Switchable UWB pulse generation using a phase modulator and a reconfigurable asymmetric Mach-Zehnder interferometer.

We propose a new scheme to generate polarity-switchable ultrawideband (UWB) Gaussian pulses in the optical domain by use of a phase modulator and a reconfigurable asymmetric Mach-Zehnder interferometer (AMZI). In the proposed system, an optical carrier is phase modulated by a Gaussian pulse train and then sent to a first-or second-order AMZI. The system is equivalent to a first- or second-order differentiator for the production of Gaussian UWB monocycle or doublet pulses. The polarity of the generated UWB pulses can be switched by adjusting the phase difference between the two interference components in the AMZI. An experiment is performed. Gaussian monocycle and doublet pulses with fractional bandwidths of about 177% and 140% are generated. The polarity switchability of generated UWB pulses is also experimentally confirmed.