OFC 2021 Rump Session, Wednesday, 09 June 06:00 – 08:00 am PDT
Did the Optics Industry Blunder by Switching Intra-Datacenter Links from NRZ to PAM4?
Will More DSP like PAM6 and Coherent Follow, or Will WDM and Parallel Save the Day?
Session Organizer and WDM Team Captain: Chris Cole, II-VI Incorporated, USA
WDM Team Provocateurs: Shigeru Kanazawa, NTT, Japan; Boris Murmann, Stanford University, USA: Chris Pfistner, Avicena Tech, USA; Peter Winzer, Nubis Communications, USA
Session Organizer and DSP Team Captain: Ilya Lyubomirsky, Marvell, USA
DSP Team Provocateurs: Yi Cai, ZTE, USA; Dan Sadot, Ben Gurion University, Israel; Henry Sun, Infinera, Canada; Xiang Zhou,Google, USA
Description from WDM Team:
PAM4 was chosen for bandwidth limited electrical channels by the IEEE Ethernet Group in 2012. Modulation format for 50G λs was debated by the IEEE in 2015. Shannon provided clear guidance to stick with NRZ because the optical channel is limited by SNR and not bandwidth. Unfortunately, because the optics industry is the tail on the IC industry dog, PAM4 was chosen to reuse ASIC SerDes technology already in development. This unnecessarily and permanently locked in lower SNR and higher power for optical links. PAM4 50G λs will ship in the millions despite availability of mature 50GBaud technology which enables 50G NRZ λs. Shannon was again ignored by the IEEE for 100G λs and appears likely to be ignored for 200G λs. However, emerging applications not tied to Ethernet are returning to communication theory fundamentals and defining higher channel count lower-order modulation WDM and Parallel links.