PURPOSE: To improve the coupling efficiency for light reception by biasing reverse a light receiving element part and a light emitting element part at light reception time to use effectively light incident to the light emitting element part.
CONSTITUTION: A light reception time, common terminals c1 and c2 of a transmission/reception changeover switch 32 are connected to switching terminals b1 and b2, and positive voltage from a driving power source 31 is applied to a rear face electrode 7, and a light emitting element part 20 and a light receiving element part 21 are biased reverse. When the light is made incident from an optical fiber, a light receiving current is flowed through the rear face electrode 7, a P electrode 9 of the light emitting element part, and a resistance 34 and through the rear face electrode 7, a P electrode 8 of the light receiving element part, a diode 35, and the resistance 34 and is detected from output terminals 36 and 37.
TAKEUCHI TSUKASA
SHIMURA MIKIHIKO
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