| 摘要 |
PURPOSE:To obtain maximum reception sensitivity, by setting a value of a load resistor connected to a photodetector to an optimum value in response to the speed of a signal automatically, in an optical reception circuit having a constant mark rate. CONSTITUTION:In case of a feedback type reception circuit, after an optical signal inputted to a photodetector 5 is amplified at an amplifier 6, it is outputted as a pulse from a pulse shape circuit 7, the signal speed is detected as the pulse density and applied to a pulse density detection circuit 8 and a pulse density- voltage converting circuit 9, where a control voltage or current in response to the signal speed is obtained and given to a variable load resistor 10 to control the resistor so as to obtain maximum reception sensitivity. As a variable load resistive element, an indirect heating thermister or a field effect transistor is used. The same operation can be obtained for a reception circuit without feedback. |
