| 摘要 |
PURPOSE: To prevent damage to a photodetector by background light and the malfunction of an angle correction function. CONSTITUTION: Transmission signals are synthesized with pilot signals in a synthesizer 3 and transmitted from an optical axis angle adjustment driving mechanism part 8 to an opposite side equipment. Reception light transmitted from the opposite side equipment is passed from the optical axis angle adjustment driving mechanism part 8 through a first beam splitter 6 and a second beam spliter 9 and main signals are received in a main signal reception part 10. In the meantime, the reception light on which the background light is superimposed is received by an angle deviation detection part 12, and when it is judged that the background light is at an excessive optical level, an optical axis angle adjustment driving control part 13 drives the optical axis angle adjustment driving mechanism part 8, changes the direction of a mirror system 7, prevents excessive light from being made incident on the photodetector of the angle deviation detection part 12 and the main signal reception part 10 and recovers a normal communication state after the lapse of the prescribed period of time. |
