OPTICAL MASTER UNIT MARK I
PRODUCT DESCRIPTION AND USER’S MANUAL
Cobham Wireless – Coverage Date: 4-Jan-18 www.cobham.com/wireless
Document number:A1829300UM Rev. 3.1
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1.3.2 Cascading OMUs
Up to four OMUs can be cascaded and operate up to 24 repeaters as one system: one Master OMU
and three Slave OMUs.
This type of topology requires only one Control module and one modem (at the Master OMU). All
OMUs and hosted Repeaters are managed as a single system via the Master OMU.
Figure
1-3. Four OMUs cascaded in one system
1.3.3 Expansion using Multi-color Laser System
The number of Repeaters supported by each OMU can be expanded using multi-coloured laser
systems.
A laser system with two colours can operate one repeater for each fibre optic converter in an OMU-
Repeater system – one color is used for the uplink and one for the downlink. A laser system with
three or more colours can operate two or more repeaters per fibre optic converter. One color is used
for the downlink which is the same for all repeaters, and in the uplink each repeater has its own
color.
The connection from one repeater to the next is done via so called add-drop couplers.
The difference in distance between the repeaters and the OMU can be compensated for
automatically.
Two repeaters are connected to the same converter in the OMU via the same fibre but the
wavelength for the uplink differs between the units. Slave 1: 1550 ± 3 nm, Slave 2: 1510 ± 3 nm.
The downlink signal is the same for both repeaters.
Figure 1-4. Dual-colour Fibre Connections to Two Repeaters
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