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Wire & Cable ASIA – September/October 2007 55
Wir & Cable ASIA – March/April 13
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It is worth noting that new measurements should
include the very long wavelength of 1,625nm. These new
measurements would propose additional qualifications for
that wavelength where the microbend edge moves in as
the fibre is strained.
Although this is a requirement of some customers in their
own standards, it is not part of the existing generic fibre
standards.
Cable shrinkage testing needs to move to a higher level
of repeatability and gauges for this purpose have been
designed. The range of testing and the effect of fibre
extrusion from the cable core need to be determined as
well. This is only a secondary effect of GR 326 the test
standard for cable connectors and cable assemblies.
Conclusions
The introduction of reduced bend radius fibres, and
their emerging popularity in fibre-to-the-premise (FTTP)
architectures, is cause for concern when it comes to the
current GR-409, GR-20, GR 326 and other specification
standards written for conventional fibres. New tests
should be proposed to accurately define their unique
characteristics to better ensure long-term reliability.
A cable design that takes advantage of the tighter bend
radius fibre would most certainly show much higher
attenuation using conventional single mode fibre. In other
words, a reduced bend radius fibre would survive very well
in an environment where conventional fibre would not.
The cable to connector interface may create new aging
models where cable shrinkage can lead to unacceptable
fibre bend radii at the cable/connector interface.
The results of which will only show up after loose cable
assemblies are aged and then moved. This alone
indicates the need for a set of revised test standards and
requirements for reduced bend radius types of fibre.
Cable designs tested to GR-409 or GR-20 are
requirements for GR 326 testing. The need exists to use
fibre strain and cable shrinkage as well as fibre extrusion
from cables after aging as a more complete precursor to
GR 326 testing.
Also with increased environmental operating ranges
of cables becoming the norm, thermal co-efficient of
linear expansion values need to be incorporated into
specification performance precursor requirements.
This paper proposes to update existing standards,
particularly the GR-409 specifications for required
tolerance for shrinkage and fibre strain. Otherwise, it
is possible for sub-par cable designs to pass existing
standards as they are written and be deployed in the field.
It should be recognised that conventional fibre and
reduced bend radius fibre exhibit different properties
and characteristics, and test criteria should be written to
address the requirements of both. Therefore, the proposal
is to consider adding more focused test criteria to existing
standards specifications. This in effect creating a new
class of GGR-409 and GGR-20 qualifications specifically
identifying the fibres used and qualified in any specific
cable designs.
Re-purposing the current standards with new reduced
bend radius fibres in mind will enable service providers
to take full advantage of the unique characteristics these
fibres bring to the table, particularly in today’s FTTP
deployments.
Acknowledgments
The author would like to acknowledge the help of Wagner
Aguiar, Ken Nardone, Henry Rice, and Bill Jacobsen in
obtaining data and test information for this paper.
References
TIA-455A Fiber Optic test procedures
Telcordia GR-220-core Issue 3
Telcordia GR-4409-core issue 22
Telcordia GR-3326-core issue 44
ITU 652 .A-D 22009-11
ITU 657.A 200 9-11
Reliability of bend Insensitive Fibres; Willem Griffoem Draka
Communications Proceedings of the 58th IWCS pages 251- 257 2009
Macrobending Loss in Bend Insensitive Fibres: A Statistical Parameter?
Susanna Cattelan, Prysmian SpA, Proceedings of the 58th IWCS pages
258-263