PURPOSE: To miniaturize a circuit by constituting an optical PFM demodulation circuit with an optical signal converting element and plural passive elements only so as to simplify a circuit constitution remarkably more than a conventional circuit constitution in spite of having the same degree of the PFM demodulation characteristic.
CONSTITUTION: An optical PFM signal is irradiated to an optical signal converting element D constituting a part of a series resonance circuit 20 through an optical fiber 11. The said series resonance circuit 20 is constituted by connecting a coil L and the 1st capacitor C1 sequentially between the anode and cathode of the element D. A capacitor charge circuit 21 is connected to the series resonance circuit 20, the capacitor charging circuit 21 is connected across the 1st capacitor C1 and the 1st capacitor C1 is charged via the 1st resistor R1 from a power supply E0 such as a battery. Further, the 2nd resistor R2 and the 2nd capacitor C2 are connected across the capacitor C1 from the connecting point between the coil L and the 1st capacitor C1 sequentially and the 2nd resistor R2 and the 2nd capacitor C2 constitute an integration circuit 22.
FURUKAWA RYOZO
IIO YORIO
WATANABE NOZOMI
