28-Gbaud PAM4 and 56-Gb/s NRZ Performance Comparison Using 1310-nm Al-BH DFB Laser Matsui, Yasuhiro ; Pham, Thang ; Sudo, Tsurugi ; Carey, Glen ; Young, Bruce ; Xu, Jack ; Cole, Chris ; Roxlo, Charles Abstract Publication: Journal of Lightwave Technology Pub Date: June 2016 DOI: 10.1109/JLT.2016.2542579 Bibcode: 2016JLwT...34.2677M