Patent ID: 8780433

Claim:
An optical device for controlling optical polarization of light, comprising: a first optical polarization device that receives input light and is configured to have optical birefringence with a first optical axis perpendicular to a propagation direction of the input light, the first optical polarization device configured to operate on light to produce a first phase retardation on output light that varies with a first control signal applied to the first optical polarization device; a second optical polarization device located downstream from the first optical polarization device and configured to have optical birefringence with a second optical axis at 45 degrees with respect to the first optical axis and perpendicular to the propagation direction of received light, the second optical polarization device configured to operate on light to produce a second phase retardation on output light that varies with a second control signal applied to the second optical polarization device; a third optical polarization device located downstream from the second optical polarization device and configured to have optical birefringence with a third optical axis at 45 degrees with respect to the second optical axis and perpendicular to the propagation direction of received light, the third optical polarization device configured to operate on light to produce a third phase retardation on output light that varies with a third control signal applied to the third optical polarization device; one or more additional optical polarization devices located downstream from the third optical polarization device and each configured to have optical birefringence with an optical axis along the third optical axis, each additional optical polarization device configured to operate on light to produce a respective phase retardation on output light that varies with a respective additional control signal applied to the additional optical polarization device; and a control module that produces the first, second, third and one or more additional control signals and modulates each control signal at a respective modulation frequency to vary a respective phase retardation on respective output light produced by a respective optical polarization device, wherein one of the first, second and third control signals is different in modulation frequency from the other two of the first, second and third control signals.