Experimental demonstration of a cost-effective bit rate variable IM/DD optical OFDM with reduced guard band

We experimentally demonstrate an intensity modulated and direct detection optical OFDM with variable bit rate from 5 Gb/s to 9 Gb/s using BPSK format. A fast processing based on the Hartley transform is performed with low complexity DSP, achieving the same performance as 4QAM FFT-based processing. Using the same bandwidth occupancy as required for 5 Gb/s, the bit rate can be increased up to 80% and transmitted over 25 km SSMF, by reducing the guard band and adopting an optimized transceiver design with additional overhead, including half-length training symbols and cyclic extension.