| 摘要 |
PURPOSE:To prevent the deterioration of an extinction coefficient according to the decrease of the quantizing efficiency of a laser diode due to a temperature rise by connecting the output of a temperature gain converting circuit to a current source transistor-(TR) of a driving circuit. CONSTITUTION:A temperature gain converting circuit 21 is provided, the output of a time constant circuit 20 constituting an optical output control circuit is branched, connected to the temperature gain converting circuit 21, and the output of the temperature gain converting circuit 21 is inputted to the base of a current source TR 14 of the constant current source of a driving circuit 12. Consequently, since the base voltage of the TR 14 rises as the temperature rises, and a pulse current to drive a laser diode 11 is increased according to the decrease of the quantizing efficiency of the laser diode 11. Thus, even when the laser diode in a 1.5mum band, where the quantizing efficiency decreases at the higher temperature, is used, a transmitting circuit not to degrade an optical waveform and the extinction coefficient can be realized. |
