16-QAM optical packet switching and real-time self-homodyne detection using polarization-multiplexed pilot-carrier

We demonstrated 20-Gbit/s 16 quadrature amplitude modulation (16-QAM) optical packet switching and real-time detection using self-homodyne. A prototype modulator consisting of an in-phase and quadrature (I-Q) modulator and monolithically integrated polarization beam splitters generated modulated signals and polarization-multiplexed pilot-carriers simultaneously. Self-homodyne detection using the pilot-carrier was resilient to phase noise and self-phase modulation, and the constellation was obtained in real time without digital signal processing. A low-polarization-dependent (Pb,La)(Zr,La)O(3) (PLZT) optical switch in the optical packet switch handled both 16-QAM optical packets and the polarization multiplexed pilot-carrier. Even after packet switching, a clear constellation diagram was obtained, and error-free operation was confirmed in real-time using a packet bit-error rate tester (BERT).