At the March 7, 2018 IEEE 802.3 meeting, the Next-Gen Multimode 200 and 400 Gb/s study group voted down physical layer specification that supports 200 Gb/s operation over one pair of multimode fiber. This was the second time the proposal was voted down. The specification would have included duplex OM3, OM4, and the potential for OM5, which supports shortwave wavelength division multiplexing (SWDM). The failed motion raises further questions about the viability or benefit of OM5 for current or future applications.
One major roadblock facing OM5: SWDM technology cannot be easily broken out at the servers, limiting it to switch-to-switch topology. Yet most installed multimode fiber links in data centers — almost 50% according to Leviton data — use breakout cables at switch to server. This severely limits the broad market potential for 200 Gb/s over duplex multimode.
Here is a summary of current and planned 200 Gb/s options:
|IEEE Application||Standard||Fiber||Number of fibers||Reach|
As OM5 appears to offer almost no benefit over OM4, and with the growing feasibility of single-mode options, OM5 is likely to become the “Cat 4” of the fiber generations: skipped over and forgotten.
You can learn more about cabling options for 200 Gb/s, 400 Gb/s and beyond in the Leviton white paper "Navigating Cabling Options for Enterprise and Cloud Data Centers."