Optical fiber receives a boost
Addendum contains important new information in support of higher bandwidth optical fiber applications.
July 1, 2012
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Optical fiber cabling is undergoing significant changes in the industry to meet the demands of newer, higher bandwidth, applications.
Some of these changes relate to the performance of the fiber itself, for example the introduction of a higher bandwidth OM4 multimode fiber in the market. Others relate to establishing more controlled test procedures to verify optical fiber installations in the field.
This is particularly important for newer applications that impose very tight optical loss budgets.
For this month’s column, I wanted to present to you some of the changes and additions that are included in a new Addendum 2 to TIA-568-C.0 Standard on “Generic Telecommunications Cabling for Customer Premises”. TIA-568-C.0-2 Addendum updates the optical fiber test procedures for multimode fiber and includes new information in Annex B on array polarity systems and in Annex D on optical fiber applications.
Optical Fiber Testing: One of the most significant changes in TIA-568-C.0-2 is that field test instruments for multimode fiber cabling are now required to meet TIA-526-14-B Standard on “Optical Power Loss Measurements of Installed Multimode Fiber Cable Plant.”
I wrote about the TIA-526-14-B standard in the May/June 2012 Standards Update column. In essence, TIA-526-14-B requires that the light coming from the end of the launch cord meet the “encircled flux” launch conditions and replaces the previous TIA-526-14-A standard, which uses an external mandrel wrap with a Category 1 light source.
It should be noted that the launch conditions specified in TIA-526-14-B also apply for Optical Time Domain Reflectometer (OTDR) testing. These launch conditions can be achieved either within the field test instrument or by the use of an external mode conditioner.
Verifying Launch and Receive cord quality: Recognizing that the quality of the test cords and cleanliness of the connector interface can affect measurement accuracy, the TIA 568-C.0-2 addendum specifies that test jumpers (cords) and the ports under test should be clean and free of damage.
The endface condition of both the test jumper and the test port should be verified in accordance with IEC-61300-3-35 and Annex H of TIA-526-14-B for “reference grade” terminations. If higher than expected losses are measured, inspect and clean the connectors per IEC-61300-3-35 and retest. If cords continue to test high, replace the cord with a new one if necessary.
Array Polarity Systems: A large portion of the TIA-568-C.0-2 addendum provides illustrations and descriptions of array polarity systems for supporting multiple duplex systems and for supporting parallel signals. The most significant changes relate to array polarity implementations for parallel signals. Three sample methods are described, Method A, B and C. All these methods achieve the same purpose but are implemented differently. The purpose is to create an optical path from the transmit port of one device to the receive port of another device.
These different implementations may not be interoperable, and the Standard recommends that a method be selected in advance and maintained consistently throughout an installation. It should be noted that TIA 568-C.0-2 Addendum does not specify any polarity method that must be used for compliance. Designers and installers are encouraged to contact their manufacturers to evaluate polarity options.
Optical Fiber application support information: The current TIA-568-C.0 Standard includes a Table of maximum supportable distances and attenuation for optical fiber applications by fiber type. The new TIA-568-C.0-2 Addendum updates this Table for higher bandwidth applications and includes support information for the new OM4 fiber, which was not part of the TIA-568-C.0 Standard when it was published.
Additional support information is also provided for passive optical network (PON) applications over single-mode fiber.
The TIA-568-C.0-2 Addendum contains important new information in support of higher bandwidth optical fiber applications including optical loss testing procedures, array polarity systems and supportable distances. At the time of this writing, the standard has been approved for publication and is expected to be available shortly.
Paul Kish is Director, Systems and Standards at Belden.
The information presented is the author’s view and
is not official TIA correspondence.