The Research Of Lithium Niobate Waveguide Sine Wave Electric Sensor

How to measure the electric field accurately in a complex electromagnetic environment is more and more important in practical application. Compared with the traditional electrical sensors, optical sensors is more applicable in the field of electric field measurement, because it has the advantages of resistance to electromagnetic interference, smaller size and larger bandwidth, etc. In this thesis, based on the basic principle of integrated optics, we propose to design a lithium niobate waveguide sine wave electric field sensor in order to reduce the interference to original electric field when measuring. We also set up a sine wave electric field sensor system and a nanosecond pulse electric field sensor system, respectively. Meanwhile, the calibration or test for an electric field probe is carried out. Further, a scheme to improve the performance of sensing system is given.First, focusing on the lithium niobate optical waveguide electric field sensor, we introduce the electric field sensor system and comb background and theoretical content related to sensor. Because the lithium niobate waveguide are susceptible to interference of external factors, we control the working point of sensor using the feedback method, and explain the control principle and structure.Second, depending on the low and high frequency electric field measurement requirements, we respectively analyze two different electrode structure of the sensor, combining with the modulation principle of electro-optic modulator and dipole antenna theory.For electrode structure of low frequency electric field sensor, we analyze the influence of the electrode thickness, electrode spacing parameters on the effective refractive index, and make the thickness of the electrodes decrease to zero using Schwartz transform, making numerical analysis more accurate. Considering the results of simulation, we then get an appropriate size of the electrode structure.For electrode structure of high frequency electric field sensor, we adapt electrode structure similar to that of the conical antennas. Then, simulations are carried out by changing the structure parameters, and an appropriate size satisfied the requirement of measuring, can be obtained.Third, we put the sensor system into a prototype, to measure the sine wave electric field, and do the relevant tests. After building the sensor based on the simulation results, we add the wavelength tuning module to the sensor system, and set up electric field sensor system in our paper. Then, we do some tests of it, such as frequency response, linear dynamic. Note that, frequency response test is from 10 kHz to 200 kHz for low frequency electric field sensor, while the scope of high frequency electric field sensor is from 200 kHz to 12 GHz. The measured results indicate that the frequency response of the system is relatively flat, and 12 GHz electric field signal can be detected.Finally, using the similar structure of high frequency electric field sensor, we integrate the nanosecond pulse electric field measurement system, and the nanosecond pulse signals are measured. Numerical results show that, the sensor system can restore information in source electric field well. What’s more, in order to reduce the minimum detectable field of sensor system, we put forward a scheme using EDFA. Test results show that, adding EDFA in front of photoelectric detection module can reduce system noise, increase signal amplitude, thus we can achieve the propose of reducing the size of the minimum detectable field.