This is unlike RF receivers, where multiple antennas
are used at a great advantage to system performance. Such advantages in RF systems
are derived mostly in cases of non-line-of-sight and point-to-multipoint communications
systems; both of these scenarios do not apply to optical wireless systems as discussed
in this chapter, however.
Receive Field of View (FoV) Field of view (FoV) is the region within which the receiver
can ???see.??? It is the counterpart of beam divergence and is defined by the angle of
the cone (measured in degrees) within which the transmitter has to be located in order
for the receiver to receive the signal. As shown in Figure 9.3, the receiver can see the
transmitter within its FoV, identified by the circle, and thus can receive the signal from
the transmitter within the FoV.
The downside of having a larger FoV may not be apparent until the impact of background
light is considered. By virtue of being able to ???see??? everything within its FoV,
Figure 9.3 Receive optics and receive field of view
The angle defines the
FoV of the receiver.
Field of view
FSO
system
FSO
system
FoV of the FSO receiver
Receive aperture
Detector
(PN diode, APD)
Lens
Receive Optics and Aperture
Receive Field of View
242 Chapter 9
a receiver collects all the light it sees within its FoV.
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