To improve the signal quality of the optical signal emitted by a reconfigurable transmitter after a reconfiguration event, an optical transmitter includes a modulator, a digital signal processor, and a controller. The modulator is for modulating light by a driving signal with a reconfigurable format. The digital signal processor is for processing digital data to be transmitted by using parameters in order to generate the driving signal. The controller is for controlling the digital signal processor changing the parameters so as to keep the driving signal stable before and after changing the reconfigurable format.