| 摘要 |
PURPOSE:To improve the reliability and to obtain an optical transmitter where the output level of an auxiliary signal is not varied regardless of the change of the mark rate of a transmission main signal by providing a modulation current selecting circuit consisting of an adjusting circuit which adjusts the signal level of the auxiliary signal and a changeover switch connected in parallel to the adjusting circuit. CONSTITUTION:A transistor TR 16 is provided in parallel with a TR 5, and TRs 5 and 16 constitute a current mirror circuit. A series-parallel circuit of resistors 19 and 20 and a capacitor 21 and a changeover switch 22 are connected in parallel to the collector of the TR 16, and a resistor 17 which has one terminal connected to a power source 20 and a series circuit of a capacitor 14, which has one terminal connected to an auxiliary signal input terminal 23, and a resistor 18 are connected. Thus, the number of constituting parts is reduced, and the optical output level of the auxiliary signal is not changed though the optical output is switched to change the mark rate of the transmission main signal, and therefore, the economical equipment constitution is obtained. |
