A proposal of T-structure fiber-optic refractive index sensor based on surface plasmon resonance

We present a compact and novel “T” structure optical fiber refractive index sensor proposal based on surface plasmon resonance. “T” structure sensing head consists of a single mode fiber (SMF) with a plasmonic facet and a cladding partly removed single mode fiber (CPR-SMF) with a gap. The gold film is deposited on the end of SMF instead of the side of the CPR-SMF. The simulation results show that the SPR based on the “T” structure can be excited effectively. The SPR transmission spectrum shifts towards longer wavelength with the sensing sample refractive index increasing largely. When we divide the refractive index range of the sensing sample to two parts, the linear relationships between the SPR wavelength and the refractive index can be used. The resolutions can be highly up to 7.115×10−6 RIU and 3.525×10−6 RIU for the refractive index ranges of 1.3333-1.36 and 1.37-1.4, respectively. The proposed “T” structure sensor works well for achieving the refractive index measurement with high sensitivity and wide range for samples with a tiny amount.