Versatile Interferometric Sensor Based on Sandwiched Grapefruit Photonic Crystal Fiber

An interferometric sensor based on grapefruit photonic crystal fiber (PCF) is proposed and demonstrated for several physical parameter sensing. The PCF is sandwiched between two single-mode fibers (SMFs) through a short multimode fiber (MMF) at its both ends to form a Mach-Zehnder interferometer (MZI) with a total length of less than 2 mm. Combined with femtosecond laser micromachining and selectively filling technique, the micro-channels in the PCF are flexibly used for highly sensitive strain, gas refractive index/pressure, and temperature measurements. Moreover, device can also be used for hydrogen sensing with a high sensitivity of ~3.00 nm/% (vol. %) by coating Pt-loaded WO3 on its lateral surface. Meanwhile, the unique signal demodulation technique based on inverse Fourier transform is adopted to extract out desired information. The proposed device has promising potential in many physical parameter sensing, environmental monitoring, and hydrogen energy measurement owing to its high sensitivity, versatile sensing capability, and compact size.