Examples disclosed herein relate to optical driver circuits. In some of the disclosed examples, an optical driver circuit includes a pre-driver circuit and a main driver circuit. The pre-driver circuit may include a pattern generator and at least one serializer to generate a main modulation signal and an inverted delayed modulation signal. The main driver circuit may include a level controller to control amplitudes of pre-emphasis on rising and falling edges of a modulation signal output and an equalization controller to transition the modulation signal output from the pre-emphasis amplitudes to main modulation amplitudes using the inverted delayed modulation signal.