All in-fiber Fabry–Pérot interferometer sensor towards refractive index and temperature simultaneous sensing

The majority of biology and chemistry takes place in solution, in which refractive index (RI) and temperature sensing underlie molecular detection and profiling. All-in-fiber integrated devices are uniquely suited to detecting the properties of samples, which allows liquids to flow and react in the fiber cavities. Here we use a single-hole dual-core fiber (SHDCF) based Fabry–Pérot interferometer (FPI) to simultaneously detect the refractive index and temperature of solution, with high sensitivity enhanced by the vernier effect. The inlets and outlets are built by splicing C-shaped fiber and fiber capillary between SHDCF. A detection region inside the microscopic hole of SHDCF obtained after splicing is constructed. Our method offers high sensitivities of 6851.89 nm/RIU and 0.493 nm/℃ for RI and temperature in a liquid solution, respectively. Notably, the cross-sensitivity of RI and temperature can be eliminated by constructing a transmission matrix. New in-fiber integrated ways of revealing properties of low-volume samples may have extensive potential for applications in the biological and chemical sciences.