Enhanced Optical Communications Through Joint Time-Frequency Multiplexing Strategies

We present a power-efficient and reduced-complexity all-optical approach to generate high-bit rate superchannels, based on joint time-frequency multiplexing. Both optical orthogonal frequency division multiplexing (OFDM) and Nyquist-optical time division multiplexing (N-OTDM) signals are generated and processed using a wavelength-selective switch (WSS). We use the fractional Fourier transform (FrFT) to introduce the largest degree of flexibility in optical networking, and we experimentally demonstrate that the transmitted signal can be received either in parallel, as OFDM subcarriers, or in series, as an N-OTDM signal. Compared to conventional optical OFDM, we achieve peak to average power ratio (PAPR) reduction; compared to N-OTDM, we introduce flexible chromatic dispersion (CD) management. We successfully demonstrate a field trial experiment of 4-channel 40 Gb/s hybrid OFDM/N-OTDM transmission over the 89.2-km Japan gigabit network-extreme (JGN X) test bed, with 1 bit/s/Hz spectral efficiency.