Cascaded Fabry–Pérot Interferometers with Vernier Effect for Gas Pressure Measurement

A sensitivity enhanced gas pressure sensor with Vernier effect is proposed in this paper. The sensor is a cascade configuration which includes two Fabry-Pérot interferometers (FPIs) with different free spectrum range (FSR). Each Fabry-Pérot interferometer is fabricated by inserting a piece of hollow core fiber (HCF) in between two sections of single mode fiber (SMF). Femtosecond laser is applied for drilling an opening on the HCF of sensing FPI to make the air hole interact with outside environment, while the air hole of the reference FPI is kept closed. Gas pressure response is measured by monitoring the wavelength shift of the envelope extracted from the superimposed spectrum of the cascaded FPIs. Experimental results show that the sensitivity of the cascade configuration can attain -65.482nm/MPa, which is -13 times of single sensing FPI.