Issue link: https://www.e-digitaleditions.com/i/1066130
48 I ICT TODAY in the system. It will pass or fail based on the polarity of the system that it tests. TIER ONE TESTING The main challenge of Tier 1 testing an MPO system is setting the reference in different scenarios, because it depends on whether the system is pinned or unpinned. If using a test set that has pinned ports, use an unpinned to unpinned test cord to do a one cord reference. One cord reference, which is one cord between the transmitters and the receiver, is the recommended reference for testing links. If the test set is pinned, use an unpinned to unpinned test cord to reference it. The technician cannot verify the reference without adding a third cord. When adding in the receive cord, which would be unpinned to unpinned, a pinned system can be tested. The standards recommend that the records are verified after a reference is set. This is done by connecting the launch cord and receive cord through a high-quality coupler or adapter. Then, do an auto test and confirm that the loss is below a specific value; the loss value depends on whether singlemode or multimode fiber is being used. This cannot be done with MPO, because if there are two unpinned to unpinned cords, they cannot be connected together. What is needed is a third cord that is pinned to pinned and two adapters. This results in a higher loss. To address this issue, there are some MPO connectors available on the market today that allow pins to be either retracted, or removed, and then reinstalled. These connectors can help with test cord issues and solve some of the pinned to unpinned challenges. The easiest way to test MPO with an end-to-end link or channel is by using a dedicated MPO tester with MPO ports. This has an MPO source at one end and an MPO power meter at the other end. Start by setting the reference and ensure the use of the correct pinned or FIGURE 11: Tier 1 testing for MPO is loss length testing. The MPO tester can also be set up to conduct a pass/fail analysis of polarity. unpinned cables. Once the reference is complete, press the auto test button and all 12 fibers are tested for loss in a matter of six to seven seconds. This test will check polarity, measure length, and provide a pass or fail result based on loss criteria. Figure 11 provides an example of a singlemode optical fiber test at 1310 and 1550 nm. Their loss has been compared to a limit. In this case it passed. Things start to get more complicated when testing QSFP to LC configurations. The easiest way to do it is to use the same tester with a light source at one end— in this case on the left side—and a power meter on the other end. Do the one cord reference of MPO. The receive cord is an MPO to LC fanout cable instead of an MPO to MPO cord. In this case, the system has 12 individual LC connections or six duplex LC connections plugged into a cassette. Then, conduct an MPO auto test for loss, length and polarity of all 12 fibers. The other way to test