| 摘要 |
PROBLEM TO BE SOLVED: To operate the optical transmitter at an optimum bias point at all times by controlling the bias quantity of a semiconductor laser injection current, so as to minimize a semiconductor laser distortion detected from an electric signal resulting from applied photoelectric conversion to a semiconductor laser output light. SOLUTION: A CATV signal and a radio signal or the like are received from a signal input 4, and a signal driver 5 amplifies them to a level proper for driving by a semiconductor laser 1. A coupler 6 couples the output of the signal driver 5 with a bias current which is an output of a bias current source 8, and this output drives the semiconductor layer 1. Then the semiconductor laser 1 outputs an optical signal, whose light intensity is changed in proportion to a change in an injection current. An optical branching coupler 2 branches part of the output optical signal, and a photoelectric converter applies electric conversion to the optical signal. A distortion detection section 7 detects distortion from the electric signal obtained. Then a bias current controller 3 decides a bias current to minimize the distortion detected by the distortion detection section 7 for controlling the bias current source 8. |
