The 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, although there are
differences in various countries. TIA-568 has been under continual
revision since its inception. The current version is "568 C". It
includes some major changes from earlier versions for fiber optics as it
adopts sections of IEC standards for international standardization.
Work is always ongoing in TIA 568. Several
new issues have been addressed including passive optical LANs based on
FTTH PONs and polarity of array fiber connection systems that now
occupies half the standard itself, an indication of the complexity of
the topic. The high component losses allowed, especially connector loss
at 0.75dB, has not been addressed. There is widespread knowledge of this
problem but manufacturers have been reluctant to change the standard due
to the tighter controls on products they produce.
568 B3 added 50/125 fiber as an acceptable
type and specifies the performance of cabled fiber as follows:
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3500 (OM4) |
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Note that these specs are quite
conservative, compared to what is routinely available in the
marketplace. 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.
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. The latest versions of the document use
LC connectors as the example, replacing SCs.
Color Codes: Multimode connectors are beige
for 62.5/125 OM1 fiber, black for 50/125 OM2 fiber, aqua for
laser-optimized 50/125 OM3 and OM4 fiber and lime green for wideband OM5
fiber. Singlemode connectors
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! Polarity for multipin
connectors (MTP/MPO) are specified in several different versions and are
very confusing, requiring about half the total number of pages in the
document.
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 (Connection Loss):
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Notes:
These connection
losses are for a fiber terminated in a connector mated to a known good
reference connector per FOTP-34 or FOTP-171.
Remember these
connector losses are maximum values. The loss is high to allow
prepolished/splice connectors which have higher loss than
adhesive/polish connectors because the connectors include both a
connection loss and a splice loss.
The high loss also
covers array connectors like MPOs which have higher loss due to the
alignment of a large numbers of fibers. Users may specify lower loss for
installations if agreed upon by all parties involved.
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.
Recommendation:
For design or loss budget purposes, single fiber adhesive/polish
connectors as found on factory-made patchcords should be less than
0.3dB connection loss. Splice-on connectors using fusion splices or
mechanical splices which include a splice loss in the connector loss
should be less than 0.5dB. The highest loss is reserved for some
mechanical splice-on connectors and array fiber connectors.
Splices
Fusion or mechanical splices shall not have a loss of more than 0.3 dB for either multimode or singlemode fiber. 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) 2021 The Fiber Optic Association, Inc.