PURPOSE: To achieve a higher stability in conversion loss of an antenna by a method wherein a photoelectric power emitted from a light modulator is detected and an output level of a photo detector is corrected by a correction means according to a level thereof to eliminate dependence of the conversion loss of the antenna on the level of an outgoing light of a light source.
CONSTITUTION: A photoelectric power P1 to be emitted from a light source 1 is set with a directional coupler 15 set on the side of the light source 1 of a system in which an antenna for detecting intensity of an electric field is inserted to measure an intensity of an electric field accurately without disturbing an ambient electromagnetic distribution and a photoelectric power P2 emitted from a receiver 13 having a light modulator is set with a directional coupler 15 set on the side of a photo detector 11. When a signal is small sufficiently with respect to an amplitude of light wave, a ratio P2/P1 of powers P1 and P2 is determined by a specified computation, thereby enabling a measurement compensated for a change in photoelectric power of the light source 1 and a change in intrinsic phase value of a crystal.
AMAMIYA FUJIO
TOKUDA MASAMITSU
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