A few months ago, I needed to quickly come up to speed on 100G and 400G optics, so I worked on a cheat-sheet for myself. With the variety of multiplexing techniques and encoding schemes used, there’s a bit more to keep track of than with 10G and 40G optics.

The faster speeds couldn’t be achieved with the same approach as 10G optics. These optics all use either more channels (signals on more strands with MPO cabling, or more signals on the same strand with integrated WDM), or more advanced encoding schemes (like PAM-4 instead of NRZ). Most of these options also are single-mode based.

I’ve posted my table below with notes on some of the more common 100G and 400G optics in hopes that it might help others. I’m specifically not including 400G ZR / ZR+ optics. These will likely have a big impact on the industry in the coming years, but the characteristics can vary quite a bit from vendor to vendor, so it’s hard to summarize in a simple table.

It’s also worth noting that particularly with 400G optics, power and thermal limitations start to become a significant limiting factor.

100G + 400G Optic Cheat Sheet

Name Electrical Interface Power Fiber Connector Distance Qty of Strands Used Channels per Strand Optical Signal Modulation FEC Notes
100G SR4 QSFP28 (4x25) 3.5W OM3+ MPO 70m 2x4 1 25G NRZ Optional
100G LR4 QSFP28 (4x25) 4.5W SMF LC 10km 2 4 25G NRZ Optional
100G CWDM4 QSFP28 (4x25) 3.5W SMF LC 2km 2 4 25G NRZ Yes
100G DR1 QSFP28 (4x25) 4.5W SMF LC 500m 2 1 100G PAM-4 Yes Interop w/ 400G DR4 breakout
100G LR1 QSFP28 (4x25) 4.5W SMF LC 10km 2 1 100G PAM-4 Yes Interop w/ 400G PLR4 breakout
400G DR4 QSFPDD (8x50) ~10W SMF MPO 500m 2x4 1 100G PAM-4 Yes APC fiber only. Breakout to 4x100G DR1
400G LR4 QSFPDD (8x50) ~12W SMF LC 10km 2 4 100G PAM-4 Yes
400G FR4 QSFPDD (8x50) ~12W SMF LC 2km 2 4 100G PAM-4 Yes
400G SR8 QSFPDD (8x50) ~10W OM3+ MPO-16 70m 2x8 1 50G PAM-4 Yes
400G PLR4 QSFPDD (8x50) ~10W SMF MPO 10km 2x4 1 100G PAM-4 Yes Breakout to 4x100G LR1