Research On Non-Scanning Correlation Interrogation Technology Of Fiber-Optic Fabry-Perot Sensor

Fiber-optic Fabry-Perot(FP)sensors,can be widely used for accurate measurement of various external physical quantities like pressure,temperature,stress/strain,refractive index,displacement,etc.Furthermore for their advantages of high accuracy,tiny si ze,large dynamic range,simple structure and anti-electromagnetic interfere,etc.,have found many broad applications in aerospace,petroleum,bridge,medical treatment,and so on.For the real applications of fiber-optic FP sensors,the key issue is how to get the measured quantity through cavity length interrogation.Based on the cavity length matching principle,this paper designed and implemented a non-scanning correlation interrogation system for high-precision and large dynamic range measurement of external physical quantities using the combination of optical wedge and CCD linear array.The specific contents are as follows:Firstly,based on the sensing principle of fiber-optic FP sensor,several mam cavity length interrogation methods were compared and analyzed,and the non-scainning correlation nethod was chosen as the interrogation method of this thesis.According to principle of non,scanning correlation interrogation,tlhe mathematical model of the correlation mterferencing signal was established,and the influence of the spectral distribution of different light sources on the signal was discussed.Furthermore,the theoretical analysis and simulation were carried out to verify the feasibility of the using of optical wedge for the cavity length interrogation of FP sensor.Then,overall design of the non-scaiining correlation interrogation system was discussed,including designs of optical path,circuit and software.The optical path design mainly involved the structural optimization of the optical path,the parameter determination of each device and the alignment of the optical path.According to characteristics and performance requirements of the correlation interferencing signal,the digital circuit design mainly realized the FPGA-based control module,the peripheral integrated CCD line array driving module,the A/D signal acquisition module,and the serial communication module.The software development and debugging of each module were completed accordingly.Finally,a test platform was built,the feasibility of the algorithm was verified,and the extraction of the pixel points at the peak position of the correlation interferencing signal was completed.In the calibration experiment,a series of fiber-optic FP sensors with fixed different cavity lengths were used to achieve the calibration of the system through a linearly fitting way;the relationship of the cavity length versus the CCD pixel serial number was gotten.The results show that the accuracy over the full range of 15-105?m reached the measurement error of 0.047%.Subsequently,the diaphragm type fiber-optic FP pressure sensor was connected to the interrogation system,a pressure increasing and decreasing experiment was carried out in the range of 0?3MPa.It was verified that the non-scanning correlation interrogation system can be used in accurate length interrogation of the fiber-optic FP sensor for real applications.