Electro-optical measurement of highly intense electric field with high frequency

摘要

The transient electric field of highly intense electromagnetic pulse (EMP) will seriously damage the military and civil installations, so it is significantly important to measure such electric field of EMP with high frequency. This paper describes a fiber-optic sensor for measuring highly intense electric field with high frequency. The sensor consists of a probe of electrooptic(EO) crystal, optic fiber, polarizer, photodetector, processing circuits and single-chip microprocessor. According to Pockels effect, the polarized light will be modulated by the electric field to be measured when it penetrates the EO crystal. Then, its polarized direction will vary following the variation of electric field. The change of polarized direction is converted to the variation of light intensity by polarizer. In order to gain good performance, it is important to choose suitable crystal carefully. The interrelated optical axises of the components are adjusted on the basis of the theoretical analysis and calculations. A special temperature compensating method is used to decrease the temperature effect. At the meantime, the low noise circuit is used. The testing results show that the linearity is 0.2percent, the error of the measurement is approximately 0.5percent and the risetime is less than 4ns.