Textron GREENLINE 920XC Series, Training

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OTDR Basic Operation
The Optical Time Domain Reflectometer (OTDR) is an instrument that uses the inherent backscattering
properties of an optical fiber to detect faults and categorize its condition. The OTDR sends high-power
pulses of laser light down the fiber and captures the light that is reflected back (much like a radar system).
By measuring the timing and power levels of the return pulses, the instrument correlates the reflected
information with physical locations along the fiber and displays a “trace” that shows optical power versus
distance. Attenuation of the fiber is displayed as the slope of the trace. Interruptions such as splices,
connectors, bends, breaks or flaws in the fiber appear as transitions (“events”) that represent their nature
and location.
Display Processor
Detector
Laser
Coupler
Fiber
under test
Probe
pulse
End of
fiber
Rayleigh
backscatter
Fresnel
reflection