Fiber liquid-pressure sensor with high sensitivity and a wide measurement range using photopolymer

This paper presents a novel fiber liquid-pressure sensor that uses photopolymer glue to generate Fabry–Perot (F-P) interference, resulting in high sensitivity and a wide measurement range. The sensor comprises a single-mode fiber and photopolymer glue; the latter adheres to the fiber’s end face and is decomposed by a 405-nm laser to create an air channel with a diameter of 5.9 µm and a length of 50 µm. When the air channel is placed underwater, a 17.5-µm air cavity forms between the fiber core and the air–liquid boundary due to the pressure balance, creating an F-P interferometer. Based on experimental results, the sensor has an average pressure sensitivity of 5.68 nm/kPa over 0.49–2.94 kPa. The sensitivity can be maintained at this level across different pressure measurement ranges (up to about 500 kPa) by using a 980-nm laser’s radiation pressure to reset the air–liquid boundary. Besides its high sensitivity and wide measurement range, the sensor’s straightforward structure, durability, affordability, compactness, and simple construction make it an appealing choice for liquid pressure measurement applications in various fields.