Sensitive enhanced refractive index sensor based on series tapered thin-core microfiber with Vernier effect

We reported a refractive index (RI) optical fiber sensor using series tapered thin-core microfiber (TTCMF) based on the optical Vernier effect. In the RI measurement range from 1.3313 to 1.3392, an ultra-high RI sensitivity of - 15,053.411 nm/RIU was obtained by using the series structure, which was about 4.65 times higher than that of the single TTCMF one. Based on the advantages of high RI sensitivity and simple structure, the proposed sensors have great potential in the biosensing fields.