Photonic crystal fiber Fabry–Perot interferometer for humidity sensor

This work designed and implemented of photonic crystal fiber Fabry–Perot interferometer based on (SPR) technology for sensing the humidity of the environment. The FPI was created by directly splicing a short length of PCF (4 cm) solid core on one side with traditional multimode fiber (MMF) and depositing a nano-film of gold with a thickness of 40 nm on the end of the PCF sensor. The PCF–SPR experiment was observed for different degrees of relative humidity. The location of the resonant wavelength peaks is seen to change to longer wavelengths (redshift) as (the RH) increases due to the transmission of maximum energy from the reflected power of the light guided via the fiber to the surface plasmons. The calculated sensitivity, signal-to-noise ratio, figures of merit, and resolution are approaching; the S is 1.25 nm/%RH, SNR is 0.0066, the resolution is 0.08, and the FOM is 0.00083 for photonic crystal fiber.