Page 51 - Optical Communications Essentials

The Behavior of Light

The Behavior of Light 41

Figure 3.5. Polarization represented as a combina-
tion of a parallel vibration and a perpendicular
vibration.

Figure 3.6. Behavior of an unpolarized light
beam at the interface between air and a non-
metallic surface.

respectively. In the case when all the electric field planes of the different trans-
verse waves are aligned parallel to one another, then the light wave is linearly
polarized. This is the simplest type of polarization.
Unpolarized light can be split into separate polarization components either
by reflection off a nonmetallic surface or by refraction when the light passes
from one material to another. As noted earlier in Fig. 3.1, when an unpolarized
light beam traveling in air impinges on a nonmetallic surface such as glass, part
of the beam is reflected and part is refracted into the glass. A circled dot and an
arrow designate the parallel and perpendicular polarization components,
respectively, in Fig. 3.6. The reflected beam is partially polarized and at a spe-
cific angle (known as Brewster’s angle) is completely perpendicularly polarized.
A familiar example of this is the use of polarizing sunglasses to reduce the glare
of partially polarized sunlight reflections from road or water surfaces. The par-
allel component of the refracted beam is entirely transmitted into the glass,
whereas the perpendicular component is only partially refracted. How much of

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