User Manual

87
MN024-08
Each remote unit is provided with an AGC system which comes in after the optical-to-RF
conversion. This AGC can correctly compensate optical losses when these are estimated to be
<3 dB. In case optical losses are in the 3dB- 4dB range, the AGC is said to be “out of range”:
the whole system still work, but AGC is near to its borderline levels. The DL power LED switches
on when the estimated optical losses are >4dB, the AGC not being able to compensate these
losses any more.
As shown in the previous table, the same red LED switches on to reveal any major failure.
Following the troubleshooting procedure reported hereinafter it is possible to better understand
what problem occurred
.
Quick troubleshooting procedure
(The following procedure is summarized by the flow-chart in fig. 3.40a)
In case the red LED is ON, please follow these steps:
1. First of all, clean the optical adapters
2. If the problem still persists, refer to the fibre optic DL troubleshooting to
check if optical cables or optical connections have any problem on DL path.
3. If previous actions didn’t make the LED switch off replace the unit with a
new one or contact for assistance.
Fibre optic DL troubleshooting
(The following procedure is summarized by the flow-chart in fig. 3.40b)
1. Check if there is any point where fibre experiences a short radius of
curvature. In this case, rearrange the optical path in order to avoid sharp
bends (if necessary, replace the optical cable with a longer one). If TFLN red
LED switches off, troubleshooting has been successfully carried out.
Otherwise, follow next steps.
2. Check if SC-APC connectors are properly installed at both fibre ends. In
case they are not, fix better SC-SPC connectors to adapters. If TFLN red
LED switches off, troubleshooting has been successful. Otherwise, follow
next steps.
3. Disconnect the optical fibre and clean it better at both ends then clean the
SC-APC ports on both the TFLN and the remote unit. Re-connect the fibre to
relevant ports after cleaning. If it doesn’t made TFLN red LED switch off,
follow next steps.
4. Disconnect the optical SC-APC connector from remote unit DL port, and
measure the output power P
OUT
(DL) at the corresponding fibre end. Then,
go to the TFLN side, disconnect the optical SC-APC connector from TFLN DL
port and measure the input power P
IN
(DL) coming out of the TFLN DL port.
Calculate the DL fibre attenuation A
DL
as A
DL
[dB] = P
IN
(DL) – P
OUT
(DL)
a. If A
DL
> 4dB, then the fibre optic cable has some problems. Replace it
with a new one.
b. If A
DL
< 4dB troubleshooting procedure has not identified the problem.
Refer to supervision system or contact assistance.
TFAx
CaseF