EXFO FTB-7000 OTDR for FTB-200 v2 - Manual (Page 315)

Description of Event Types
OTDR 301
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.
³
This event is often caused by splices, macrobends, or microbends in
the fiber.
³
A loss value is specified for non-reflective events. There is no
reflectance specified for this type of event.
³
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 53).
Reflected power
(dB)
Distance
(km)
Non-reflective
event
Linear downward slope
due to Rayleigh
backscatter