Clean Cords are Reliable Cords

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Clean Cords are Reliable Cords-Seymour Goldstein
www.flukenetworks.com 2006-2017 Fluke
Corporation
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Clean Cords are Reliable Cords
Or, what a minor obsession with reliability looks
like. We dont get a lot of complaints about our
product quality, so when we do, it gets our
interest. After recently receiving a field
complaint that a users OTDR launch packs were
degrading rapidly, specifically the reflectance
on the LC/APC connectors, our team devised a
simple test to assess the problem. Two 160 meter
launch packs were randomly selected from
production stock. An actuator was setup that
would allow automated mating and un-mating of the
SC/APC connector pair. Connector attenuation and
reflectance using an OTDR were measured at the
beginning of the test and after every 25 mates.
Any outlier measured after a 25 mate cycle
warranted cleaning of the connector
endface. Cleaning was not done after every
mating because the actuator mechanics prevents
easy access, so the test was considered less than
ideal (i.e., what Fluke would recommend for
cleaning and inspecting). However, measurements
were done in a clean environment. Any measurement
change observed after a 25 mating cycle would
necessitate inspection, cleaning, then test
continuation. The goal of the testing was to
observe when and how connector attenuation and
reflectance would increase after 500 mates, 1000
mates, and beyond.
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Clean Cords are Reliable Cords
OTDR setup
A single-mode OTDR was used. The OTDR trace in
Figure 1 shows where the measurements were made
and how the trace appeared initially or after
cleaning.
Figure 2 shows how the OTDR trace appeared when
debris was found at the connector end face.
Notice the increase in the pulse height at the
cursor location found at the center of the trace.
Figure 1. OTDR trace with 0.27 dB connector
attenuation and -77 dB reflectance
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Clean Cords are Reliable Cords
OTDR setup
Figure 2 shows how the OTDR trace appeared when
debris was found at the connector end face.
Notice the increase in the pulse height at the
cursor location found at the center of the trace.
Figure 2. OTDR trace with 0.75 dB connector
attenuation and -43 dB reflectance
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Clean Cords are Reliable Cords
Connector attenuation data
Without apparent degradation in optical
performance (attenuation) between mated SC/APC
connectors, testing was concluded after 5,000
mates and de-mates. The connector end face was
cleaned a total of 7 times and only after
attenuation or reflectance degraded (which
accounts for the outliers). See a summary of the
attenuation data below and the raw data in Figure
3. After 500 insertions, the average attenuation
was 0.32 dB. After 500 to 1000 insertions, the
average attenuation was 0.39 dB. After 1000 to
2000 insertions, the average attenuation was 0.40
dB. After 2000 to 3000 insertions, the average
attenuation reached a peak of 0.45 dB. After
3000 to 4000 insertions, the average attenuation
dropped a small amount to 0.43 dB. Finally,
after 4000 to 5000 insertions, the average
attenuation dropped further to 0.40 dB.
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Clean Cords are Reliable Cords
Connector attenuation data
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Clean Cords are Reliable Cords
Connector reflectance data
The reflectance measured with an OTDR, except
for the outliers caused by debris, remained very
stable at -77 dB. See Figure 4 below.
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Clean Cords are Reliable Cords
Summary
We have demonstrated, with a sample of one, what
is possible from an SC/APC connector pair after
repeated matings/de-matings, if done in a clean
environment. For any outlier that appeared,
cleaning restored the next measurement to the
measurement prior to the outlier data point.
Testing stopped after 5000 matings which took
several days. Since the sample size was one,
by no means do these measurements represent all
connector performance. However, the measurements
on one sample do provide some insight into what
you might expect from your connectors if they are
cared for. So, protect your investment and keep
your connectors clean. Your launch cords will
thank you.
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