Viavi OneExpert DSL ONX-580, User Manual

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Chapter 15 Test Results
OneExpert DSL User's Guide
22052280, Rev. 015 April 2019 272
TDR
A TDR (Time Domain Reflectometer) is used to identify and locate buried splices, shorts and
low resistance faults, opens, bridge taps, load coils, and wet cables.
Velocity of Propagation (VoP) is the speed of the TDR signal traveling down the wire pair
relative to the speed of light. The OneExpert DSL uses this value to convert reflections to
distance. It is important to select the correct cable gauge and fill for an accurate distance
calculation.The default value is appropriate for 24–26 AWG (4–5 mm) telco aerial cable and
provides sufficient accuracy in most situations.
The following table describes the TDR result.
RFL
You use an RFL to find resistive faults such as poor splices, water, shorts, and battery
crosses by cable damage (caused by rodents, the weather, etc.).
Spectral
Radio frequency interference from digital services or AM radios can reduce the performance
of a copper wire. The spectral test can detect and measure the existence of such
interference.
Comparing traces is useful to troubleshoot anomalies such as excessive impulse noise
on the copper loop, large noise spikes on a spectral graph, and DSL errors impacting
performance.
Noise
You measure noise to determine the amount of noise in a frequency range used for digital
services such as ADSL and VDSL (wideband) or in voice frequencies (narrowband).
Impulse Noise
Impulse noise is used to check for the presence of noise spikes that disrupt digital services.
RX and TX Tones
You use tones to check cable performance (attenuation) at higher frequencies used for
digital services (wideband) or in voice frequencies (narrowband).
Range Accuracy
0 to 30,000 ft (10 km) ± 0.5% of distance