1-8
IM AQ7280-01EN
1.3 Optical Pulse Waveform Display
You can display the measured result as a waveform on the screen. You can zoom the displayed
waveform and move the position that is displayed.
How to View Optical Pulse Waveforms
The optical pulse applied to the optical fiber cable is reflected at different points of the optical fiber such
as its connections, bent sections, and the open end of the fiber. These sections generate loss. The
measured result is displayed as a waveform that has distance represented in the horizontal direction
and loss level represented in the vertical direction. On the waveform, detected losses or reflections are
known as events.
Incident ray
Backscatter
Splice
Connector
Bend
Open end
Near-end reflection
Splice loss
Approximated line
Reflection caused by a connector
Loss caused by bending
Reflection at the open end (Fresnel reflection)
Dynamic range (SNR = 1)
Optical fiber cable
Near-end Reflection
This is the reflection that occurs at the point where the AQ7280 and the optical fiber cable are
connected. This also includes the AQ7280’s internal reflection. In the section where this near-end
reflection is detected, even if there are other connections, the loss and reflections that occur at these
points cannot be detected. This section is the near-end dead zone.
When you are measuring a short distance, connect a launch fiber cable to reduce the effect of the
near-end reflection.
Backscatter
When light travels through an optical fiber cable, Rayleigh scattering caused by changes in the density
of materials that are smaller than the light’s wavelength and inconsistencies in the fiber's composition
generates loss in the optical fiber itself. The portion of the scattered light that travels in the direction
opposite to the direction of propagation is known as backscatter.
Small
material
Incident
ray
Backscatter
Optical fiber cable