Design of Optical Fiber Fabry-Perot Sensors Based on Intensity and Phase with Parallel Processing

For fiber Fabry-Perot sensor vulnerable to external parameters such as electromagnetic, noise and displacement impact, reducing the problem resilience, research and design new fiber Fabry-Perot sensor with parallel processing capabilities based on the intensity and phase of perception. First, according to various types of external parameters and the degree of interference, established the intensity and phase-oriented demodulation algorithm then gives a fiber Fabry-Perot microcavity sensor performance analysis model is then proposed for the fiber Fabry-Perot sensor has a solution parallel processing algorithms tune transformation, and finally developed a fiber Fabry-Perot sensor has strong adaptability and measurement effects. Experimental results show that the single phase demodulation and intensity demodulation fiber Fabry-Perot sensor design compared to the proposed sensor design has obvious advantages in accuracy and performance of the strain. Keywords: Intensity, optical fiber fabry-perot sensor, parallel processing, phase. 1. INTRODUCTION The internal optical fiber Fabry Perot sensor design has two story high reflection films. The parallel arrangement formed a narrow cavity, which is shown in Fig. (1). L denotes the micro cavity length. When the external beam through the optical refraction to the micro cavity, the emission film interlayer reflection would be returned. At the same time, there is the beam multiplexing interference and distortion phenomenon, etc. The detection value could be obtained by checking the output signal according to the micro cavity length. The optical fiber Fabry Perot cavity would be deployed in the monitoring object after connecting the fiber. The status of output beam could be changed and the parameter settings status would be perceived on the basis of sensing the small changes of the environment with Fabry Perot strong induction, which has been used in the fields of bridge strain [1] and anti-shock grating strain sensor [2]. There are some research results of the demodulation, strain, anticorrosion and so on. The non-scanning the cavity length information is used to decode the non-scanning Multi-channel fiber optic Fabry Perot [3], the authors researched the optical model of demodulation system of optical fiber Fabry Perot sensor. For designing the transverse, longitudinal and tangential regulation of strain measurement adaptive direction, the article [4] proposed the Fiber Bragg grating strain sensor based on the similar material model. L J Jiang et al. [5] researched the cavity length analysis method by approximating the Fiber optic Fabry Perot pressure sensing to the signal envelope spectrum curve signal spectrum curve. Y J Rao et al. [6] proposed the optical fiber Fabry Perot sensor with the germanium chemical corrosion of boron has the advantages of simple structure, portable and low cost of Co doped fiber fabrication. Light beam Composite module Separator fiber High reflection film Fig. (1). Optical fiber fabry perot sensor structure. Huizu Lin et al. [7] analyzed the phase carrier generated by the mode crosstalk and the embedded time division optical fiber Fabry Perot sensor system by multiple reflection. L H Li et al. [8] proposed the small volume and low cost optical system based on the non-scanning correlation demodulation cavity length information. Yong Zhao et al. [9,10] proposed the FP optical fiber magnetic field sensor with temperature compensation model by combining the characteristics of Fiber Prague grating temperature sensing. In order to reducing the influence with the Electromagnetic noise and the external parameters, such as displacement on the Fiber Fabry Perot sensor strain capacity, there are the following contributions in our research. First, the Analysis of performance model and the combined demodulation scheme were proposed based on the influence characteristics of intensity and phase demodulation of the long Fabry Perot cavity. Second, we designed the combined demodulation conversion circuit based on the intensity and Design of Optical Fiber Fabry-Perot Sensors The Open Automation and Control Systems Journal, 2015, Volume 7 2147 phase orientation. Finally, the new optical fiber Fabry Perot sensor was researched on the view of the above results. 2. MICRO CAVITY PERFORMANCE ANALYSIS MODEL The communication performance of optical fiber Fabry Perot sensor is mainly affected by the length of cavity, which cause that the output signal beam of demodulation has different selectivity. However, the status of cavity length is easily to be disturbed by the external parameters, which include the external force, optical fiber Fabry Perot displacement, deformation, environment temperature, voltage and current, etc. The phase PH and intensity IN of optical fiber Fabry Perot sensor with the process of modulation and demodulation have the most obvious interference from the above parameters. The Fabry Perot interferometer is shown in Fig. (2). High reflection film incident beam L intensity phase Output signal external parameters Fig. (2). Process of external parameters interference. The output signal IR could be obtained by the emission and transmission combined with the external parameters after the phase demodulation, which is given by formula (1). IR = 2d cosα 1+ cos 1 2 α d 2 − d0 2 PH (1) Here, let α denote the refraction radian which could be obtained by formula (2).