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8. Common Failure Analysis and Troubleshooting
Failure phenomenon
Failure cause
Solution
After connecting the
network, the image of
the optical contact point
has obvious netlike
curve or large particles
highlights but the image
background is clean.
1. The optical input power of the
optical receiver is too high, make
the output level of the optical
receiver module too high and RF
signal index deteriorate.
2. The RF signal (input the optical
transmitter) index is poor.
1. Check the optical input power and make
appropriate adjustments to make it in the
specified range; or adjust the attenuation of
optical receiver to reduce the output level
and improve index.
2. Check the front end machine room optical
transmitter RF signal index and make
appropriate adjustments.
After connecting the
network, the image of
the optical contact point
has obvious noises.
1. The optical input power of the
optical receiver is not high
enough, results in the decrease of
C/N.
2. The optical fiber connector or
adapter of the optical receiver has
been polluted.
3. The RF input signal level of the
optical transmitter is too low,
make the modulation degree of the
laser is not enough.
4. The C/N index of system link
signal is too low.
1. Check the received optical power of the
optical contact point and make appropriate
adjustments to make it in the specified range.
2. Improve the optical received power of the
optical contact point by cleaning the optical
fiber connector or adapter etc methods.
Specific operation methods see “Clean and
maintenance method of the optical fiber
connector”.
3. Check the RF input signal level of the
optical transmitter and adjust to the required
input range. (When the input channels
number less than 15, should be higher than
the nominal value.)
4. Use a spectrum analyzer to check the
system link C/N and make appropriate
adjustments. Make sure the system link
signal C/N
﹥
51dB.
After connecting the
network, the images of
several optical contact
points randomly appear
obvious noises or bright
traces.
The optical contact point has open
circuit signal interference or
strong
interference
signal
intrusion.
1. Check if there is a strong interference
signal source; change the optical contact
point location if possible to avoid the
influence of the strong interference signal
source.
2. Check the cable lines of the optical contact
point, if there is shielding net or situation
that the RF connector shielding effect is not
good.
3. Tightly closed the equipment enclosure to
ensure the shielding effect; if possible add
shielding cover to the optical contact point
and reliable grounding.
