Method and apparatus for frequency modulating a semiconductor laser, and an optical communication system using the same.

摘要

A driving method of the present invention drives a semiconductor laser which is provided with at least first and second electrodes through each of which current is injected into the semiconductor laser. Varying current is injected through the first electrode when the frequency of the varying current is in a high frequency band. Varying current is injected through the first electrode while phase-shifted current, whose phase is shifted relative to the varying current, is injected through the second electrode, when the frequency of the varying current is in a low frequency band which is lower than the frequency of the high frequency band. Feedback-control may be performed for controlling a ratio between amplitudes of the modulation current and the phase-shifted current based on a light output from the semiconductor laser. The varying current includes at least modulation current modulated according to a predetermined signal or negative feedback current produced by an electric signal obtained by detecting fluctuation of oscillation wavelength of a light output from the semiconductor laser. Thus, an optical signal radiated from the laser can be desirably stabilized over a wide frequency band range.