What happens to the OTDR's ability to distinguish between events when pulse width is widened?

When the pulse width of an Optical Time Domain Reflectometer (OTDR) is widened, the device's ability to distinguish between closely spaced events decreases. This reduction in resolution occurs because longer pulse widths mean that the OTDR is sending out a broader light pulse. As a result, any reflections or events that occur within the time duration of that expanded pulse may overlap and be interpreted as a single event rather than multiple distinct events.

To visualize this, consider that a narrow pulse results in a more precise measurement of time and allows the OTDR to detect smaller changes or events in the fiber's characteristics, such as splices or faults. Conversely, with a wider pulse, the time resolution decreases, leading to the merging of reflections in space, making it more challenging to accurately pinpoint and analyze individual events along the fiber optic link.

Thus, the correct understanding is that widening the pulse width ultimately reduces the capability of the OTDR to distinguish between those closely spaced events. This concept is fundamental when optimizing OTDR settings for effective fiber optic network testing and troubleshooting.