Optical Multicasting of 16QAM Signals in Periodically-Poled Lithium Niobate Waveguide

We experimentally demonstrate multicasting operation of a 16QAM signal, by simultaneously generating multiple copies of the signal through optical wavelength conversion in a single periodically-poled Lithium Niobate (PPLN) waveguide. The simultaneous conversion of the signal on multiple wavelengths is based on the cascade of sum frequency generation and difference frequency generation second order nonlinear effects taking place in the PPLN. Each conversion is potentially tunable in the whole C-band and polarization independent operation is achieved by embedding the PPLN in a polarization diversity scheme. A first experiment reports a 3-fold wavelength conversion of a single polarization 112 Gb/s 16QAM signal. Both DFB lasers and ECLs are used to generate the optical pump signals employed in the scheme; the impact of different phase noise amounts induced by the pumps on the BER curve behavior is also discussed and numerically verified. A second experiment reports a 2-fold wavelength conversion of a 224 Gb/s polarization-multiplexed (PM)-16QAM signal, thus confirming the correct operation for PM signals. At last, the multicasting operation on the PM-16QAM signal is successfully employed in a WDM metro network scenario.