Dual Self-Growing Polymer Microtips on a Multicore Fiber for Humidity and Temperature Discriminative Sensing

We have proposed and fabricated dual self-growing polymer microtips, acting as parallel Fabry-Perot interferometers (FPIs), at the end-facet of a multicore fiber (MCF). With the significantly different responses of these two FPIs, a highly discriminative sensing of humidity and temperature has been demonstrated. The achieved condition number of 3.98 is the lowest in the reported discriminative fiber optic sensors for humidity and temperature, indicating the high reliability when implementing the discriminative measurement. In addition, the low relative-measurement errors of less than 0.49% for the humidity and 1.64% for the temperature have been experimentally verified. The two densely-integrated microtips, with the radial distance less than 40 μm, can notably improve the spatial measurement accuracy, and the signals of MCF-tip FPIs can be effectively collected by the fan-in and fan-out device. The proposed sensing microtips at the top of MCF provide a compact, flexible, and scalable scheme for sensitive discriminative measurements, which may pave the way towards micro-scale integrated fiber optic devices for multi-parameters sensing, and accelerate various MCF applications.