Demonstration of 4 $\times$ 128-Gb/s DFT-S OFDM Signal Transmission over 320-km SMF With IM/DD

Intensity modulation and direct detection (IM/DD) is a promising solution for short-reach links. In this paper, we experimentally demonstrate transmission of 128-Gb/s discrete Fourier transform (DFT)-spread 16-ary quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) signals in an IM/DD optical system. Vestigial sideband (VSB) modulation with 20-dB suppression ratio enabled by a cost-effective interleave or a tunable optical filter (TOF) is employed to eliminate chromatic dispersion (CD) induced power fading. Meanwhile, a combination of advanced digital signal processing (DSP) algorithms, such as pre-equalization, nonlinearity equalization (NE), and decision-directed least mean square (DDLMS), are utilized to mitigate the system distortions and improve system performance. By using this scheme, the 32-GBd DFT-spread OFDM signals can be successfully transmitted over 320-km standard single mode fiber (SSMF) with the measured bit error ratio (BER) under the soft-decision forward-error-correction (SD-FEC) threshold of 2 × 10
^-2
. We also achieved 144-Gb/s for 80-km SSMF transmission. Additionally, 4 × 128-Gb/s wavelength division multiplexing (WDM) DFT-S OFDM signals transmission over 320-km SSMF is experimentally investigated. To the best of our knowledge, this work reports the longest transmission distance for beyond 100-Gb/s IM/DD system.