If an OTDR trace shows one optical splice but there are actually two known splices, what is likely the cause?

When analyzing an OTDR (Optical Time-Domain Reflectometer) trace, the appearance of only one optical splice when two are known to be present can often be attributed to the settings used during the testing process. If the pulse width is set too long, it can lead to an inability to resolve closely spaced events in the fiber, such as multiple splices.

Setting the pulse width longer than necessary can cause the OTDR to average the reflected signals over a greater distance, essentially merging the two splices into a single event on the trace. This phenomenon occurs because the longer pulse width increases the measurement's resolution threshold, making it difficult for the OTDR to distinguish between two closely spaced optical events.

Understanding how OTDR settings impact measurement data helps technicians properly configure their tools to obtain accurate readings. In this context, ensuring an appropriately short pulse width is crucial for identifying multiple events in the fiber and obtaining a precise optical trace.