| 摘要 |
PURPOSE:To improve the transmission efficiency by separating a semiconductor laser and an amplifier circuit at transmission so as to eliminate the need for a switch connected at reception and connecting a transmission reception changeover control circuit between both terminals of the semiconductor laser at reception so as to decrease a time till a reception time is made stable. CONSTITUTION:When a semuconductor laser 12 outputs an optical signal in response to a transmission signal in the case of transmission, a gate circuit 41 interrupts an output of a comparator circuit 24 to fix an output of a level fluctuation circuit 25 to a low level even when an output voltage of a preamplifier 22 is fluctuated. On the other hand, in the case of reception, a switch 11 is open and a switch 26 is closed to set the reception mode. A reference voltage Vref is applied to the semiconductor laser 12 via the switch 26, which acts like a light receiving element. Then a transmission reception changeover control circuit is connected between terminals of the semiconductor laser 12 to discharge an undesired charge in the semiconductor laser 12 and then the reception is entered thereby reducing the time till the reception is made stable. |
