A liquid crystal polarization rotator device is able to rotate polarization fast
enough to compensate polarization mode dispersion. The amount or degree of rotation
is rapidly reconfigurable. The device includes a cavity filled with a nematic liquid
crystal material. The cavity has electrodes on a first face, e.g., a first substrate,
and electrodes on a second face, e.g., a second substrate, opposite the first face.
The electrodes are shaped and positioned to produce an electric field across the
cavity capable of rotating the alignment direction of the molecules of the liquid
crystal material in the cavity. The electrodes are patterned on the ends of optical
fibers. Aligning and positioning of the electrodes on the ends of the optical fibers
with a predetermined spacing forms the cavity that is filled with the nematic liquid
crystal material. The filled cavity is a so-called liquid crystal microcell wave
plate. A control system is used to control the "rapid" rotation of the alignment
direction of the molecules of the liquid crystal material. The control system receives
data regarding the polarization of light entering or leaving the microcell and
adjusts the direction of the electric field also using trigger pulses such as to
rotate the nematic liquid crystal material molecules by a first predetermined number
of degrees greater than a second desired number of degrees of rotation. Then, the
trigger pulses for the electric field are stopped after the molecules have rotated
by the second desired number of degrees. In this manner, the molecules rotate by
the second desired number of degrees much faster than if a pulse had been applied
with the same speed to rotate them by the second desired number of degrees in he
first place.
