| 摘要 |
PROBLEM TO BE SOLVED: To provide a light-receiving circuit for an EOS oscilloscope which accurately converts a light-receiving optical signal into an electronic signal, even if sampling cycle shortens. SOLUTION: Photodiodes 51, 52, connected in series between a positive bias power source 50P and a negative bias power source 50N receive light signals having polarization condition, in response to voltages of measured signals to convert electronic signals. An amplifier 53 amplifies an electronic signal emerging at connection point P of the photodiodes 51, 52. Current monitors 54, 57 respectively detect electronic signals converted with the photodiodes 51, 52 and A/D converters 55, 58 A/D-converts these signals. An adjustment part, consisting of a subtraction circuit 60, adjusts the polarization ratio of the light signal in the direction for reducing the difference between detection values of the current monitors 54, 57, when the monitors light receive reference light.
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