Transmission of 112(4×28)-Gb/s PAM-4 Signal over 48.6-km SSMF within only 50-GHz Grid

• A transmission of 112(4×28)-Gb/s PAM-4 signal is experimentally demonstrated within only 50-GHz grid, achieving an optical SE of 2.24 b/s/Hz.
• For IM/DD based PAM-4 transmission, it is the first time to the best of our knowledge that 112-Gb/s PAM-4 signal has been transmitted over 48.6-km SSMF, which is compatible with 50-GHz standard gridding.
• The proposed method is bandwidth and computationally efficient, which is thought feasible in the low-cost short reach optical networks.

In this paper, a transmission of 112(4×28)-Gb/s PAM-4 signal is experimentally demonstrated within only 50-GHz grid, achieving an optical spectral efficiency (SE) of 2.24 b/s/Hz. For the intensity modulation and direct detection (IM/DD) based PAM-4 transmission, it is the first time to the best of our knowledge that 112-Gb/s PAM-4 signal has been transmitted over 48.6-km standard single mode fiber (SSMF), which is compatible with 50-GHz standard gridding. By employing digital pre-equalization, duobinary encoding/decoding and 7-level based training sequence aided least-mean square (TS-LMS) algorithm, each lane of the 28-Gb/s PAM-4 signal occupies less than 11-GHz optical spectral (3-dB bandwidth), resulting in negligible inter-channel interference for the 4-lane 112-Gb/s PAM-4 signals within 50-GHz grid. The proposed method is bandwidth and computationally efficient, which is thought feasible in the low-cost short reach optical networks.