| 摘要 |
PROBLEM TO BE SOLVED: To provide a light transmitter which can precisely control a quenching ratio even if the output characteristic of a current to light in a laser diode changes by detecting the fluctuation of the quenching ratio with the output amplitude fluctuation of a preamplifier thereby controlling bias current. SOLUTION: A digital signal inputted to a DATA input terminal 1 is converted into modulation current Imod and it drives a laser diode 3 with bias current Ib. A part of a light signal outputted from the laser diode 3 is inputted by a photodiode 5 and is converted into a current signal. The current signal is converted into a voltage signal by a preamplifeir 6. A voltage amplitude value is kept by capacitive load by a peak detector 7 and a voltage value proportional to the voltage amplitude value is outputted. A bias current controller 8 inputs output voltage and controls the size of bias current Ib outputted from a bias current source 4 so that inputted voltage becomes constant. |
