6. Common Failure Analysis and Troubleshooting
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.
After connecting the
network, the images of
several optical contact
points appear one or two
horizontal bright traces.
Power supply AC ripple
interference because of the bad
earth of equipment or power
supply.
Check grounding situation of the equipment, make
sure that every equipment in the line has been
reliably grounding and the grounding resistance
must be﹤4Ω.
After connecting the
network, the received
optical power of the
optical contact point is
unstable and changes
continuously. The
output RF signal is also
unstable. But the
detected optical output
power of the optical
transmitter is normal.
The optical fiber connector types
do not match, maybe the APC
type connect to PC type.
The optical fiber connector or
adapter may be polluted
seriously, or the adapter has been
damaged.
1. Check the type of optical fiber connector and
adopt the APC type optical fiber connector to
ensure the normal transmission of optical signal.
2. Clean the polluted optical fiber connector or
adapter. Specific operation methods see “Clean and
maintenance method of the optical fiber
connector”.
3. Replace the damaged adapter.
