Bird Technologies Manual 7-9570-1-1
(Rough Draft)
08/19/16 Page 19
gle mode fibers only. All connectors between the
master unit and the remote unit should be of
angled type, otherwise problems with reflections
will arise which may cause severe problems in the
system.
The FOI has a nominal gain of 35 dB. The laser
transmitter should see a maximum composite
power in of approximately 0 dBm. This means that
for 0 dB attenuation in the DL direction a maximum
input of -35 dBm composite power is recom-
mended (when attenuators are set to 0 dBm). If the
DL attenuator is set to a higher value the maximum
recommended input is adjusted accordingly. The
output power of the laser is calibrated to 3000 µW.
This can be used to check the loss over fiber in the
remote because the remote reports the received
optical levels. The loss may be different in the UL
compared to the DL because of different wave-
lengths on the laser.
Safety and care for fibers
The laser is a Class 3b laser that
produces invisible infra-red coherent
light. Avoid looking into connected
fibers and receptacles. Not safe to
view with optical instruments. Always
put the protection caps on unused
fibers and receptacles.
Every time a fiber is disconnected and re-con-
nected care should be taken to avoid dust to settle
on the connector or in the receptacle. Clean with a
dry fiber cleaning tool before reconnecting the fiber
at all times. A single speck of dust can impact the
transmission severely. Do not touch the fiber ends
with your fingers. That will leave grease on the con-
nectors and may cause severe problems.
CENTRAL GATEWAY COMPUTER
The central gateway computer (CGW) is the overall
interface point for system management functions.
The CGW computer is connected to the master
unit and has routing, firewall functionality, alarm
logging, and access control for the complete DAS
system. Two types of CGW’s are used, either the
Remote Gateway Unit (RGW) or the Base Station
Gateway Unit (BGW). The RGW is a smaller com-
pact embedded solution while the BGW is a full
featured Linux server that can be set up in many
different ways. The gateway computer will assign
IP addresses to all the subunits in the master unit
and also for remote units when they are connected
to the system. This will create a protected sub-net
for the DAS system itself that should not be con-
nected directly to a LAN. Connections to a LAN
should only be made via the gateway computer.
2 DL
Paths
2 UL
Paths
Figure 12:
FOI
Module. Front plate close-up also shown.