March/April 2019 I 55
perform the tests and provide a complete report with
pass/fail verdict and a link view to the different network
elements, their location and which are problematic.
When troubleshooting a live network, use an OTDR
equipped with a singlemode live port using an out-ofband
1625 nm wavelength. This allows networks with
live traffic to be tested without interfering with other
active users. With the multi-pulse OTDR technology,
one can detect fault locations accurately.
OTDRs are also helpful at finding macrobends, which
are the second biggest cause of network problems.
Macrobends can be caused by improper fiber handling.
The light in the optical fiber “leaks out” of the fiber
when it is bent. When there is a macrobend, it presents
itself as a higher loss at the higher wavelength. By using
an OTDR at two different wavelengths, the technician
can validate whether the loss occurs at the higher
wavelength. An iOLM will also pinpoint the location
of a macrobend.
SERVICE ACTIVATION
To test service activation, use a PON power meter,
which is a pass-through unit that checks the power both
upstream and downstream. One end of the meter is
connected to the OLT and the other end to an ONT.
The pass-through connection allows the ONT and OLT
to communicate with each other to confirm all signals
are present. The unit is equipped with filter detectors
for individual measurements of wavelengths. It supports
GPON and next-generation PON and with special
built-in PON awareness capability it adjusts itself
automatically to the active wavelength to perform
a power reading.
REPORTING
The last element for POL is reporting. The different tools
discussed all provide PDF reports of the results. For
example, iOLM provides a complete report with a view
of all the different elements on the network. The
technician sees a global pass/fail status as well as the
individual status of every element identified.
Furthermore, the technician would know the loss
and reflectance for each of those events, so if there is
a problem it is known right away where it is located.
Tools, like OLTS, provide reports of the bidirectional
testing with the loss and optical return loss and length
link. When inspecting connectors with a fiber inspection
probe, a complete report is generated with pictures of
the connector end phase with overlay of the analysis
that was performed on them, as well as global status and
a table with events of the different zones that details the
quantity and size of any defects.
CONCLUSION
For network managers and building owners who are
installing a new network, either in a greenfield situation
or a complete forklift upgrade, deploying POL
technologies and singlemode optical fiber lays the
foundation for a future-proofed network that will last
for decades to come. Built on standardized, mature
and mass-market PON technologies, an increase of LAN
speeds can be achieved without any impact on the
cabling infrastructure and with only minor updates
of the end-point electronics. The evolution is not
disruptive and can be incremental, as different PON
technology generations can coexist on the same network.
AUTHOR BIOGRAPHIES: Guillaume Lavallee is the product
line manager at EXFO, a company specializing in Telecom Test &
Measurement and Service Assurance. He is responsible for the
optical products in the installation and maintenance division.
Email: guillaume.lavallee@exfo.com.
Steven Van Den Bergh is responsible for business development
for POL solutions in Western Europe for Nokia. Steven can be
reached at steven.van_den_bergh@nokia.com.
Cemil Canturk is the senior marketing manager, Optical LAN,
for Nokia in Belgium. Previously, he worked in Fixed Network
Presales and Business Development for Nokia’s Europe, Middle
East and Africa regions. Email: cemil.canturk@nokia.com.
This article was written on behalf of the TIA’s Fiber Optic
Technology Consortium, which represents technology leaders
committed to providing the most current, reliable and vendor
neutral information about fiber optics and related technologies for
advancing new and better communications solutions and the
Association for Passive Optical LAN, a non-profit organization
composed of manufacturers, distributors, integrators, and
consulting companies who are actively involved supporting the
growth and education of the Passive Optical LAN industry.
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