Using LCDF-TEQ to Reduce CP Length for 20.48-Gb/s Direct Detection Optical OFDM Systems Over 1200 km of SMF

In order to reduce the cyclic prefix (CP) length in direct-detection optical orthogonal frequency-division multiplexing (O-OFDM) over 1200 km of single-mode fiber (SMF), a low complexity decision feedback time-domain equalizer (LCDF-TEQ) is proposed. As a result, the residual inter symbol interference (ISI) and inter carrier interference (ICI) caused by both the group velocity dispersion (GVD) and the CP length being shorter than the channel impulse response (CIR) will be cancelled. The recursive calculation of channel matrix inverse reduces the computational complexity. Simulation results show that the performance of LCDF-TEQ is close to decision feedback time-domain equalizer (DF-TEQ) with a much lower complexity.