What is likely to cause an OTDR trace to show one optical splice when two are known to exist?

What is likely to cause an OTDR trace to show one optical splice when two are known to exist?

• A. The index of refraction is incorrect
• B. The pulse width is set too long
• C. Distance calibration fault
• D. Measurement mode is incorrect

Answer: (B)

A long pulse width can indeed lead to the appearance of one optical splice on an OTDR trace when two exist. This is because a longer pulse width means that the OTDR emits longer bursts of light, which results in a broader measurement window. When the broadening occurs, the individual events, such as two splices located closely together, may become indistinguishable from one another and appear as a single event due to the overlap of their reflections. In a scenario with closely spaced splices, using a shorter pulse width would provide a more granulated view of the events, allowing the OTDR to differentiate between them. Therefore, setting the pulse width too long can mask multiple events, leading to the misinterpretation of the trace. The other options relate to factors that could cause inaccuracies in measurement but would not specifically lead to two splices appearing as one in the trace. For example, an incorrect index of refraction would impact the accuracy of distance measurement rather than the visibility of the splice events themselves. A distance calibration fault might lead to misread distances or measurements but wouldn't necessarily cause overlapping events to appear as one. An incorrect measurement mode might change how the signal is analyzed but wouldn’t fundamentally alter how closely spaced events are resolved in the trace

A long pulse width can indeed lead to the appearance of one optical splice on an OTDR trace when two exist. This is because a longer pulse width means that the OTDR emits longer bursts of light, which results in a broader measurement window. When the broadening occurs, the individual events, such as two splices located closely together, may become indistinguishable from one another and appear as a single event due to the overlap of their reflections.

In a scenario with closely spaced splices, using a shorter pulse width would provide a more granulated view of the events, allowing the OTDR to differentiate between them. Therefore, setting the pulse width too long can mask multiple events, leading to the misinterpretation of the trace.

The other options relate to factors that could cause inaccuracies in measurement but would not specifically lead to two splices appearing as one in the trace. For example, an incorrect index of refraction would impact the accuracy of distance measurement rather than the visibility of the splice events themselves. A distance calibration fault might lead to misread distances or measurements but wouldn't necessarily cause overlapping events to appear as one. An incorrect measurement mode might change how the signal is analyzed but wouldn’t fundamentally alter how closely spaced events are resolved in the trace