Hybrid Vernier effect: sensitivity amplification and two-parameter measurement in cascaded Fabry-Perot interferometer fiber sensor.

Vernier effect enhances the sensitivity for interferometric fiber sensor, but indiscriminately amplifies cross-sensitivity to environmental parameters. Here, hybrid Vernier effect, a new theory based on the cascaded FPI, is proposed and demonstrated for cross-sensitivity elimination under the premise of sensitivity amplification. It combines traditional and high-order harmonic Vernier effects to measure two parameters simultaneously. The proposed sensor achieves strain sensitivity of 960.1 pm/µɛ, and temperature sensitivity of 1260.86 pm/°C. Stability experiments demonstrate excellent stability of envelope demodulation method, with minimum temperature resolution of 0.44 °C and minimum strain resolution of 0.58 µɛ. The proposed the hybrid Vernier effect can be achieved widely in common cascaded fiber FPI fiber sensor structure, making it good candidate for practical applications.