An electronic driver circuit for a directly modulated semiconductor laser has
a first circuit for generating a constant current and second circuit for modulating
the constant current in dependence on a digital data signal. The modulated current
forms a laser current that drives the semiconductor laser. An optimal signal shape
of the modulated current is guaranteed to the greatest possible extent, even in
the case of high modulation frequencies above one Gbit/s, by way of a third circuit
that is connected in parallel with the semiconductor laser. The third circuit acts
as an ohmic resistance with a high impedance for direct current and with a low-impedance
for alternating current with the modulation frequency.
