During the February 2019 Fibre Channel meeting,
different multimode solutions for 128 GFC were
discussed. Based on a straw poll, there was unanimous
support for consideration of the following:
• A true serial 128 GFC variant
• A multi-wavelength variant 56 Gb/s
BiDi solution
• A multi-wavelength variant 56 Gb/s
codirectional (CoDi) solution
One of the most interesting contributions made
in July 2019 was a technical proposal by Finisar, which
suggested that serial 128 GFC could be accomplished
by using VCSELs centered around 940 nm, rather than
the traditional 850 nm.
Meeting the target completion dates and all requirements
per FC-PI-8 MRD will be very challenging; there
are complex technical and market questions that will
need to be resolved.
MMF Developments in IEEE
802.3bs and 802.3cd
In December 2017, references specifying 100 m
reach for 400GBASE-SR16 over OM4/OM5 MMF
were included in IEEE Std 802.3bs™-2017, 200 Gb/s
and 400 Gb/s Ethernet. In December 2018, the same
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100 m references were included in IEEE 802.3cd, 50 Gb/s,
100 Gb/s, and 200 Gb/s Ethernet for 50GBASE-SR,
100GBASE-SR2 and 200GBASE-SR4. The supported
link distance for OM5 is equal to OM4 because all
these links operate only at 850 nm.
IEEE P802.3cm 400 Gb/s over Multimode
Fiber Task Force
The IEEE P802.3cm Task Force met in May 2018
to begin work to “Define a physical layer specification
that supports 400 Gb/s operation over 8 pairs of MMF
with lengths up to at least 100 m.” Additionally, the
Task Force is to “Define a physical layer specification
that supports 400 Gb/s operation over 4 pairs of MMF
with lengths up to at least 100 m.”
This was based on the work of the IEEE 802.3
Next-generation 200 Gb/s and 400 Gb/s MMF Study
Group, which established the need for next generation
multimode 400 Gb/s solutions. These solutions
were designed to leverage recent technology
advancements, including:
• Multiple wavelengths on MMF, first commercially
introduced in 2013 in 40 Gb BiDi modules
• VCSELs supporting 50 Gb/s 4-level pulse amplitude
modulation (PAM4) signaling, while leveraging
the historical multimode/VCSEL link advantages
that include:
�� Relaxed alignment tolerances
(~10x) for lasers, multiplexers/
demultiplexers, and connectors
�� Greater resiliency to dirt
�� Lower drive currents
(5-10 milliamps mA
vs. 50-60 mA)
�� On-wafer testing
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