20-Gb/s AMO OFDM Transmission Over 20-km Bidirectional Link by Separate I/Q Baseband Delivery Using Remotely Fed 1-GHz RSOAs

We demonstrated a novel 20-Gb/s adaptively modulated optical orthogonal frequency division multiplexed (AMO OFDM) transmission scheme with separate in-phase (I) and quadrature (Q) channel baseband delivery over a 20-km single fiber link using remotely fed 1-GHz reflective semiconductor optical amplifiers (RSOAs) for a colorless optical network unit (ONU). The OFDM symbols with adaptive bit-/power-loading were applied to overcome the bandwidth limitation of RSOAs and to optimize the performance. In order to realize the baseband transmission without Hermitian symmetry, the I and Q channel data streams in the OFDM symbols were separately transmitted by optical carriers at two different wavelengths. Our proposed scheme was experimentally validated using a periodic property of free spectral range (FSR) in a wavelength multiplexer. The separate optical “dual” carriers were provided by the same port of the wavelength multiplexer to avoid wasting the number of wavelength division multiplexed channels.