Diaphragm-Free Fiber-Optic Fabry-Perot Interferometric Gas Pressure Sensor for High Temperature Application.

Hao Liang,Zhe Li,Jijun Xiong,Jia Liu,Pinggang Jia,Ting Liang,Yingping Hong,Guocheng Fang

doi:10.3390/s18041011

Abstract

A diaphragm-free fiber-optic Fabry-Perot (FP) interferometric gas pressure sensor is designed and experimentally verified in this paper. The FP cavity was fabricated by inserting a well-cut fiber Bragg grating (FBG) and hollow silica tube (HST) from both sides into a silica casing. The FP cavity length between the ends of the SMF and HST changes with the gas density. Using temperature decoupling method to improve the accuracy of the pressure sensor in high temperature environments. An experimental system for measuring the pressure under different temperatures was established to verify the performance of the sensor. The pressure sensitivity of the FP gas pressure sensor is 4.28 nm/MPa with a high linear pressure response over the range of 0.1–0.7 MPa, and the temperature sensitivity is 14.8 pm/°C under the range of 20–800 °C. The sensor has less than 1.5% non-linearity at different temperatures by using temperature decoupling method. The simple fabrication and low-cost will help sensor to maintain the excellent features required by pressure measurement in high temperature applications.

Highlights

Compared with conventional pressure sensors, fiber-optic pressure sensors are widely used for pressure measurement of gases under high temperature because of their advantages of resistance to harsh environments, immunity to electromagnetic interference, small size and high sensitivity [1,2,3,4]
This paper proposes a diaphragm-free fiber-optic Fabry-Perot (FP) interferometric gas pressure sensor
A diaphragm-free fiber-optic gas pressure sensor for high temperature environments based on pressure changes with gas density, which provides a method of pressure measurement at high temperature is presented

Summary

Introduction

Compared with conventional pressure sensors, fiber-optic pressure sensors are widely used for pressure measurement of gases under high temperature because of their advantages of resistance to harsh environments, immunity to electromagnetic interference, small size and high sensitivity [1,2,3,4]. Wang et al [11] presented a fiber Fabry-Perot interferometer and a fiber Bragg grating-based pressure and temperature multiplexed sensor system with pressure and temperature measurement accuracy of 0.03 Mpa and 0.5 ◦ C in the temperature variation range between 18 ◦ C. Demonstrated a diaphragm-free pressure sensor which realized pressure measurements from room temperature to 700 ◦ C made by splicing a SMF to a photonic crystal fiber (PCF) with a hole fabricated by a 157-nm laser at the end of the PCF. The measurement results of the above sensors are affected by the thermal expansion and the elastic modulus change of the material when applied in a high temperature environment which seriously affects the sensor accuracy. This paper proposes a diaphragm-free fiber-optic Fabry-Perot (FP) interferometric gas pressure sensor. The sensor has the advantages of simple structure, low cost, simple fabrication, low temperature coefficient, high accuracy and it can work stably at a high temperature of 800 ◦ C and hopefully be used at a higher temperature

Operating Principle

Optical Interference Principle

Temperature Decoupling Principle

Sensor Fabrication

Experiments and Results

Conclusions