FHO5000
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16.2 Terminology
Near-end reflection
A reflection occurs in the gap between OTDR and the connector for the optical fiber cable. Losses and reflections of the
connection points cannot be detected in the section in which this reflection is detected. This section is called a dead zone.
Backs cattering light
When light propagates through the optical fiber cable, a phenomenon called Rayleigh Scattering occurs due to the
nonuniformity of the density or constituents of materials smaller than the wavelength unit. The scattered light that is
transmitted opposite to the direction of propagation is called backscattering light.
Splice loss due to fusion
A splice loss occurs at the fused section mainly due to axis offset and angle offset.
Reflection due to connector connection
Unlike the fused section, a slight gap occurs in the connection section of connectors. Because the group refraction index
changes in this gap, a reflection occurs causing a loss.
Fresnel reflection at the far end of the optical fiber cable
Fresnel reflection occurs at the location where the optical fiber cable is broken or a location where the group refraction
index changes such as the far end of the cable (glass and air) when light enters the cable. If the end face of the optical fiber
cable is vertical, approximately 3.4 % (–14.7 dB) of the incident light power is reflected.
Dynamic range
Dynamic range refers to the difference between the backscattering light level at the near end and the noise (RMS = 1).
Dead zone
The locations where measurements cannot be made due to the effects of Fresnel reflection, connection point of
connectors, etc.
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