ANSI/TIA 568-C standards require Method B (also known as 1 Jumper) for fiber testing, which uses a single jumper for setting a reference.

But when it comes to testing 12-fiber multifiber push-on (MPO) trunk cables commonly used for 10 and 40 gigabit permanent links in today’s data center, testing can become rather bewildering--especially with legacy testing equipment that does not have an MPO interface. Enter the 3 Jumper method.

The 3 Jumper Method

When testing MPO trunk cables using MPO to LC fanout cords that separate the 12-fiber trunk cable into single fiber channels, the 3 Jumper reference method is required to offset the additional loss.

The 3 Jumper method requires first connecting the main and remote test units to verify the SC-to-LC test reference cords performance (Step 1). The LC-to-LC test reference cords are then connected on both the main and remote units and tested using a singlemode LC adapter to ensure the best possible alignment (Step 2).

Once the SC-to-LC and LC-to-LC test reference cords are verified, a third test reference cord is inserted using an LC adapter on the main unit (Step 3).

Once all three test reference cords are confirmed, the third cord is removed and the test reference cords on the main and remote units can now be connected to the first pair of the MPO trunk cable (Step 4). This must be repeated five more times for each of the remaining pairs.


Instead of using a fanout kit, an LC-to-MPO cassette can be used. However, the cassette must be classified as low loss with no more than a 0.35 dB loss per cassette. Belden offers the industry’s lowest loss connectivity (0.2 dB for MPOs and 0.15 dB for LCs) that easily meet this requirement.

A Faster Option

If the 3 Jumper method using fanout cords seems like a time consuming, complex task for testing MPO trunk cables, your other option is to use one of the use one of the latest available testers with an MPO interface that measures power loss an validates polarity on 12 fibers in a single connector. This can make testing MPO trunks almost 90% faster. The MultiFiber™ Pro optical power meter from Fluke Networks is one example that offers an on-board MPO connector with built-in polarity verification.

Download our 10 Steps to Holistic Data Center Design white paper