Setting a state of Polarization
Setting the State of Polarization
22
Agilent
8169A
Polarization Controller, Second Edition
Setting the State of Polarization
The state of polarization of a signal can be described by a position on the
Poincare sphere. This position is can be expressed in spherical
coordinates by two angles, called
ε
B
and
θ
p
.
•
θ
p
is the optical angle about the 'equator' of the sphere (that is, 2
θ
p is the
angle of 'longitude').
•
ε
B
is half the angle of elevation from the equatorial plane (that is, 2
ε
B
is the
angle of 'latitude').
Figure 5 The coordinates for describing the state of polarization
The state of polarization is always relative to the output from the polarizing
filter.
There are two ways of setting the state of polarization,
• by specifying the position of the
λ
/4 and
λ
/2 retarder plates, or
• by specifying
ε
B
and
θ
p, the coordinates on the Poincare sphere.