THEORETICAL-ANALYSIS OF THE SENSITIVITY OF ELECTRIC-FIELD SENSORS USING LINBO3 OPTICAL MODULATOR

The electric field sensor using an optical modulator makes possible ac curate measurement without disturbing the electromagnetic field to be measured and is expected to have applications in EMC measurement. In t his paper, a theoretical analysis of the sensitivity of the electric f ield sensor using an LiNbO3 modulator and the error factors are descri bed. 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, tho se related to the sensor rod are derived by a numerical analysis using the method of moments. Those related to the optical modulator are der ived by the theoretical analysis and measurement. A method is presente d for determination by measurement in regard to the optical source and the detector. An electric field sensor is fabricated and its characte ristics are evaluated. It is found that the difference between the mea sured value and the theoretical value of the sensitivity is about 8.2 dB. The causes of the difference are the input capacitance and the ins ertion loss of the optical modulator. These two parameters are measure d 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 sensit ivity analysis of the electric field sensor. (C) 1997 Scripta Technica , Inc.