Abstract
In this work, the hysteresis phenomenon of the fiber optic Fabry-Perot interferometric (FPI) pressure sensors is investigated. The method of fabricate EFPI pressure sensors with a high-energy carbon dioxide (CO2) laser as the heating source to thermally fuse tube and fiber is analyzed systematically. Through theoretical analysis and experiments, we find out there are three reasons that cause hysteresis of the EFPI pressure sensors. Firstly, the shape of the two bonding points is not symmetrical around the tube for the ununiformity of energy around the bonding points. That result in the friction between the fiber and the tube will lead to the hysteresis in the EFPI pressure sensors. Secondly, the residual stress in the bonding points produced in the procedure of sensor fabrication will release at HT/HP environments and will also cause hysteresis. Finally, the friction between the fiber and the tube at the bonding points also will result in hysteresis. For solve those problems, a method of insert a spindle-shaped diaphragm in the optical route to improve the energy distribution around the tube is proposed. And a method of putting the EFPI pressure sensor into a high pressure and high temperature environment to level off the residual stress in the bonding points to eliminate hysteresis were demonstrated. Finally, the hysteresis characteristic of an EFPI pressure sensor is experimentally measured after it was improved by the above method, and we can see from the results that the hysteresis of the pressure sensor is eliminated..
Keywords
Fiber optic sensor, Extrinsic fiber Fabry-Perot interferometer, Hysteresis, High pressure, High temperature.
Citation
QI WANG, YONG ZHAO, YA’NAN ZHANG, YUYAN ZHANG, BO HAN, LU BAI, WEI HOU, Study on characteristics of EFPI pressure sensors for HT/HP oilwell, Optoelectronics and Advanced Materials - Rapid Communications, 5, 9, September 2011, pp.1021-1025 (2011).
Submitted at: June 26, 2011
Accepted at: Sept. 15, 2011