Demonstration of C-band 112G PAM-4 transmission over 80-km stand-single mode fiber based on direct-detection

In this paper, we experimentally demonstrate the intensity modulation and direct-detection (IM/DD) 112-Gb/s single carrier pulse amplitude modulation (PAM)-4 transmission system over 80-km standard signal-mode fiber (SSMF) without any optical chromatic dispersion (CD) compensation at the 3.8×10−3 BER threshold for 7% the hard-decision forward error correction (HD-FEC). The training based pre-equalization (pre-EQ) and the nonlinear look-up-table (LUT) based pre-distortion (pre-DT) in the transmitter (Tx)-side are employed to reduce the computation complexity and deal with the modulation bandwidth and the nonlinearity impairments of electro-optical modulators and detectors. On the other hand, the system without optical CD compensation modules is obviously more simple and flexible. Therefore, the nonlinear LUT pre-DT simultaneously used for CD compensation will further simplify the system. The BER is about 20% without any digital signal processing (DSP) such as equalization, pre-distortion, pre-equalization or compensation. After signal recovery, the BERs of BTB and 80-km SSMF system can achieve 3.07×10−5 and 1.50×10−3 respectively. The principle of the LUT based pre-DT and the pre-EQ are introduced in the paper.