2019 年 E102.C 巻 4 号 p. 316-323
The needs for ultra-high speed short- to medium-reach optical fiber links beyond 100-Gbit/s is becoming larger and larger especially for intra and inter-data center applications. In recent intensity-modulated/direct-detection (IM/DD) high-speed optical transceivers with the channel bit rate of 50 and/or 100 Gbit/s, multilevel pulse amplitude modulation (PAM) is finally adopted to lower the signaling speed. To further increase the transmission capacity for the next-generation optical transceivers, various signaling techniques have been studied, especially thanks to advanced digital signal processing (DSP). In this paper, we review various signaling technologies proposed so far for short-to-medium reach applications.