All-Optical Switching of QPSK Signals for 100 G Coherent Systems

We propose a novel method for signal processing of phase-modulated signals suitable for 100 G coherent systems. By exploiting a single semiconductor optical amplifier Mach-Zehnder interferometer, all-optical selective switching with simultaneous wavelength conversion of bursts of data in the original signal is demonstrated. The operation is suitable for dynamic wavelength routing and/or add/drop operation in multichannel coherent systems, thus enabling flexible network resources optimization. The operation has been demonstrated for single-channel single-polarization, dual-channel (DC) single-polarization, and DC polarization-multiplexed (PM) 28 GBaud quadrature phase shift key-modulated signals. By exploiting coherent detection strategy and digital signal processing, an error rate below 10^-3 prior to forward error correction has been observed for all the experiments; the corresponding optical signal-to-noise ratio penalty has been measured to be almost negligible in the single-polarization case whereas a maximum penalty below 1.5 dB for the PM one is reported.