Abstract: Methods and apparatus for supporting a plurality of modulation formats using a single transmitter are disclosed. According to one aspect of the present invention, a transmitter arrangement that provides a signal to a modulator that creates an optical data stream from the signal includes an encoder and a switching/filtering arrangement. The encoder has a state that is varied between first and second encoder states. If the state is the first encoder state, the encoder encodes the signal in a format associated with an optical duobinary (ODB) modulation format. Otherwise, the encoder does not encode the signal in the format associated with the ODB modulation format. The switching/filtering arrangement receives the signal from the encoder, and provides the signal to the modulator. If the variable state of the encoder is the first encoder state, the switching/filtering arrangement has a low bandpass configuration. Otherwise, the switching/filtering arrangement has a high bandpass configuration.