Cisco GS7000 Installation And Operation Manual page 165

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.
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.
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.
4
For standard receiver
Attenuate the light to simulate the
amount of light that should be at the
1.2 GHz 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 +2 dBm
at the detector will also generate
distortions.
Poor C/N Performance
For low input receiver
Attenuate the light to simulate the
amount of light that should be at the
1.2 GHz 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 -2 dBm at
the detector will also generate
distortions.
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