Performance analysis of decision feedback time domain equalizer for direct-detection optical OFDM transmission in long-distance SSMF

Optical Orthogonal Frequency Division Multiplexing (O-OFDM) provides major advantages in mitigating Group-Velocity Dispersion (GVD) in Single-Mode Fiber (SMF). Unfortunately, substantial dispersion is accumulated in long-haul transmission, leading to a longer Cyclic Prefix (CP). This effect sets some limitations on the overall throughput and the spectral efficiency. On the other hand, if the CP length is shorter than the Channel Impulse Response (CIR), the system performance is limited by the Inter Symbol Interference (ISI) and Inter Carrier Interference (ICI). We propose a Time-Domain Equalizer immediately after the channel. Numerical simulation shows the cancellation of residual ISI and ICI caused by both GVD and CP length being shorter than the CIR.