| 摘要 |
PURPOSE:To receive an optical signal different in frequency with simple circuit constitution by providing a capacitor in parallel with a photo diode so as to change over the capacitor by a switch. CONSTITUTION:Plural capacitors 7a, 7b,... with different capacitance are connected to the junction capacitance of a photodiode 1, the capacitors 7a, 7b,... are selected by a switch 8 to change over the capacitance. Thus, the tuning frequency of a tuning circuit comprising the junction capacitance of the diode 1 and the inductance element 2 connected thereto is switched. Thus, an optical signal having a carrier of a desired frequency is received with tuning. |
