EXFO OTDR 2 - Manual (Page 198)

Description of Event Types
190 OTDR
Reflective Event
Reflective Event
Reflective events appear as spikes in the fiber trace. They are caused by an
abrupt discontinuity in the index of refraction.

Reflective events cause a significant portion of the energy initially
launched into the fiber to be reflected back toward the source.

Reflective events may indicate the presence of connectors,
mechanical splices, or even poor-quality fusion splices or cracks.

Normally, loss and reflectance values are specified for reflective
events.

When the reflective spike reaches the maximum level, its top may be
clipped due to the saturation of the detector. As a result, the dead zone
(minimum distance for making a detection or attenuation
measurement between this event and a second nearby) may be
increased.

If you set thresholds, the application indicates a reflective fault in the
events table, whenever a value exceeds reflectance or connector loss
thresholds (see Setting Pass/Fail Thresholds on page 39).
Reflected
power (dB)
Distance
(km)
Reflective events
Clipped level