Ultra-sensitive gas pressure and temperature sensor based on self-forming film technique and vernier effect

In this paper, an ultra-sensitive gas pressure and temperature sensor based on vernier effect is presented. It consists of a single mode fiber (SMF) and hollow cylindrical waveguides (HCW). Through the self-forming film technique, a gelatin film is manufactured at the air core of HCW, and the thickness of the gelatin film manufactured by this technique is only 3.16 μm. The vernier spectrum is formed by the superposition of the spectra of the air cavity (AC) and the mixing cavity. The mixing cavity is composed of AC and gelatin cavity (GC). The thin gelatin film makes the optical path difference between the AC and the mixing cavity smaller, which is beneficial to increase the vernier magnification factor. When the gas pressure changes, the gelatin film will deform abnormally. This abnormally deformation squeezes the film, causing the cavity length of the air cavity to become longer. The experimental results show that the sensor exhibits a high gas pressure sensitivity of 788.22 nm/MPa, and the temperature sensitivity is 0.39 nm/℃. The proposed sensor enables simultaneous measurement of gas pressure and temperature. It also processes the advantages of compact size, low cost, and strong mechanical strength, which makes it suitable for aerospace, Biomedical and Natural gas detection.