The Fiber Optic Association - Tech Topics
EAI/TIA
568 For Fiber Optics
The EAI/TIA
568 standard for premises
cabling is used by most manufacturers and users of premises cabling
systems in the US. Internationally, IEC/ISO 11801 is very similar for
fiber optics, although there are differences in various countries.
TIA-568 has been under continual revision since its inception.
The current version is "568 B.3" covering fiber optics.
It includes some major changes from earlier versions for fiber
optics. TIA
568 "C" is expected to be published sometime in 2008, but fiber optic cabling changes are not
substantial. These include:
Fiber Optic Cable Performance Standards
568 B3 adds
50/125 fiber as an
acceptable type and specifies the performance of cabled fiber
as follows:
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Note that
these specs are quite
conservative, compared to what is routinely available in the
marketplace,
especially now that more fiber manufacturers are offering high
bandwidth 62.5/125 fiber and 50/125 fiber with even higher bandwidth
than OM3 (currently being called OM3+ by most manufacturers, but an OM4
spec with 850 nm BW of approximately 3500 MHz-km.) The spec notes also
that the cable manufacturer
can use the fiber manufacturer's data on bandwidth, so they do
not have to test it.
Hybrid Cables
The standard
notes that hybrid
cables are permitted, with markings per ANSI/EIA/TIA-598-A. (
Hybrid cables contain both multimode and singlemode fibers.)
Premises Cables
Horizontal cables with 2-4 fibers require a 25 mm bend radius after installation or 50 mm while being pulled with a tension of 50 pounds (222 N).
Other
premises cables require
a bend radius of 10 times the cable outside diameter unloaded
and 15 times the OD when under the maximum rated pulling tension
for that cable.
Outside Plant Cables
The standard calls for water-blocked cables with a minimum pulling tension of 600 pounds (2670 N).
Minimum bend radius is 20 times the cable diameter under max rated pulling tension and 10 times unloaded.
Drop Cables
The standard
adds a definition
for "drop cables," low fiber count cables used to connect
high fiber count cables to smaller fiber count cables or patchcords
in a single location. These cables must withstand 300 pounds pulling
tension (1335 N).
Connectors
and Connecting Hardware
Any connector
design is permitted
as long as it has a FOCIS document (Fiber Optic Connector
Intermateability
Standard). All small
form factor connectors with FOCIS
documents are acceptable.
Color Codes:
Multimode connectors
are beige for 62.5/125 fiber, black for 50/125 fiber, singlemode are
blue, angle-polished singlemode are green, and outlets are also color
coded
accordingly. Cable color codes are the same as TIA-598.
Duplex connectors are keyed and are always crossover - that is Position A of one connector connects to Position B on the other end! Patchcords have this feature too, to permit correct connection of transmitters and receivers!
Outlet boxes
must have provision
for termination of at least 2 fibers.
Patch panels
and outlets must
provide unique identification for the connecting cabling.
Connector
Mating Loss:
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Remember these connector losses are maximum values. The loss is high to allow prepolished/splice connectors which have higher loss than adhesive/polish connectors. Users may specify lower loss for installations if agreed upon by all parties involved.
Notes:
Loss is tested per FOTP-171, single cable reference.
Maximum loss
spec holds over temperature
(0-60C), humidity (95% @ 40C), impact, pull strength of coupling
(7.4 lb./33N), durability (500 matings), cable retention (11 lbs./50
N straight, 4 lbs./19N at 90)flex and twist.
Splices
Fusion or mechanical splices shall not have a loss of more than 0.3 dB. Multimode splices must have a return loss of better than 20 dB. Singlemode splices must be better than 26 dB ORL for general applications, 55 dB ORL for CATV broadband analog video.
(C) 2004-8 The Fiber Optic Association, Inc.
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