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Meanwhile the development of 40- and 100-Gbit Ethernet was
shaping up to shorten the distances OM3 could achieve, akin to
but not quite as dramatic as the shorter distances to which OM1
and OM2 can support 10G. The need for a higher-performance,
longer-reaching multimode fiber ultimately resulted in the specification of OM4.
When the TIA approved its OM4 fiber specification in 2009,
CommScope’s Paul Kolesar explained in an article we published,
“Not everyone could wait for the new OM4 standard to emerge.
Early adopters have been enjoying OM4 capability for more than
five years. By the time the TIA committees were voting on the
new OM4 specifications, hundreds of data centers around the
world were already running smoothly with next-generation, OM3-
exceeding fiber cabling that would later meet OM4 standards—
most of which had been installed years ahead of time … Some of
the same laser-optimized fiber cables that exceeded OM3 standards now meet TIA’s OM4 standard. The OM4 standard adopted
the most-stringent of the proposals that were submitted for consideration, so cables that adhere only to less-stringent specifications cannot claim compliance.” (“OM4 fiber cabling standard for
next-generation data centers,” October 2009)
OM4’s minimum EMB at 850 nm is 4,700 MHz.km, and its minimum OFL bandwidth at 850 nm is 3,500 MHz.km. Like OM1, OM2,
and OM3, it has a minimum OFL bandwidth of 500 MHz.km at 1300
nm. OM4 supports 40GBase-SR4 and 100GBase-SR10 to 150 meters;
OM3 supports both to 100 meters.
While this article addresses optical fiber, the importance of
connectivity in high-speed links cannot be ignored. In an optical link of any distance, the fiber will contribute some signal loss;
points of connectivity in those links are more-significant contributors of loss. The ability to extend transmission distance at a
given speed (e.g. 10 Gbits/sec) is enabled by decreasing connection
losses. Nonetheless, the optical fiber plays a significant role in accepting and carrying optical communications’ light pulses, and
the information in this article details them.
Multiple wavelength capability
Over the past approximately 18 months another multimode fiber
type has emerged and advanced significantly toward official standard specification. Dubbed wideband multimode fiber (WBMMF),
the medium is being referred to by some as “OM4+” reminiscent
of the decade-earlier “OM3+.” However, the differences between
WBMMF and OM4 are more significant than those between OM4
and OM3. Specifically, WBMMF is being developed to support optical transmission at multiple operating windows through what is
known as wave-division multiplexing (WDM). Whereas the 850-
nm window has been primary, and OM3 as well as OM4 fibers
are bandwidth-optimized to support transmission within that