Designing a data center has always been a challenge. These days the
technology that we use to power and cool the data center is much better than
previous generations. But because the compute and storage networks are evolving
so quickly, it’s difficult to predict the network infrastructure required to
sustain the rapid growth in speed/capacity that will be needed over the next
few years. And when things change, you need the assurance that everything will
TIA 942 A standard offers guidance on the implementation of
structured cabling systems that provide for scale, agility and availability of data
center networks. The reasons to avoid point-to-point network topologies are
well-known to infrastructure designers – network engineers aren’t always aware
of the disadvantages with that standardization and structure. Certainly the
operations team can point to the ongoing cost and risk that quickly mounts when
these design rules are not followed. But the network wants what the network
wants – speed! The budget demands restraint, and the operations team wants
To answer the question, “What is the best network infrastructure to
deploy?” there are some tools that will help. The objective of the physical
network design is simply to support the best network alternative both now and
in the future. Understanding the alternatives that are available – multimode
and singlemode optics – duplex or parallel fiber paths – will certainly help
ensure that the speed is available at an optimal cost. Before you move forward,
you need to ask these questions:
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Engineering optic links consider various signal impairments
and insertion and provide a specific optic power budget and physical link to
support the optic application. The design can then be expressed as a practical
topology (number of connections) and total link length for a given optic
application. Focusing on all parts of the power budget provides a complete
guaranteed channel design. Accounting for the entire loss budget including inter-symbol
interference (ISI) and channel insertion loss provides solid guaranteed
ISI is caused by the interaction of the optical signal with the fiber
media. ISI is a measure of signal
impairment or, in other words, an increase in the noise level in
the signal. The minimum received power requirement must be increased to maintain
the required signal to noise ratio that will meet the target bit error rate. Figure
1 10GbE shows this imparement as 3.02db. Other optic applications will have
different optical power budgets that are adjusted to compensate for these
signal impairments as they change in value due to increased speeds for example.
Operating with multiple wavelengths increases data center capacity
OM5 fiber supports higher bandwidth at longer wavelengths. This
additional bandwidth is being used to carry multiple optical signals/channels
on the same pair of fibers. When this capability is combined with new optical
modules the result is a higher capacity link that maintains the lower cost of a
duplex fiber physical infrastructure.
Standardized OM5 cable enables optic module manufacturers to guarantee the
reach of these wavelength division multiplexed technologies (WDM). For instance
SWDM4 100G extends the supported reach least 50 percent to 150m (see graph above).
Combining SWDM4 or BiDi technology with duplex cabling can provide a
significant cost saving when migrating to higher speed, switch to switch links.
As a result they are fast becoming the common choice for these applications.
There’s a lot to think about. In part two, I’ll explore how to determine
lowest link cost and how the CommScope Application Assurance combines all new
technologies into an engineered guaranteed link design.