Cisco Model GS7000 4-Port Node 1 GHz with 42 54 Split Installation Guide
Poor C/N Performance
OL-29643-02
159
Notes
These notes apply to the previous troubleshooting flowchart.
Note Description
1
RF drive level to the laser must be set to the laser manufacturer’s
specification.
specification.
2
It is possible that the distribution module is set up incorrectly. See the
pad and equalizer selection charts in Appendix A for correct pad and
equalization. The C/N performance will suffer if the RF levels are too
low into the first gain stage or the interstage.
pad and equalizer selection charts in Appendix A for correct pad and
equalization. The C/N performance will suffer if the RF levels are too
low into the first gain stage or the interstage.
3
It is important to monitor the DC level at the receiver module because in
the process of cleaning the connectors, the transfer of light through each
connector may improve or degrade. The DC reading should degrade if
there is a reflection in the path depending on the severity of the core
mismatch. Scratches on the surface of the fiber of the connector can cause
reflections. Scratched connectors must be replaced.
the process of cleaning the connectors, the transfer of light through each
connector may improve or degrade. The DC reading should degrade if
there is a reflection in the path depending on the severity of the core
mismatch. Scratches on the surface of the fiber of the connector can cause
reflections. Scratched connectors must be replaced.
4
For standard receiver
For low input receiver
Attenuate the light to simulate the
amount of light that should be at
the GS7000 Node and rerun the
C/N performance. Add
components into the path one at a
time until the problem is found.
Change jumpers, couplers, fibers
and connectors one at a time,
taking C/N measurements after
each change.
A phenomenon called “shot noise”
will occur if the light level is too
high into the receiver. This is noise
generated by the photo diode
when the light is converted back to
RF. An optical input level
exceeding +3 dBm at the detector
will also generate distortions.
amount of light that should be at
the GS7000 Node and rerun the
C/N performance. Add
components into the path one at a
time until the problem is found.
Change jumpers, couplers, fibers
and connectors one at a time,
taking C/N measurements after
each change.
A phenomenon called “shot noise”
will occur if the light level is too
high into the receiver. This is noise
generated by the photo diode
when the light is converted back to
RF. An optical input level
exceeding +3 dBm at the detector
will also generate distortions.
Attenuate the light to simulate the
amount of light that should be at
the GS7000 Node and rerun the
C/N performance. Add
components into the path one at a
time until the problem is found.
Change jumpers, couplers, fibers
and connectors one at a time,
taking C/N measurements after
each change.
A phenomenon called “shot noise”
will occur if the light level is too
high into the receiver. This is noise
generated by the photo diode
when the light is converted back to
RF. An optical input level
exceeding -1 dBm at the detector
will also generate distortions.
amount of light that should be at
the GS7000 Node and rerun the
C/N performance. Add
components into the path one at a
time until the problem is found.
Change jumpers, couplers, fibers
and connectors one at a time,
taking C/N measurements after
each change.
A phenomenon called “shot noise”
will occur if the light level is too
high into the receiver. This is noise
generated by the photo diode
when the light is converted back to
RF. An optical input level
exceeding -1 dBm at the detector
will also generate distortions.