R&M Data Center Handbook

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According to the graphic (page 121, red line) a maximum attenuation of 1.5 dB is available for four plug
connections. By using the new multimode grades, we get a maximum attenuation of 1.2 dB with a certainty of
99.9994% for two MPO grade C M connectors and two LC grade B M connectors, or a maximum 0.7 dB with a
certainty of 93.75%. The maximum target length of 300 m can therefore be achieved without a problem.
In this way, users also gain freedom and security in planning in multimode as well. If more connections are
required, one just selects connectors from a higher quality class. The previous practice of using maximum values
leads to incorrect specifications. The median, or 95% value, should be used in the planning process instead.
As already required with single mode grades, multimode grades also require each-to-each guaranteed values (i.e.
where connectors are measured against connectors). Information taken from measurements against a reference
connector – a normal procedure with competitors – are not helpful, but instead lead to pseudo-security in the
planning process. To be able to plan a future-proof network and to cope with the diminishing attenuation budgets,
a reliable classification system by means of grades for single and multimode components is crucial.
Connector Types
The LC and MPO connector were defined for data center applications in accordance with ISO/IEC 24764, EN 50173-5
and TIA-942 standards for fiber optic cabling systems.
MPO (IEC 61754-7)
LC Connector (IEC 61754-20)
The MPO (Multi Patch Push-on) is based on a plastic ferrule that allows of up to 24
fibers to be housed in one connector. In the meantime, connectors with up to 72 fibers
are already in development.
This connector stands out for its compact design and easy operation, but brings disadvantages
in optical performance and reliability.
This connector is of crucial importance because of its increased packing density and
ability to migrate to 40/100 gigabit Ethernet.
This connector is part of a new generation of compact
connectors. It was developed by Lucent (LC stands for Lucent
Connector). Its design is based on a 1.25 mm-diameter ferrule.
The duplex coupling matches the size of an SC coupling. As a
result, it can achieve extremely high packing densities, which
makes the connector attractive for use in data centers.
Other common connector types, sorted by IEC 61754-x, include:
ST Connector (also called BFOC, IEC 61754-2)
These connectors, with a bayonet locking mechanism, were the
first PC connectors (1996). Thanks to the bayonet lock and
extremely robust design, these connectors can still be found in
LAN networks around the world (primarily in industry). ST designates
a “straight” type.
DIN/LSA (optical fiber plug connector, version A, IEC 61754-3, DIN 47256)
Compact connector with screw lock, only known in the German-speaking world.
SC Connector (IEC 61751-4)
This connector type with its square design and push/pull system
is recommended for new installations (SC stands for Square
Connector or Subscriber Connector). It makes high packing
density possible because of its compact design, and can be
combined into duplex and multiple connections. Despite its age,
the SC continues to gain in importance because of its outstanding
properties. Up to this day, it remains the most important WAN
connector worldwide, usually as a duplex version, due to its good optical properties.
Page 122 of 156 © 08/2011 Reichle & De-Massari AG R&M Data Center Handbook V2.0