Comparison of LMS-TEQ and DF-TEQ to reduce cyclic prefix length in direct detection optical OFDM system

This paper presents the comparison of using least mean square time-domain equalizer (LMS-TEQ) and decision feedback time-domain equalizer (DF-TEQ) to reduce cyclic prefix (CP) length for direct-detection of optical orthogonal frequency division multiplexing (O-OFDM) over 6960 km of single mode fiber (SMF). Both TEQs are used immediately after the channel. Numerical modeling results show that they can cancel 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). Using these TEQs allow the reduction of CP length, and consequently leading to system performance improvement. On the other hand, each of TEQs adds complexity to the system. Therefore, the aim of this paper is to analyze and compare the performance of LMS-TEQ and DF-TEQ while considering different CP length and complexity.