| 摘要 |
PURPOSE:To provide link monitor function by providing a photodetector for link monitor receiving the light reflected by a projected transparent body of a main photodetector and a link monitor circuit amplifying an optical current of the link monitor photodetector, and detecting the presence of the light incidence. CONSTITUTION:An optical fiber 1 is aligned and fixed to the main photodetector 2 for signal reception connected to an optical reception circuit and one or plural monitor use photodetectors 3 are provided in the oblique front direction of the signal reception photodetector 2. In touching the reflected light to the monitor photodetector 3, since the reflected light 4 returned to an optical fiber end face is less than that going aside, the light is made well incident to the monitor photodetector. The optical current of the monitor photodetector element 3 is amplified by the link monitor circuit. The link monitor circuit is entirely independent of the signal circuit, which amplifies and binarizes the light current of the main photodetector 2. The link monitor circuit has only to apply DC amplification to the output of the monitor photodetector and no peak hold circuit is required. |
