Singlemode hetero-core fiber based refractometer demodulated in a ratiometric system
We propose a fiber refractometer based on a singlemode-small core singlemode (SCSMF)-singlemode (SMF28-SCSMF-SMF28) structure demodulated by a ratiometric measurement system. Both the SMF28 and SCSMF fibers have a step index profile and the conventional SMF28 fiber is used at both ends as the attaching fiber to the small core SMF fiber. By measuring the power variations at the output of the refractometer, the surrounding refractive index (SRI) can be determined. Experiments demonstrate a maximum RI sensitivity of 1.55×10−5 in the SRI range from 1.3340 to 1.4485.