Study On The Interferometric Temperature-pressure Distributed Fiber Optic Sensor

With the continuous popularization and development of the optical fiber sensing technology,the distributed optical fiber sensing technology has been more and more get the attention of people.Two types of optical fiber sensing system which can measure both temperature and pressure were proposed in this paper.The first one was a new kind of Fabry-Perot interferometer fiber sensor.We spliced a bit of multimode optical fiber into a long period of single-mode fiber to form Fabry-Perot cavity.The second one was a distributed optical fiber sensor combined by polarized light interference and side-hole fiber.The first kind of sensor was a multipoint measurement,it can be regarded as quasi-distributed sensing system.And the second sensor was a distributed sensing system.For the first optical fiber sensor system,we analyzed its temperature,stress and pressure sensing theory,and used multiple peak tracing method to write the demodulation algorithm.In experimentation we made the physical sensors of this kind and built the fiber optic sensor measurement system to do the quasi distributed temperature-pressure measurement experiment.The experimental results showed that this sensing system can be response to ambient temperature and pressure.The repeatability and sensitivity was good so it can measure temperature and pressure.Because the first optical fiber sensor system was a quasi-distributed sensing system.We proposed the second distributed fiber optic measuring system which was combined by polarized light interference and side-hole fiber.This kind of sensor system mainly used the birefringence response of the side-hole fiber to measure pressure and temperature outside.The birefringence sensing mechanism of pressure and temperature was analyzed And a two-way polarized light interference experiment light road was designed.The finite element analysis software ANSYS was used to analyze the side-hole fiber to get the birefringence changes by the influence of pressure and temperature changes outside.And the influence of side-hole fiber structure parameters to the pressure sensitivity and temperature sensitivity wasanalyzed which was helpful to improve the pressure and temperature sensitivity coefficient in practical engineering.