CT uses a Fluke MFTK light source and power meter set to quickly test our 12-core MPO singlemode fibres. This guide covers how to test the fibre but also how to calibrate the set if loss readings become inaccurate. Always replace dust caps on the test set and all cables. Always one-click clean your fibres before testing and before use.
To Test Cables
Open the drawer in the test rack and switch on the light source. This is the left-hand unit labelled with ‘1310nm Source’ written to the right of the screen. If you follow Fluke’s instructions exactly you should now wait for 5 minutes for the light source to stabilise however this is unnecessary for the style of testing we carry out. The light source will start up in automatic mode, which cycles through all 12 cores of the fibre one by one.
Switch on the power meter.
Remove the dust caps from the rugged 12 core connectors labelled Red MPO on the front panel. Clean the internal MPO connectors using the one-click cleaning pen. It is essential you regularly clean these connectors whilst using the test set to ensure accurate results. Even small amounts of dust and dirt can cause signal failures.
Take the 0.5m calibration cable from the drawer, remove the dust cap from one end and carefully clean the MPO connector. The one-click cleaning pens do not have a guide to fit these connectors but the pen can be aligned with the polished face of the MPO connector and will still clean it.
Plug this end onto the panel.
Repeat the process for the other end of the 0.5m calibration cable.
Wait for all 12 cores to be tested by the Fluke Power Meter. As this is the calibration cable, the Meter should read zero loss on all cores. See how to read the Power Meter display in the next section. If it does not read zero loss, try cleaning all the MPO faces of the cable and panel connectors again and replug the cable. If there is still high loss, you should recalibrate the system form the instructions below.
Reading the Power Meter
The Power Meter displays a lot of information but the important reading is any dots shown above the maximum loss level line. In this graphic, core 2 is reading a loss higher than permitted.
If a fibre passes, all 12 cores should remain below the maximum loss level line.
In some cases the Overall Pass/Fail indictor may show a failed fibre even if all cores are showing very low loss. This is due to one or more cores reading a negative loss value. If you use the up arrow to scroll through the core readings you will find a reading with a negative number. This core has failed because it’s impossible for the core to emit more light than the Source is putting into it. This will down to miscalibration of the unit. A negative reading of between -0.01 and -0.10 is acceptable for our testing however anything beyond this and the set should be recalibrated.
To Calibrate the Test Set
Follow the instructions above to the point of having the 0.5m calibration cable plugged in. More than ever, clean MPO ends are vital to the calibration process. If you are unsure about how clean the ends are, do it again!
On the Power Meter, press Menu until rEF is displayed. Wait until all 12 cores have a reading. A perfect calibration should have five dots being displayed on all 12 cores. If one core on shows one or two dots, clean your fibres again.
Once all 12 cores are displayed, press the F1 button to save the calibration.
Press the Menu button until LOSS is selected. Calibration is complete.
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