Research On Low Coherence Interferometry Demodulation System And Its Performance Based On Large Core Diameter Optical Fiber

Low coherence interferometry is an effective way to measure absolute distance,and is widely used in all measurements of physical quantity that can be converted into distance or displacement information.The spatial scanning low coherence interference demodulation system based on birefringent crystal wedge possesses satisfied long-term stability,because it has no moving parts.However,the light source coupling efficiency of the system bears a low efficiency,and this has been limited the ratio of the signal-to-noice of interference signal.Therefore,this paper starts with improving the coupling optical power of multimode fiber.The demodulation system is built by using an adjustable linear voltage stabilized power supply and large core diameter optical fiber.The performance of each part of the low coherent interference demodulation system based on large core diameter optical fiber is studied.On this basis,the consistency and demodulation rate of the demodulation system are studied,and the compensation method of optical wedge position offset is proposed.The accurate demodulation of the same sensor source on any different demodulation module is successfully applied.A demodulation system of large-core fiber with high efficiency was designed and built;the function of continuous acquisition and demodulation of interference signal is realized.The specific research contents of this paper are as follows:1.Based on the performance of white LED light source made by large core diameter optical fiber,the incident light power and interference spectrum of different core diameter optical fiber demodulation systems are compared and analyzed comprehensively.The experimental results show that the optical power of the large core diameter optical fiber LED light source entering the demodulation system is about 100 times that of the ordinary optical fiber.Based on the optical path tracing model of demodulation module,a cylindrical lens suitable for coupling light of large core diameter fiber is simulated and designed to improve the light intensity of large core diameter fiber incident on the imaging surface of CCD.2.The consistency and demodulation rate of large core diameter optical fiber demodulation system are studied and tested respectively.The research on the consistency of the demodulation system includes the calibration of the standard demodulation module as a reference and the position compensation of the optical wedge position offset demodulation module.The experimental results show that: The same demodulation device only needs to be calibrated once to demodulate the source of non-simultaneous interpretation within any range of scanning optical path difference.The same sensing source can be demodulated on different demodulation device,and the relative error of the demodulated optical path difference is less than0.2%.3.In order to realize the demodulation rate of large core diameter demodulation system,the software operation function is optimized based on the built hardware system,and the functions of continuous acquisition and real-time demodulation are added.The acquisition rate of the system is 263.16 frames per second.Finally,the overall package design of the large core diameter demodulation system is carried out to realize the miniaturization and integration of the demodulation module.