# A Cylindrical High-Temperature-Resistant Fiber-Optic Composite Sensor for Temperature and Pressure Measurement

## TL;DR

A new fiber-optic sensor can measure temperature and pressure in extreme conditions up to 600°C.

## Contribution

A cylindrical sensor using EFPI-FBG structure enables stable high-temperature and high-pressure sensing.

## Key findings

- The sensor achieves a pressure sensitivity of 0.171 μm/MPa with high linearity.
- It operates reliably at temperatures up to 600°C and pressures up to 20 MPa.
- A decoupling matrix allows accurate separation of temperature and pressure measurements.

## Abstract

This study proposes a cylindrical high-temperature-resistant fiber-optic composite sensor based on the EFPI-FBG hybrid structure for simultaneous temperature and pressure measurement, addressing the demand for high-performance monitoring in harsh environments. The sensor’s core consists of a cylindrical pressure chamber, a metal substrate, and an EFPI-FBG sensing structure fixed via resistance welding and high-temperature ceramic adhesive. The cylindrical pressure chamber converts pressure into axial deformation to modulate the EFPI cavity length, while the FBG with one end floating is exclusively used for temperature compensation, avoiding pressure interference. The EFPI cavity length exhibits a linear relationship with pressure, achieving a sensitivity of 0.171 μm/MPa and a linear correlation coefficient of 0.9986. Stable operation up to 600 °C and 20 MPa is demonstrated, with a decoupling matrix enabling accurate dual-parameter sensing.