CommScope® Enterprise Data Center Design Guide - Public ...

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Single-mode fiber has much lower attenuation than multimode fiber. TIA/EIA specifies that a
standard grade single-mode fiber operating at 1310 or 1550 nm has a maximum attenuation
of 0.50 dB/km (1.0 dB/km if tight buffered). Again, today’s fibers typically improve upon this
requirement.
40 and 100G for Fiber
Most data centers recently built or under construction today are likely to be using speeds of
10Gb/s initially, but must also be prepared for new technologies and higher speeds in order
to provide an expected lifespan of 15+ years. Similarly, existing data centers planning
upgrades or expansion must also consider the needs for higher speeds.
If anything remains the same, it’s the need for higher and higher data rates over time. 40 and
100 Gigabit Ethernet solutions are available within the standards today and the first commercial
deployments are coming soon. This will require infrastructure that can support these speeds.
Standard optical fibers, like 62.5 μm OM1 and 50 μm OM2, have carried us a long way,
but their limitations are finally being reached. We have seen at speeds of 10 Gb/s, the
distances for OM1 and OM2 are too limited and laser-optimized 50 μm fiber is required for
most applications. It is likely the standards for 40 and 100G will NOT included OM1, OM2
or OM2+ fibers for any distance, no matter how short.
Therefore, when preparing for data rates above 10G, OM3 fiber is the absolute minimum
grade of fiber that should be installed. The draft standard shows a distance of 100 meters
using OM3 for both 40G and 100G Ethernet applications. This distance covers an
overwhelming percentage of data center applications. However, the 100 meter distance is
given as a point to point solution. With typical systems that have 4, 6 or even 8 connector
pairs within a link, that extra loss will shorten the allowable distance.
Extended-range OM3 fibers are available today, with specified distances of 550 meters as a
minimum for 10 gigabit Ethernet performance. These type fibers are now represented within the
Standards and have an OM4 designation. Completed in late 2009, TIA-492AAAD outlines the
requirements for an OM4 fiber that also supports 40 and 100 GbE. The use of OM4 fiber will
allow extended range and/or an increase in the number of connection points for very high data
rate applications. Note that some of the 550 meter rated fibers sold before TIA-492AAAD was
completed may not meet the bandwidth of the requirements and may not be true OM4 fiber.
All CommScope LazrSPEED 550 fiber sold has met the requirements of TIA-492AAAD.
Correct fiber counts will also help eliminate the need to pull new backbone cabling every time
a new application is available. 40 and 100G applications will likely run over “parallel
optics,” which is simply the process of breaking up a high speed data stream over multiple
fibers, sending them over the passive system, and recombining these signals at the end.
Standards organizations (Both United States and international) are looking at various options
utilizing MPO array connectors; a likely scenario for 100 gigabit Ethernet transmission includes
having 10-fibers (of a 12-fiber bundle) act as a transmit channel, and another 10-fibers (also of
a 12-fiber bundle) acting as the receive channel. For the system designer, this means that
having 24 fibers going to many locations within the data center would be a minimum
requirement to ensuring the capability to run parallel optics applications in the future.
At the same time that Ethernet is pushing the limits of data throughput, Fibre Channel is on a
similar track. 8 Gigabit speeds are in wide use today, and speeds of 16 and 32G are being
developed within the standards. To achieve these speeds, a similar approach should be taken
with the choice of optical fiber. Avoid OM1 and OM2, using OM3 fiber as the minimum
grade of glass throughout the system and strongly consider the use of OM4 fiber to allow for
added distance and/or connector pairs within a link.
For optical fiber with a higher bandwidth to transmit at these high data rates, specify singlemode
fiber. The cost associated with single-mode fiber electronics will likely continue to be
twice that of multimode, and therefore not the best choice for the distances seen in the average
data center. However, single-mode fiber is a great option for connecting data centers, for
unusually long runs or future-proofing. There will be single-mode options within the standards for
40 and 100G and some data centers can make use of its high bandwidth.