Single-Channel 1.92 Tbit/s, 64 QAM Coherent Nyquist Orthogonal TDM Transmission With a Spectral Efficiency of 10.6 Bit/s/Hz

We have proposed a coherent optical Nyquist pulse and its high-speed optical time division multiplexing (OTDM), in which data signals can be transmitted at a bandwidth as low as the baud rate. By taking advantage of the time-domain orthogonality of coherent Nyquist pulses, Nyquist OTDM signals can be demultiplexed with a high SNR, despite a large intersymbol overlap by adopting Nyquist-LO pulses. With this technique, we successfully transmitted a 1.92 Tbit/s, polarization-division-multiplexed 64 quadrature amplitude modulation Nyquist pulse signal over 225 km within a signal bandwidth of 170 GHz, leading to a potential spectral efficiency of as high as 10.6 bit/s/Hz.