Demonstration of 100Gbaud DSM Signal Transmission in C-Band IM/DD System

We present a low-cost intensity-modulated direct detection (IM/DD) system for the transmission of high-order Quadrature Amplitude Modulation (QAM) signals. By adopting the 1-bit quantized Delta-sigma modulation (DSM) technology, we quantized the Discrete Multi-Tone modulation (DMT) time-domain waveform carrying the higher-order QAM signal into on-off keying (OOK) signal, and successfully realized the transmission of the higher-order QAM signal on the IM/DD link. Thanks to the high quantization SNR of the DSM modulator, up to 4096QAM transmission is supported. In particular, through the use of Vestigial Side Band (VSB) and pre-equalization, we experimentally demonstrated the transmission of 100G baud DSM-OOK signal in C-band 50 km fiber. The experimental results show that the bit error ratio (BER) of the 1024QAM signal can reach the hard decision forward error correction (HD-FEC) threshold
$3.8 \times 10^{-3}$
, and the BER of the 4096QAM signal can reach the soft decision forward error correction (SD-FEC) threshold
$4.2 \times 10^{-2}$
. To our knowledge, this is the first experimental demonstration of high-speed DSM signal transmission on optical fiber links.