Westermo MD-63 B - Manual (Page 6)

12 6071-2022
Power budget
The MD-63B is designed to be used with Manchester coded protocols. This means that the
power budget varies depending on the number of preamble bits in the protocol. Preamble
bits are transmitted before the actual data and are used in order to synchronise the receivers
in the network. (see figure below)
The MD-63B uses these preamble bits as well to stabilise its receiver. This does mean that
a 10% distortion is applied to the preamble bits through the MD-63B. The diagrams show
the available power budget dependent on number of preamble bits. Please be aware that we
are quoting minimum guaranteed power budget. Experience has shown that the typical values
will be 4dBm higher for 820nm, 3.5dBm
higher for 1300nm and 6dBm higher
for single mode.
Idle line 3 preamble bits Start sending data
(Manchester coded)
16
14
12
10
8
6
4
2
0
0 500 1000 1500 2000 2500 3000 3500 4000 4500
20 bits
preamble
10 bits
preamble
1 bit
preamble
2 bits
preamble
Power budget (dBm)
Transmission speed (kbit/s)
Minimum guaranteed budget 820nm, 62.5/125µm fibre
Minimum guaranteed budget 1300nm, 62.5/125µm fibre
14
12
10
8
6
4
2
0
0 500 1000 1500 2000 2500 3000 3500 4000 4500
20 bits
preamble
10 bits
preamble
1 bit
preamble
2 bits
preamble
Power budget (dBm)
Transmission speed (kbit/s)