Research On An Integrated Optical Waveguide Field Sensing System Based On Balanced Detection

The electric field test system is an objective and urgent demand to evaluate the survival ability of various electronic equipment in complex electromagnetic environment,is the test method to evaluate the protection effect,the foundation of the research on the mechanism of electromagnetic damage and the technology of protection and reinforcement,and is one of the most important methods to provide experimental technical support for the research of electromagnetic environmental effects of electronic equipment.Therefore,the accurate measurement of electric field,whether in our daily life or scientific research,will have a very important significance.Many researchers have been committed to the research of measuring electric field.In recent years,the optical sensor technology used in electric field measurement has made great progress,and a variety of corresponding sensors are put forward.Four kinds of optical electric field sensors based on electrostatic attraction,piezoelectric materials,electro-optical crystal and integrated optical waveguide are analyzed.This paper mainly focuses on the integrated optical waveguide electric field sensor and its system which were based on the balance detection and the electro-optical modulation of lithium niobate.The main contents of the thesis are as follows:Firstly,the optical electric field sensor was summarized and the research object was determined.This paper introduced the theoretical basis of Li Nb O₃ optical waveguide electric field sensor,analyzed the structure of Mach Zehnder interferometer,and then leaded to the double parallel asymmetric Mach Zehnder interferometer optical waveguide structure.The structure introduced a fixedπ/2 phase delay,so that the sensor works approximately in the linear working area,and because of the double parallel design,the output of two signals was achieved.Secondly,the segmented electrode was designed on the basis of the double parallel asymmetric Mach Zehnder interferometer optical waveguide structure.Because the segmented electrode was a symmetrical structure and was placed on both sides of the upper and lower parallel waveguide arms,the induced voltage generated on the upper part and the lower part of the segmented electrode is equal in magnitude and opposite in direction,Thus,the phase opposite modulation of the light wave in the upper and lower asymmetrical Mach-Zender interferometer was produced.Two optical signals could be modulated into a pair of symmetrical signals with the same amplitude and opposite phase,which could be used as the differential signals for balanced detection.Then,the balance photodetector was designed for the differential signal output by the sensor.Through the selection of the chip,the design of cross impedance circuit and the use of two PIN photodiodes with the same response could achieve the difference effect,thus suppressing common mode noise in the signal and improving the sensitivity of the sensor system.After the design of the circuit is verified and optimized by LTspice circuit simulation software,a low noise and large bandwidth balanced photodetector was completed by using Altium Designer.Finally,aiming at the integrated optical waveguide electric field sensor and balanced photodetector designed in this paper,the power frequency electric field test system platform was built,and the integrated optical waveguide electric field sensor system based on balanced detection was tested.The test results verify the idea of improving the sensitivity of the optical waveguide electric field sensing system based on balanced detection,and provide a new solution for measuring electric field.