Optical differential group delay module with folded optical path
First Claim
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1. An optical differential group delay (DGD) device, comprising:
- an input optical port to receive light;
an output optical port to output light;
polarization maintaining retro-reflectors located relative to the input and output optical ports to form a folded optical path that directs light from the input optical port to the output optical port via the polarization maintaining retro-reflectors;
a polarization monitor in the folded optical path to monitor polarization of light;
a plurality of polarization rotators in the folded optical path; and
a plurality of birefringent elements in the folded optical path and separated by the polarization rotators.
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Abstract
Differential group delay (DGD) devices and techniques based on folded optical paths. An in-line polarization monitor can be provided as a feedback for worst-case alignment without using an in-line polarizer. Polarization maintaining retro reflectors can minimize the introduced higher-order polarization effects caused by reflections between folding mirrors or prisms in conventional schemes.
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Citations
20 Claims
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1. An optical differential group delay (DGD) device, comprising:
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an input optical port to receive light; an output optical port to output light; polarization maintaining retro-reflectors located relative to the input and output optical ports to form a folded optical path that directs light from the input optical port to the output optical port via the polarization maintaining retro-reflectors; a polarization monitor in the folded optical path to monitor polarization of light; a plurality of polarization rotators in the folded optical path; and a plurality of birefringent elements in the folded optical path and separated by the polarization rotators. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 19)
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12. An optical differential group delay (DGD) device, comprising:
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an input and output panel; an input optical port that is located on the input and output panel and receives input light; an output optical port that is located on the input and output panel and outputs light; a polarization maintaining retro-reflection module that receives light directed from the input optical port along a first optical path and reflects the received light towards the output optical port along a second optical path while maintaining polarization of the received light, wherein the input optical port, the polarization maintaining retro-reflection module, and the output optical port form a folded optical path; one or more first optical birefringent elements of varying lengths spatially separated from one another and located in series in the first optical path which directs light from the input optical port to the polarization maintaining retro-reflection module; one or more first optical polarization rotators or polarization controllers placed in the first optical path and spatially interleaved with the one or more first optical birefringent elements so that each first optical polarization rotator or polarization controller is adjacent to at least one first birefringent element and is not adjacent to another first optical polarization rotator or polarization controller; one or more second optical birefringent elements of varying lengths spatially separated from one another and located in series in the second optical path which directs light from the polarization maintaining retro-reflection module to the output optical port; and one or more second optical polarization rotators or polarization controllers placed in the second optical path and spatially interleaved with the one or more second optical birefringent elements so that each second optical polarization rotator or polarization controller is adjacent to at least one second birefringent element and is not adjacent to another second optical polarization rotator or polarization controller, wherein the first and second optical birefringent elements and the first and second optical polarization rotators or polarization controllers produce a variable DGD in the light output at the output optical port. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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20. An optical differential group delay (DGD) device, comprising:
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a housing comprising an input and output panel; an input optical port formed on the input and output panel to receive input light; an output optical port formed on the input and output panel to export output light; a first optical path located inside the housing and having a first receiving end linked to the input optical port to receive the received input light and a first output end; a second optical path located inside the housing and having a second receiving end and a second output end linked to the to the output optical port, the second optical path spatially overlapping with at least a portion of the first optical path; a polarization maintaining retro-reflection module that is optically coupled to the first output end of the first optical path to receive light from the first optical path and is optically coupled to the second receiving end of the second optical path to direct light from the first optical path into the second optical path while maintaining polarization of the light, wherein the input optical port, the first optical path, the polarization maintaining retro-reflection module, the second optical path and the output optical port form a folded optical path; a plurality of optical birefringent elements of varying lengths spatially separated from one another and located in series in the first and second optical paths inside the housing, the birefringent elements including a first birefringent element having a DGD value greater than a DGD value of any other birefringent elements and the first birefringent element located closer to the input optical port than any other birefringent elements; one or more optical polarization rotators or polarization controllers placed in the first and second optical paths inside the housing and spatially interleaved with the optical birefringent elements so that each optical polarization rotator or polarization controller is adjacent to at least one birefringent element and is not adjacent to another optical polarization rotator or polarization controller, wherein the optical birefringent elements and the optical polarization rotators or polarization controllers collectively produce a variable DGD in the light output at the output optical port.
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Specification