Fiber optic pressure sensor with self-compensation capability for harsh environment applications

A novel fiber optic pressure sensor system with self-compensation capability for harsh environment applications is reported. The system compensates for the fluctuation of source power and the variation of fiber losses by self-referencing the two channel outputs of a fiber optic extrinsic Fabry-Perot interfrometric (EFPI) sensor probe. A novel sensor fabrication system based on the controlled thermal bonding method is also described. For the first time, high-performance fiber optic EFPI sensor probes can be fabricated in a controlled fashion with excellent mechanical strength and temperature stability to survive and operate in the high-pressure and high-temperature coexisting harsh environment. Using a single-mode fiber sensor probe and the prototype signal-processing unit, we demonstrate pressure measurement up to 8400 psi and achieved resolution of 0.005% (2 sigma=0.4 psi) at atmospheric pressure, repeatability of +/- 0.15% (+/- 13 psi), and 25-h stability of 0.09% (7 psi). The system also shows excellent remote operation capability when tested by separating the sensor probe from its signal-processing unit at a distance of 6.4 km. (c) 2005 Society of Photo-Optical Instrumentation Engineers.