| 摘要 |
PURPOSE: To obtain a high-sensitivity detector for detecting intensity-modified optical signal by mixing an intensitymodified optical signal with signals on the other side before the optical signal is detected in the detector. CONSTITUTION: A mixing state Mst1 is composed of an optical mixer StRK to which an optical signal LS which is modulated in intensity PI by a modulation frequency f1 and from which mixed signals MS (MS1 and MS2) can be fetched. The signals MS are led to the photoelectric detectors PD1 and PD2 of a photodetector DE1. The intensity-modified optical signal LS is converted into an electric signal after the signal LS is mixed with a signal OS having a frequency f0 decided by the frequency f1 before the signal LS is detected in the photodetector DE1. Since no high time resolution is required for a circuit containing working resistors R1 and R2, large resistors R1 and R2 can be used. Therefore, the sensitivity of the photodetector DE1 can be improved remarkably, because the S/Ns of the photoelectric detectors PD1 and PD2 become proportional to the magnitudes of the working resistors R1 and R2 at a given electric signal width. |
