To deliver the higher HSE port density for 40GbE interfaces, fan-out (breakout or harness) cabling technology is introduced here which also meets the need to keep costs at a manageable level.

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Fiberstore (FS.COM) | Fan-out Technology Used in 40GbE Deployment
Obvious is the growing need for bandwidth required to accommodate various cloud services,
smooth multimedia downloads or uploads, video streaming, as well as growing wireless usage.
10Gbps links are not sufficient enough to handle the increased bandwidth. As such, it’s imperative
to deploy Higher Speed Ethernet (HSE) network, say 40GbE, by using devices that scale to match
customer demands. Besides adding more devices and cables, higher port density is also the ideal
solution to get greater bandwidth. To deliver the higher HSE port density for 40GbE interfaces,
fan-out (breakout or harness) cabling technology is introduced here which also meets the need to
keep costs at a manageable level.
Fan-out Technology Basics
Being one of the latest enabling technologies to help increase port densities and lower costs,
fan-out technology is easy to be grasped. At first sight, a fan-out cable looks very simple. It takes
one (large bandwidth) physical interface and breaks it out into several (smaller bandwidth)
interfaces. A typical example of this is QSFP to SFP+ cable assembly which takes one 40G QSFP
interface on one end and uses a fan-out cable to break it into four SFP+ interfaces one the other end.
In this QSFP+ assembly, a fan-out cable enables splitting out the 4 lanes into Tx/Tx pairs usable for
10GE transmissions.
However, the truth is not definitely just as its face. This complex fan-out technology is critically
important in the distribution layer of 40G data center. The following passages discuss two fan-out
assemblies that are widely used in 40G data center.
40G MPO/MTP Fan-out Cables
Here goes to the MPO/MTP fan-out cables in 40GbE transmission firstly. A MPO/MTP fanout cable is
a multi-fiber optical cable that contains several individual tight buffered optical fibers with one end
terminated with a male/female MPO connector and the other end usually terminated with several
LC connectors. Existing 40Gbps transmission over this multi-mode backbones is accomplished by
using an LC to MPO fan-out assembly to connect the existing LC connectors in the installed cabling
to the MPO connector in the 40Gbps.
Fan-out Technology
Used in 40GbE
Deployment

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Fiberstore (FS.COM) | Fan-out Technology Used in 40GbE Deployment
There are many MPO fan-out cable types. For 40G cabling, the most common breakout cable type is
the one which is able to fan out into 12 fibers. (a typical 12-fiber MPO breakout cable often with
OM3 optical fiber as the transmission media is shown below). This 12-fiber MPO fan-out cable is
terminated with 6 duplex LC connectors on one end and a male MPO connector on the other end,
which can work from MPO trunk backbone assemblies to LC fiber rack system in high density
backbone cabling from 40G device to 10G devices.
40G Direct Attach Fan-out Cables
Direct attach cable (DAC), as a kind of optical transceiver assembly, is also available in fan-out design.
It’s a form of high speed cable with “transceivers” on either end used to connect switches to routers
or servers. Although the “transceivers” on both ends of DACs are not real optics and their
components are without optical lasers, they perform the similar functions as the real transceivers.

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Fiberstore (FS.COM) | Fan-out Technology Used in 40GbE Deployment
DAC fan-out cables can be divided into direct attach copper breakout cables and active optic fan-out
cables.
Converting one form factor to a different form factor is necessary in many cases. For example, a 40G
device may be connected to one or several 10G devices for distribution or adapting. With fan-out
DAC, this process would be much easier. This pre-terminated components can also increase the
reliability of data center effectively.
Fan-out Technology Consideration
One important consideration for fan-out technology is that for each group of fan-out ports, there
must also be a MAC (media access control) engine and the entire IEEE reconciliation layers behind it.
For example, a 40GE QSFP port in fan-out to 4x10GE links must have four individual 10GE MACs
running behind each group of electrical lanes. The port electronics must be able to switch from a
single 40GbE MAC to 4 10GbE MACs, and back again to a single 40GE MAC. This process is integral
in assuring that the lanes have a correct and trackable MAC assignment -- it is crucial to make
fan-out technology actually work.
Conclusion
40G fan-out technology separates a single physical interface into multiple physical interfaces that
are 410GbE-capable, providing high-density interfaces over multiple speeds. This increases interface
flexibility at lower costs. Fiberstore offers a wide selection of fan-out MPO and DAC cables (QSFP to
SFP+ cable) for your 40G transmission. Besides these 40G cables, 40G modules which are fully
compatible with major brands can also be found, such as Cisco QSFP-40G-SR-BD. This compatible
module just costs you US$ 300.00 at Fiberstore, but when you search it on Amazon or somewhere
else, it seems that you have to pay more than US$ 400.00 for a new one.

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Fiberstore (FS.COM) | Fan-out Technology Used in 40GbE Deployment
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Notice: This document is for informational purposes only and does not set forth any warranty, expressed or
implied, concerning any equipment, equipment features, or service offered or to be offered by Fiberstore.
Fiberstore reserves the right to make changes to this document at any time, without notice, and assumes no
responsibility for its use. This information document describes features that may not be currently available.
Contact a Fiberstore sales team for information on feature and product availability.
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