| 摘要 |
PURPOSE:To keep the level of a synthesized output light of a laser diode which outputs a modulated light with prescribed level against temperature change and another laser diode exclusive for use in bias adjustment. CONSTITUTION:An optical transmitter 1 is provided with the 1st laser diode 21a subjected to modulation at a prescribed level with an output current of a current driver 31 and a bias setter 46 and the 2nd laser diode 21b adjustable for a bias light leve. The output light of the 1st and 2nd diodes 21a and 21b is synthesized at an optical directional coupler 24 and the synthesized output is monitored at a photodiode 23. The monitored output is applied to one input of a differential amplifier 44 and a voltage difference with the reference voltage of a reference voltabge generator 45 inputted to another input of the amplifier 44 is obtained, a bias current Ib set to a prescribed temperature is applied to the diode 21b, the output level of the diode 21b is adjusted and the synthesized output light level can be kept constant. |
