What can be located at the start of the knee on an OTDR trace?

The start of the knee on an OTDR (Optical Time-Domain Reflectometer) trace indicates a transition in the optical signal. This area is crucial because it can show both reflective and nonreflective events.

Reflective events are where there is a discontinuity in the refractive index, such as connectors, splices, or breaks in the fiber, causing a portion of the light to reflect back toward the source. Nonreflective events include things like bends or fiber loss, which do not cause a return signal but still affect the power of the signal traveling down the fiber optic line.

When examining the trace, both types of events can be identified at the knee. It reflects the initial point of significant changes in the signal, where the interaction of the fiber's characteristics causes variations that can be read by the OTDR. Thus, the knee provides insight into both types of events, making it essential for diagnosing and understanding the state of the fiber optic network.