Performance and analysis of pressure sensor with π-FBG on thick-walled cylinder for ultra-high oceanic pressure measurement

Abstract

Accurate pressure measurements in deep-sea environments require ultra-high-pressure sensors that maintain high precision across a wide range of temperatures and pressures. This paper presents the design and performance analysis of an ultra-high-pressure sensor based on a thick-walled cylindrical π-phase-shifted fiber Bragg grating (π-FBG). The sensor consists of a π-FBG element, a pressure conversion unit, and a robust encapsulation structure. It operates efficiently within a pressure range of 2 to 120 MPa, with a pressure sensitivity of 5.884 pm/MPa and a measurement accuracy of 0.033 % Full Scale (F.S.), offering both a wide dynamic range and high precision. A modified finite element model (FEM) is developed, incorporating the composite structure of the π-FBG and adhesive interface, to optimize sensor design and improve analytical accuracy. Simulation results confirm the critical influence of structural and bonding parameters on pressure response and successfully predict the wavelength shifts induced by external pressure. The model also reveals key insights into the stress-strain behavior, interfacial strain transfer, and pressure sensitivity. To evaluate temperature effects on pressure sensitivity, controlled experiments were conducted at 2°C, 5°C, 8°C and 20°C, simulating deep-sea temperature environments. The results indicate a linear relationship between pressure sensitivity and temperature. A calibration equation is proposed to compensate for the temperature-induced deviations, maintaining a relative error less than 0.033 % F.S. throughout the 2–20°C range. The sensor features a compact design, straightforward fabrication, and simple calibration procedure, making it suitable for applications in extreme environments, such as deep-sea exploration and downhole pressure measurements. This work advances the analytical framework for π-FBG-based ultra-high-pressure sensors and contributes new insights into the development of next-generation deep-sea measurement technologies.