What is the Purpose of a Power Meter & Light Source?

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A
Power Meter & Light Source is a low cost way to certify optical fiber.
These two pieces of test equipment are used to measure fiber optic light
continuity, loss and lastly the actual strength of the optical signal.

 

Signal
Loss

 

In
fiber optics when a beam of light which carries a signal goes through the
optical fiber the strength of that beam of light will diminish over distance.
This means the signal strength becomes weaker. This loss of light power will
affect the fiber optic network in a negative way. The loss of light power or
attenuation of the optical fiber is caused by two issues, scattering and
absorption of the light source. If the degradation is too great then
performance of the network will be affected.

 

The
following can be the cause of signal loss:

 

• Tight Bends
in the Cable

 

• Dirty or
Improperly Cleaned Connectors

 

• Too much
Stress on the Cable During Installation

 

• Poorly
Installed Connectors

 

• Improper
Splicing Technique

 

• Poor Cable
Quality

 

What
Equipment is Needed to Conduct a Power Meter & Light Source Test?

 

What
Training Does an Installer Need?

 

A
Power
Meter and Light Source are a pretty simple piece of test equipment to use.
The actual connection of the fiber to the test equipment is fairly
straightforward. If you are familiar with handling fiber optics the test is
very easy. If you are new to fiber optics this test should not present any
issues. A simple short video explaining the test should be all you need.

 

Why
use an OTDR in Place of a Power Meter & Light Source?

 

The
Power Meter and Light Source are more limited than an OTDR. A Power Meter can
only measure the received optical power. The OTDR can not only tell you there
is a break is in the fiber, it can also measure the distance between the test
point and the break. In addition, it is able to give you reflectance for each
connector. Even though the OTDR can reveal additional information, the Power
Meter and Light Source are still an important piece of optical fiber test
equipment and their importance should not be underestimated when testing an
optical fiber network.

 

How
Does A Power Meter & Light Source Work?

 

By
attaching a reference cable to the light source, power can be measured at the
opposite end of the fiber optic cable. The signal is sent from the light source
down the fiber. These two pieces of test equipment are used to measure fiber
optic light continuity, loss, and lastly the actual quality of the signal. In
short, it measures the power of the optical signal that has passed through the
fiber cable from the light source.

 

Steps
to Using a Power Meter and Light Source

 

Using
the Power Meter & Light Source to test a fiber optic cable is relatively
easy.

 

• First take
the reference cord end face and clean it with 99% reagent grade isopropyl
alcohol and lint free fiber optic wipes.

 

• Next plug
the reference cord into the light source and select the wavelength you are
testing. When testing a multimode cord attach a mandrel wrap to strip out the
higher modes of light that can interfere with the test results. A mandrel wrap
is not necessary for singlemode.

 

• Clean the
other end of the reference cord and insert that end into the Power Meter. Now
zero out the reference cord by hitting the “zero” button. After zeroing out, do
not unplug the reference cord from the Light Source. Take the cord to be tested
and clean one end, then attach the connector adapter. Clean the other end of
the patch cord.

 

• Remove the
reference cord from the power meter and attach to the test cord adapter, insert
the other end of the test cord into the power meter. The reading on the power
meter will give you the loss on the connector mated to the reference cord only.
To get the loss reading on the other end simply unplug the test cord from the
reference cord and switch the connectors. You have now completed the one cord
reference test.

 

• For a two
cord reference test attach a connector adapter to the reference cord and insert
the other end to the power meter. Zero out the power meter. You are now ready
to get a loss reading for the entire cord being tested.

 

• Take the
test cord and clean both ends with the cleaning alcohol and wipes. Connect the
test cord in between the two reference cords. The power meter will show a full
cord reading for total power loss. Record your loss as needed.

 

What
to Look for when Purchasing a Power Meter and Light Source

 

The
Power Meter and Light Source or Optical Loss Test Set are must have tools for
the fiber installer. While they are fairly simple tools to operate, care should
be taken in choosing the Power Meter and Light Source as there are many models
to choose from.

 

• Is the
equipment easy to use or does it require a huge manual?

 

• Operation of
this piece of equipment should almost be intuitive.

 

• Appearance
is important. Is it easy to hold?

 

• There should
be a minimal amount of buttons on the unit.

 

• Are screens
easy to read? Is it backlit?

 

• Is the Power
Meter and Light source calibrated?

 

• Does the
manufacturer calibrate?

 

• Can they
provide a calibration certificate traceable to NIST standards?

 

• Does the
unit come with a protective carry case?

 

• What about
battery life?

 

• Are adapter
caps included?

 

• Does the kit
include a dual wavelength multimode or single mode light source?

 

• Does it come
with interchangeable adapters allow flexibility with reference cords?

 

As
with any fiber optic test equipment, know the manufacturer. Find a reputable
company that will stand behind their equipment. If you have questions about
your choice, call or email the company and talk with a technical person that
can help you decide which piece of test equipment best suits your needs.
Remember, there are many manufacturers out there in the marketplace. Consider
only those with reputable firms that have a good track record. One that can
service and maintain your equipment if needed.