IM/DD-Based 112-Gb/s/lambda PAM-4 Transmission Using 18-Gbps DML

Single-channel 112-Gb/s PAM-4 transmission based on low-cost intensity modulation and direct detection (IM/DD) optics is experimentally demonstrated over 1-km standard single-mode fiber. By employing a digital precompensation, duobinary encode/decoding with PAM-4 signal and 7-level training-sequence-aided least mean square (TS-LMS) algorithm, we successfully achieve a receiver sensitivity of about -2 dBm with 7% overhead HD-FEC. Chirp management is applied at the transmitter side to extend the reach to 1 km for transmission at 1500 nm. This is the first demonstration, to the best of our knowledge, that 112-Gb/s PAM-4 modulation is achieved using only a 18-GHz (3-dB-bandwidth) commercial directly modulated laser. The method proposed in this paper is both bandwidth and computationally efficient, which is thought to be feasible in the low-cost short-reach optical applications.