High-sensitivity gas pressure sensor based on a multimode interferometer using hollow-core tube lattice fiber

A non-diaphragm fiber gas pressure sensor based on a multimode interferometer (MI) using a hollow-core tube lattice fiber (HC-TLF) as a gas cell is proposed and experimentally demonstrated. The sensor is fabricated by fusion splicing a sandwich structure of a graded-index multimode fiber, HC-TLF, and lead-in/out single mode fiber. Several side-holes are drilled by using a femtosecond laser on the side wall of the HC-TLF to allow gas in and out of the fiber. The positions of side-hole in HC-TLF have been investigated. during the experiments, which indicate that the highest gas pressure sensitivity existed as the side-hole located in the gap between adjacent cladding holes of the HC-TLF. The proposed structure exhibits a high sensitivity of 8.1 nm/MPa with the average gas fill time of 2.2 s. This sensor also has low temperature sensitivity and low temperature cross sensitivity of 12.3 pm/degrees C and 1.5 kPa/degrees C as the temperature rises to 400 degrees C. In addition, the advantages of the gas pressure sensor, such as small size, rapid response, low temperature cross sensitivity, and simple fabrication process, make it suitable for high-pressure measurement in harsh conditions, e.g., downhole and ocean bottom. (C) 2020 Optical Society of America