Issue link: https://www.e-digitaleditions.com/i/1066130
46 I ICT TODAY • SFP to SFP connectivity: Over multimode fiber (without SWDM technology), this will support up to 10 Gb/s. In a classic architecture, there is an MPO trunk cable between two cassettes; the cassettes break down to LCs, and the LCs connect to a switch at one end and a server at the other, or a switch at both ends. In this case, always inspect the MPO connection to the cassettes, both inside the cassette and the trunk cable itself. The loss, length and polarity test can be done at the duplex LC drops with a normal, duplex optical loss test set (OLTS). With pre-assembled cables that go in and out of the trunk, it is not usually necessary to conduct a loss, length and polarity test of that trunk unless it has been damaged during installation. If that is the case, it will be discovered when testing the LC drops. The technician may need to conduct a troubleshooting event to find the fault. MPO connections; then use an MPO tester to test those links or channels. Finally, do a quick auto test of all 12 fibers for loss, length and polarity at the same time. As emphasized earlier, inspecting the fiber end faces is critical. MPO is particularly prone to collecting debris that can cross-contaminate, possibly cause damage, and certainly affect the performance of the system, which has a much lower loss requirement than previous systems. So inspect the fiber end face before connecting. Check to see if they are clean or run an automated pass/fail analysis with the test equipment. If it is dirty, clean it. Inspect again; ask if it is clean. Connect only when it is absolutely clean. FIGURE 9: This diagram shows what to inspect and test for three configurations: SFP to SFP, QSFP to SFP and QSFP to QSFP. • QSFP at one end and SFPs at the other: Consider the following example in which there is 4 by 10 Gb/s with 40GBASE-SR4 optics at one end and four individual servers, each running at 10 Gig at the other end. An MPO runs through an adapter plate at the left side, through an MPO trunk cable to an MPO cassette. That MPO cassette breaks down to three 8-fiber MPOs. This is an interesting test case with an MPO on one end and an LC connector on the other end. Again, it is important that the technician inspects all of the MPO connections before anything else is connected. A test from MPO to simplex can be conducted. Put an MPO light source on the left-hand side and take a simplex power meter to work through the 8 or 12 fibers on the right-hand side. The other technique is to use a fanout cable and test MPO to MPO. • QSFP to QSFP: This system configuration is the easiest to test. If doing 40/100 Gig, for example, 100GBASE-SR4, test native MPO from end to end. Inspect all the