| 摘要 |
PURPOSE:To emit a specific quantity of light from a light source even in case of temperature variation and to reduce the cost by braching an optical signal from a laser diode and sending it to an optical fiber and a 1st photodetecting element, and bending an optical signal from an opposite side and sending it to a 2nd photodetecting element. CONSTITUTION:The laser light from the laser diode 22 is branched by a beam splitter 30 in two directions, one light beam is sent to the opposite side from the optical fiber 25, and the other laser light beam is sent from the 1st photodetecting element 27 to an APC circuit 48, so that the quantity of the light of the laser diode 22 is controlled to a specific quantity. When an optical signal is received, on the other hand, the optical signal which is transmitted through the optical fiber 25 is branched by the beam splitter 30 and sent to the 2nd photodetecting element 28, and the signal is converted into an electric signal corresponding to the optical signal. This electric signal is passed through an AGC circuit 45 and a decoding circuit 46 and converted into a voice signal and a buzzer signal. The optical signal from the optical fiber 25 is sent to the laser diode 22 by the beam splitter 30 as well, but this optical signal is not used for optical signal reception. |
