Page 603 - 5G Basics - Core Network Aspects

Transport aspects 2

7.3.2 Wavelength division multiplexing transmission

Wavelength division multiplexing (WDM) is an optical multiplexing scheme of obtaining a desired optical
signal by combining several modulated optical signals with different central frequencies. Therefore, it is a
kind of FDM in the optical domain. Figure 7-8-a is a schematic block diagram of WDM transmission for
subcarrier signal(s) transmission, where fele and fon (n = 1, 2, …, N) are the central frequencies of
modulating electrical signal and optical carriers, respectively. Here, fele may be different for different
modulating electrical signal. Figure 7-8-b is a schematic block diagram of WDM transmission for equivalent
low-pass (equivalent baseband) signal(s) or digital signal(s) transmission. At first, for both cases, an
electrical signal modulates an optical carrier with an individual E/O converter to generate a modulated
optical signal (RoF signal). The generated RoF signals with different central frequency are combined with a
wavelength MUX to generate a WDM RoF signal. The received WDM RoF signal is put into a wavelength
DEMUX to be divided into N original RoF signals. Each RoF signal is photodetected with an individual O/E
converter to regenerate the original electrical signal.

WDM RoF signal

f
.. .
0 f o1 f o2 f oN
f o1 f o1 – f e le f o1 + f oN – f ele f oN + f o1
f E/O converter #1 f ele f e le O/E converter #1 f
0 f ele f o2 – f ele f o2 + f ele 0 f ele
Wavelenght multiplexer Wavelenght demultiplexer
f o2 f o2
f E/O converter #2 O/E converter #2 f
0 f ele 0 f ele
. .
. .
. .
f oN f oN
f E/O converter #N O/E converter #N f
0 f ele 0 f ele
a)
WDM RoF signal

f o1 .. . f f o1
f E/O converter #1 0 O/E converter #1 f
0 f o1 f o2 f oN 0
W avelenght multiplexer Wavelenght demultiplexer
f o2 f o2
f E/O converter #2 O/E converter #2 f
0 0
. .
. .
. .
f oN f oN
f E/O converter #N O/E converter #N f
0 0
b) G Suppl.55(15)_F7-8

Figure 7-8 – Schematic block diagram of WDM transmission: a) for subcarrier signal(s) transmission; and
b) for equivalent low-pass (equivalent baseband) signal(s) or digital signal(s) transmission

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