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The paper presents two kinds of new optical methods for measuring electric power. They are respectively called indirect optical method for measuuring electric power and direct optical method for measuring electric power. The principles and signal processing technique of the two kinds of methods are discussed comprehensively and systematically. The study shows that the two kinds of methods can be used to measure the electric power when the current is large and/or the voltage is high.

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This paper states the kinds of methods to reduce the low-frequency noise in fiber-optic sensor with frequency-spectrum analysis. The author thinks most of the noise frequency will be mixed with the signal frequency in optic-isolated optical measuring system and the result is the low-frequency noise is shifted to the signal frequency band. So, the low-frequency noise can not simply be removed by band-passed filter in theory. The author discusses kinds of methods treating the lowfrequency noise and puts forward a new one, the method ofA/D conversion. It is an easy realizable, good effective and low cost method for most application.