Gold thickness dependence of SPR-based hetero-core structured optical fiber sensor

Sensing performances of surface plasmon resonance (SPR) hetero-core fiber sensor has been presented based on SPR excitation by controlling the thickness of gold metal coating ranging from 20 to 70 nm. Experimental results have demonstrated an attractive feature in their metal thickness dependences, showing the sensing capability in the uses both of the spectral and of the amplitude mode operations. Sensing resolutions have been achieved to be in the range of 7.40 × 10−4 to 3.64 × 10−5 RIU for 1.333–1.398 RIU range of tested glycerin solutions for the spectral operation with a spectral resolution of 0.5 nm, and in the range of 4.80 × 10−4 to 9.31 × 10−5 RIU for 1.333–1.384 RIU for the amplitude operation with a given wavelength of 667 nm. A practical sensing scheme has been successfully operated based on the amplitude mode using a single LED emitting 667 nm, showing the real time-based, remote sensing capability in measuring refractive indices of liquids.