10
Fig.3-1 Reflection Event
3.2.3
Non-Reflection Event
Non-reflection event brings loss on the whole transmission link of optical fiber, but
no light reflection. On the curve, non-reflection event is shown as drop of optical power,
as shown in Fig.3-2.
Fig.3-2 Non-reflection Event
3.2.4
Test Event
OTDR sends optical pulse into the optical fiber that waited for inspection, then,
begins to accept the returned optical signal immediately, and calculate the distance of
“
event
”
in the optical fiber. The further the event is, the longer the time for returning
back to otdr will be. The distance can be calculated according to the time when receiving
the event.
Through inspecting the curve of the reflected signal, the optical transmission
characteristics of optical fiber, connector and joint can be confirmed.
3.3
Measurement Functions of the OTDR
OTDR displays the power of the returned signal related to distance. The information
can be used to confirm the transmission quality of a fiber optic link.
3.3.1
Measurement Contents
of the OTDR
Position (distance) of event, result or fractured position of fiber optic link;
Attenuation coefficient of optical fiber in the optical fiber link;
Loss of a single event (for example, a optical connector or bending), or total losses
from end to end on the fiber optic link;
Reflection amplitude (or reflection level) of an event, such as connector.
3.3.2
Trace Analysis
of the OTDR
OTDR analyzes the curve automatically. Location of the curve:
Reflection event generated from connection and mechanical connector;
Non-reflection event (usually be fusion splice);
Optical fiber bundling: through scanning the first loss event that larger than the
