What is a Power Meter & Light Source?
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.
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 fiber 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?
Fiber Optic Cable to 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.