Yamasaki Y30 Series User Manual page 12

Distance calculation formula of the OTDR: Distance = (c/n) × (t/2) Among
which: c= speed of light in vacuum (2.998 x 108 m/s)
t = Time delay between transmitted pulse and received pulse
n = refractivity of optical fiber during testing process (nominated by manufacturer)
When displaying the whole trace, each point on the trace graph represents the average value of
several sampling points. The value of each sampling point can be found by reducing or magnifying the
trace.
Fig. 5-1. THE OTDR Principle Diagram
5.3 Instruction of Events Categories
Events on optical fibers indicate abnormal points that have brought loss or a sudden change of
reflection power beyond the normal scattering of optical fiber material, including various kinds of
connections and bending, loss of flow or fracture on the optical fiber link.
Event points displayed on the screen are the abnormal points in the optical fiber that led to a deviation
of the trace, which are classified with special symbols on the trace. Events include "reflection event" and
"non-reflection event".
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