8/3/2019 Best Practices Fluke
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White Paper
Table of contents
Why you should care 2
How it works 2
Loss-length testing procedures 2
Additional fber best practice resources 2
Introduction to fber best practices
The Fiber Best Practice Series was designed by Fluke
Networks to educate about important optical fber
best practices, including:
Fiber inspection and cleaning
Loss-length (Tier 1) fber certifcation
Fiber plant characterization and troubleshooting
(Tier 2 certifcation)
This white paper details the best practice o fber
plant characterization and troubleshooting
(Tier 2 certifcation).
With 40 G/100 G inrastructure deployments in the
datacenter quickly becoming reality, the shrinking
loss budgets o optical fber cabling due to increasing
bandwidth demands mean that reliable and efcient
initial installations are now more important than
ever. To minimize costly installer or contractor
callbacks, network technician troubleshooting time,
and unnecessary network downtimes, fber-handling
best practices should always be ollowed.
Fiber Best Practice:
Fiber Plant Characterization and
Troubleshooting (Tier 2 Certifcation)
8/3/2019 Best Practices Fluke
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White Paper
Fluke Networks www.flukenetworks.com2
N E T W O R K S U P E R V I S I O N
Fluke NetworksP.O. Box 777, Eve rett, WA USA 98206-0777
Fluke Networks operates in more than 50 countriesworldwide. To
nd your local oce contact details,go to
www.fukenetworks.com/contact .
2010 Fluke Corporation. All rights reserved.Printed in U.S.A.
2/2010 3672932A D-ENG-N
Why you should care
In gaining ull visibility into the ber plants attenuation,
insertion loss, and refectance at connectors, splice locations, and
unantici-
pated loss events, an optical time domain refectometer (OTDR)
provides valuable insight into a ber installation that cannot be
obtained
rom an optical loss test set (OLTS). Such an ability to pinpoint
events is critical or troubleshooting and rooting out potential
cabling
component problems in the ber plant to prevent or minimize
costly network downtime. Although currently considered a
complementary
test by industry standards such as Telecommunication Industry
Associations (TIA) TIA-568-C.0 and International Organization
or
Standardizations (ISO) ISO 14763-3, it has long been considered
a best practice by ber experts.
How it works
An OTDR iners loss, refectance, and locations o events by
shooting pulses o light into
one end o a ber link and using a photodetector to sense
refections rom loss-causing
incidents such as connectors, splices, and bends. These
incidents are oten reerred to
as events - some o which are expected and others, unexpected.
When a pulse o light
travels down the ber, most o it continues in the direction o the
ber. However, due to
the inherent composition o the glass ber, a small raction o the
light, called backscat-
ter, is dispersed in dierent directions. Some o this backscatter
makes its way back to
the sensitive detectors at the OTDR source, which is analyzed
beore being graphicallydisplayed to depict the link-under-test.
Such a characterization o the ber link is called
a trace, and plots the measured refectance and loss over time.
See Figure 1 or an
example. Legacy OTDRs used to require years o technical
experience in order to read
and interpret traces; however, the majority o present-day OTDRs
contain comprehensive
sotware that automate trace analysis and test parameter set-up,
among other advanced
analytical capabilities (see Figure 2).
Fiber plant characterization and troubleshooting procedures
Connect 1 the OTDR to one end o the ber link-under-test.
Congure or select the appropriate limits to test against.
Shoot a trace o the ber link-under-test.
Review the testing results or any passes or ailures. Results are
typically
conveyed in a graphical plot or event chart ormat. As shown in
Figure 1, the OTDR
trace should decrease gradually rom let to right because o loss
rom scattering and events such as connections and splices.
Refections, in the orm o spikes on the trace, can be caused by
breaks, cracks, splices, connections, and sharp bends.
Compare to the limits being tested against to ensure that the
component measurements are within the specied limits. Certain
events such as splices, connectors, and the end o the ber are
expected on OTDR traces and thus actored into overall loss
budgets. However, their loss must still conorm to specications,
whether they are industry standards or determined by the
user. Based on the guidelines being compared to, OTDRs can
return PASS or FAIL results or each event.
1 Similar to using test reerence cords when using an OLTS,
ensure a launch ber is used to connect the OTDR to the
link-under-test. Launch bers are test leads that
enable the tester to overcome deadzone limitations to measure
the loss and refectance o the rst connector in the cabling. To test
the last connector on the ar
end o the link, attach a receive ber on the opposite end o the
link-under-test.
Additional fber best practice resources
To download other Fiber Best Practice white papers and or
additional resources,
visit www.fukenetworks.com/FiberBP
Contact Fluke Networks: Phone 800-283-5853 (US/Canada) or
425-446-4519 (other locations).
Email: [email protected].
Figure 1. Depiction o a typical OTDR trace.
Figure 2. Advanced troubleshooting capability,
such as highlighting questionable connectors
in the link-under-test.
