Theoretical analysis of the sensitivity of electric field sensors using LiNbO3 optical modulator.

The electric field sensor using an optical modulator makes possible accurate measurement without disturbing the electromagnetic field to be measured and is expected to have applications in EMC measurement. In this paper, a theoretical analysis of the sensitivity of the electric field sensor using an LiNbO3 modulator and the error factors are described. First, the electric field sensor consisting of a rod, an optical modulator, an optical source, and an optical detector is expressed by an equivalent circuit. Next, of the equivalent circuit parameters, those related to the sensor rod are derived by a numerical analysis using the method of moments. Those related to the optical modulator are derived by the theoretical analysis and measurement. A method is presented for determination by measurement in regard to the optical source and the detector. An electric field sensor is fabricated and its characteristics are evaluated. It is found that the difference between the measured value and the theoretical value of the sensitivity is about 8.2 dB. The causes of the difference are the input capacitance and the insertion loss of the optical modulator. These two parameters are measured beforehand and used in the calculation. Then, the sensitivity of the electric field sensor can be estimated with an accuracy of 1 dB. The analysis method used in this paper is found to be effective for sensitivity analysis of the electric field sensor. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 1, 80(12): 79–89, 1997 [ABSTRACT FROM AUTHOR]