials science, biomedical applications, and structural health monitoring.