How to Measure the Loss in the APC Connector - PowerPoint PPT Presentation

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How to Measure the Loss in the APC Connector

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When we make an OTDR (Optical Time Domain Reflectometry) measurement, we use the launch cable to allow the trace to settle down after the pulse(s) are sent into the fiber, allowing us to see and analyse the start of the fiber being tested. This is because a large event will be seen in front of the connection on the trace usually caused by reflectance from the connector on the OTDR, thus not allowing us to make a good measurement of the first connection. The launch fiber also overcomes the issue of any dead zone (unseen event) that may occur if the pulse width is wider than the distance to a connector a short distance away from the OTDR connector. – PowerPoint PPT presentation

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Title: How to Measure the Loss in the APC Connector


1
How to Measure the Loss in the APC
Connector?-Barry Lindsley
www.flukenetworks.com 2006-2017 Fluke
Corporation
2
How to Measure the Loss in the APC Connector?
This question often gets asked in my classes at
the same time as when talking about launch
methods using launch and tail fibers. So lets
talk about launch fiber compensation.
3
How to Measure the Loss in the APC Connector?
Launch fiber compensation
When we make an OTDR (Optical Time Domain
Reflectometry) measurement, we use the launch
cable to allow the trace to settle down after the
pulse(s) are sent into the fiber, allowing us to
see and analyse the start of the fiber being
tested. This is because a large event will be
seen in front of the connection on the trace
usually caused by reflectance from the connector
on the OTDR, thus not allowing us to make a good
measurement of the first connection. The launch
fiber also overcomes the issue of any dead zone
(unseen event) that may occur if the pulse width
is wider than the distance to a connector a short
distance away from the OTDR connector. An
additional a short fiber cord may be added in
between the OTDR and the launch fiber, usually
called a sacrificial cord as it will sacrifice
its connector rather than connector on the launch
fiber. A launch fiber is typically used
in-conjunction with a tail fiber. This allows the
end of the measured fiber link to be measured. If
a tail fiber is not used we are not able measure
or analyse the end connector.
4
How to Measure the Loss in the APC Connector?
Launch methods
On Fluke Networks OptiFiber Pro there are four
different methods that can be made using launch
and tail fibers.
Launch only compensation
Where the length and loss of the launch fiber is
removed from the results. However, this will
result in the far end not being able to be
analysed. To overcome this, the fiber should also
be measured from the other end. If you use this
compensation method you will not be able to do
bi-directional averaging.
Launch and tail compensation
Where the length and loss of the launch and tail
fibers are removed from the measurement. This
method allows the far end connector as well as
the near end connector of the fiber link to be
evaluated. Another advantage of this method is it
allows a fiber link to be evaluated even if the
launch and tail fibers are different from the
link under test or there are a number of
different fibers within the link under test. This
method is required to be used if bi-directional
averaging is required.
5
How to Measure the Loss in the APC Connector?
Launch, fiber and tail compensation
Where the length and loss of the launch and tail
fibers are removed from the measurement. This
method has the advantage of allowing you to do
the compensation with a connected link included.
However, the disadvantage is you cannot access
your launch fibers.
Manual compensation
This method of compensation removes the length
and loss of the launch and tail fibers, but the
cord lengths of both the launch and tail fibers
are required to be entered manually on the
OptiFiber Pro. This guarantees that the OptiFiber
Pro knows where the first and last connectors are
located in the link even if they have no
measurable loss or reflectance.
6
How to Measure the Loss in the APC Connector?
This brings us back to the original question.
When we make an OTDR measurement on a link that
has an APC (Angled Physical Contact connector or
sometimes called Angle Polish Connector) at the
end of a link, its possible that the OTDR will
not see the end of the link because the APC has
no measurable reflectance or loss. To overcome
this, the manual compensation method should be
deployed on the OptiFiber Pro. If we simply use
the launch and tail compensation method, not
manual compensation as mentioned, we may not have
any measurable reflectance or loss at the end of
the link. In this situation, the OptiFiber Pro
produces the warning screen on the right.
7
How to Measure the Loss in the APC Connector?
If we use the suggested manual compensation
method, the OptiFiber Pro knows where the first
and last connectors are in the link because we
programmed in the length of the launch and tail
fibers. When an OTDR measurement is made and no
reflectance or loss is measured at the start or
the end of the link, a virtual event will be
marked on the trace. In addition this screen will
be produced. I hope this short article has
helped you understand how an OTDR can test a link
with an APC connector in the link and understand
the different methods of launch compensation.
8
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