Polarization scrambling based on cascaded optical polarization devices having modulated optical retardation
First Claim
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1. 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.
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Abstract
Techniques and devices use cascaded optical polarization devices having modulated optical retardation to control optical polarization of light and can be configured for polarization scrambling. Uniform rate scrambling and quasi-uniform rate scrambling modes are provided in described devices and rate-additive designs based on multiple cascaded devices are also disclosed to achieve high-speed scrambling.
228 Citations
31 Claims
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1. An optical device for controlling optical polarization of light, comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method for controlling optical polarization of light, comprising:
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directing input light through, sequentially, a first optical polarization device configured to have optical birefringence with a first optical axis perpendicular to a propagation direction of the input light, a second optical polarization device configured to have optical birefringence with a second optical axis perpendicular to a propagation direction of received light and at 45 degrees with respect to the first optical axis of the first optical polarization device, a third optical polarization device configured to have optical birefringence with a third optical axis at 45 degrees with respect to the second optical axis of the second optical polarization device, and one or more additional optical polarization devices located downstream from the third optical polarization device and each configured to have an optical axis along the third optical axis; modulating the first optical polarization device at a first modulation frequency to produce a first modulated phase retardation on light output by the first optical polarization device; modulating the second optical polarization device at a second modulation frequency to produce a second modulated phase retardation on light output by the second optical polarization device; modulating the third optical polarization device at a third modulation frequency to produce a third modulated phase retardation on light output by the third optical polarization device; and modulating the one or more additional optical polarization devices located downstream from the third optical polarization device to produce additional phase retardation modulation on light output from the third optical polarization device, wherein one of the first, second and third modulation frequencies is different from the other two of the first, second and third modulation frequencies. - View Dependent Claims (22, 23, 24, 25, 26)
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27. An optical device for controlling optical polarization of light, comprising:
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optical retardation modulators cascaded to form an optical path that receives input light and produces output light, each optical retardation modulator configured to modulate the input light to produce a phase retardation modulation at a modulation frequency and have optical birefringence with a respective optical axis perpendicular to received light, wherein the first three optical retardation modulators at a beginning part of the optical path are arranged to have their optical axes oriented at 45 degrees between two adjacent optical retardation modulators; and a control module coupled to the optical retardation modulators to control phase retardation modulation of the optical retardation modulators, respectively, to produce modulation control signals to the first three optical retardation modulators at the beginning side of the optical path at different modulation frequencies and to control optical retardation modulators downstream from the first three optical retardation modulators to control optical polarization and to additionally modulate optical retardation of the light output from the first three optical retardation modulators to scramble optical polarization of the output light. - View Dependent Claims (28)
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29. A device for controlling optical polarization of light, comprising:
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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 polarization maintaining fiber that directs light to the first optical polarization device where the polarization maintaining fiber is oriented to have a fast or slow optical axis of the polarization maintaining fiber to be at 45 degrees with respect to the first optical axis of 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; and a control module that produces the first and second 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. - View Dependent Claims (30, 31)
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Specification