fading in direct-detection (DD) optical orthogonal frequency-division multiplexing (OFDM)
system. We also proposed and experimentally demonstrated a novel DD OFDM
transmission scheme with pre-emphasis technique. By pre-emphasizing the power of the
OFDM subcarriers at the high frequency, the received sensitivity at our experiment was
improved about 2 dB at a bit error rate of $1 x 10^-4 after 100-km SMF-28 transmission …