With the increasing use of fiber
optic cable in structured wiring, many electricians experienced in low-voltage copper work
are extending their skills to include fiber. Working with fiber requires training and the right
tools and testers to correctly install and maintain fiber optic cable.
“Just a few years ago, about 50 percent of
the owners of our test equipment told us they had
some amount of fiber on most of their projects,”
said Dan Payerle, business unit manager at Ideal
Networks, Sycamore, Ill. “Today, about 85 percent
of our customers have at least some fiber on most
of their projects. Even if the number of devices
connecting directly to the network with fiber is
not dramatically increasing, fiber is easier to integrate into security and automation systems.”
Greenfield CCTV surveillance is predominately Ethernet/IP, and control systems are
migrating to Ethernet/IP, effectively making
these systems extensions of the local area
network (LAN), Payerle said. As such, fiber
optic cabling can be used to extend the reach
of these systems with readily available, low-cost, optically enabled networking equipment
and media converters.
Testing is a critical component of installing
and maintaining any structured-wiring system,
and there are tests specific to fiber cable.
“The most basic test is performed with a
visual fault locator,” Payerle said. “This device
utilizes a visible red laser light in the 635–650-nm
[nanometer] spectrum to check cable continuity
and identify connectors to check polarity.
“Next, an optical power meter is the most
essential measurement device. Like a wire
map tester for copper cabling, [it] is used to
troubleshoot the majority of fiber cabling and
equipment issues. When connected directly to
the output port of an optical device, the power
can be measured and compared to the device’s
specifications to identify faulty transmitters.
The power meter can be used to test the insertion loss of the cabling by comparing the optical
power at the far end of cabling to the output
power directly at the transmit port of equipment.
“A power meter/light source or optical loss
test set [OLTS] is used to perform Tier 1 certification of optical cabling. We find that one of the
issues that most confuses the users of testers is
the process of setting the calibration/reference.
The standards recognize three methods of setting
the reference value of an OLTS: one-jumper, two-jumper and three-jumper methods,” Payerle said.
The fundamental tools and measurements
used to test fiber have not changed much in the
past year, but advances in analysis software and
test tool user interfaces have improved testing
efficiency. One example is the use of linear “
pictograms” to represent the segments, connectors and
splices on an optical time-domain reflectometer
(OTDR) instead of the traditional “trace,” which
requires interpretation by an experienced operator.
“Additionally, both the TIA [Telecom-
munications Industry Association] and ISO
[International Organization for Standardization]
are modifying their field-testing standards to
introduce reference-grade test cords,” Pay-
erle said. “These cords use high-precision
connectors that have less mated loss than
with standard cords. Technicians will need to
know which type of cords are being used with
their test equipment to ensure they calculate
the proper loss budgets when testing optical
cabling. Using standard-grade cords with loss
budgets calculated with reference grade values
can result in failing links that are actually good.
Conversely, using reference-grade cords with
loss budgets calculated with standard-grade
values will result in measured loss values that
are lower than the network will experience.”
Harley Lang, director of product marketing at
Fluke Networks, Everett, Wash., said the fiber
cabling market has grown most significantly in
recent years from enterprise campus and data-
“Of course, we see fiber installations for enterprise backbone cabling and longer distance
runs for security, but this has been the case for
many years,” Lang said, giving some examples
of basic fiber tests.
“Connectivity,” he said. “[This] tests to confirm that light signals can travel from one end of
the fiber to the other. Typically performed with
a visual fault locator [VFL], this can be helpful
for troubleshooting and managing polarity, but
it is not sufficient to ensure fiber performance.
“Inspection: Since most fiber problems can
be traced to connector contamination, inspecting the end-face before connecting can prevent
most fiber problems. Inspection cameras range
from simple optical microscopes to more sophisticated testers that can automatically provide a
pass or fail indication as well as document the
condition of the fiber end-face.
“Loss testing: This test indicates whether
the quality and design of the fiber link is sufficient to allow the signal to reach the far end
with sufficient strength to ensure free communications. Simple power meter and light source
testers can manually measure the loss of a fiber link, while more sophisticated [OLTS] can
automate the process, providing more efficient
certification of cabling, two fibers at a time, at
multiple wavelengths, and in both directions.
Ideal Networks’ OTDR II and OC1 are in
one touch-screen housing with different
Fluke Networks’ FI-7000 fiber inspector
provides a 1-second pass/fail certification
of fiber connector end-faces.
BY JEFF GRIFFIN
NEW LOW-VOLTAGE HORIZONS