According to the present invention, an optical transmitting system, which
enables a precise control of the power and the extinction ratio of the optical
output without a small amount of the preset data, will be provided. The system
comprises a laser module and a control system that supplies a bias current and
a modulation current to the laser module. In the present invention, one of the
bias current and the modulation current of the semiconductor laser in the laser
module is varied to maintain the power and the extinction ratio of the optical
output, and the other of the bias current and the modulation current is calculated
based on the specific function. Only coefficients of the specific function are
stored in the control system. Therefore, the present invention does not need a
large size of the storage in which both the bias current and the modulation current
are stored as a table.
