EXFO OTDR 2 - Manual (Page 197)

Description of Event Types
OTDR 189
Non-Reflective Event
Non-Reflective Event
This event is characterized by a sudden decrease in the Rayleigh
backscatter signal level. It appears as a discontinuity in the downward
slope of the trace signal.

This event is often caused by splices, macrobends, or microbends in
the fiber.

A loss value is specified for non-reflective events. There is no
reflectance specified for this type of event.

If you set thresholds, the application indicates a non-reflective fault in
the events table, whenever a value exceeds the loss threshold (see
Setting Pass/Fail Thresholds on page 39).
Reflected power
(dB)
Distance
(km)
Non-reflective
event
Linear downward slope
due to Rayleigh
backscatter