Virtual Vernier effect-based high sensitivity optical fiber humidity sensor

This paper presents an optical fiber-based humidity sensor which has tunable sensitivity by using virtual Vernier effect. It is formed by splicing a short length of hollow core fiber (HCF) at the end of a single-mode fiber (SMF) and fabricating a membrane of Polyvinyl Alcohol (PVA)/Polyacrylic Acid (PAA) at the end of HCF for humidity sensing. The experimental data of the proposed sensor shows that the sensitivity of −140 pm/%RH is achieved. Then the virtual Vernier effect is applied for data processing of the humidity sensor and the sensitivity is amplified with an adjustable amplification factor up to 20. The maximum achieved sensitivity is −2.875 nm/%RH.