Issue link: https://www.e-digitaleditions.com/i/1386104
July/August/September 2021 I 23 Bend as seen on an OTDR trace Bend as seen on an Event Map While multimode transceivers are extremely tolerant of reflection, singlemode transceivers are not. When looking at an OTDR trace that graphically displays the characterization of a fiber link, experienced OTDR users can typically recognize reflective events for launch cords, connectors, mechanical splices, fusion splices, missmatched fibers, and the end of the link. However, not everyone is a trace analysis expert or perhaps a technician is simply out of practice, which may deter some from adopting an enhanced OTDR testing strategy. Fortunately, some OTDRs today come with advanced logic that automatically interprets the trace and provides a detailed graphical map of events that indicates the location of connectors, splices, and anomalies. These event maps are ideal for those who may not be proficient at reading a trace, and it can also be a valuable training FIGURE 2: Bends are characterized by a lack of reflectance with higher loss at longer wavelengths as shown in the trace at left. Advanced OTDRs recognize events like these and present them in an easy-to-interpret manner (right), allowing technicians to switch back and forth between the two displays. In addition, final Tier 1 insertion loss test results are typically required for definitive proof of compliance, so if testing fails and there is the need to characterize and troubleshoot with an OTDR, Tier 1 testing will still have to be performed again. OTDR TRACES DO NOT HAVE TO BE INTIMIDATING The OTDRs display results in a trace by plotting reflected and backscattered light versus distance along the fiber, essentially characterizing any reflective and non-reflective events in a fiber link. The OTDR traces have several common characteristics, such as the initial input pulse that occurs at the connection to the OTDR and a large spike followed by a dramatic drop that indicates the end of the fiber. skills. As shown in Figure 2, if technicians are not quite sure what type of event they are looking at on the trace, they can switch back and forth between the trace and the event map to help test their skills and verify what they are seeing. tool to help technicians improve their interpretation