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Tunable compensation for polarization-mode dispersion using a birefringent nonlinearly-chirped bragg grating in a dual-pass configuration
Assignee: University of Southern California
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Filing: 2000-12-01
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Granted: 2002-06-04
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Expires: 2020-12-01
Abstract
Abstract Techniques and devices for compensating polarization-mode dispersion in an optical signal by using a nonlinearly-chirped Bragg grating in a dual-pass configuration.
Inventors
- 👤 Zhongqi Pan
- 👤 Yong Xie
- 👤 Sanggeon Lee
- 👤 Alan E. Willner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 14:11
CPC Classifications
G; G02; G02B; G02B6/00; G02B6/24; G02B6/26; G02B6/27; G02B6/2753; G02B6/278; G02B6/02; G02B6/02057; G02B6/02076; G02B6/0208; G02B6/021; G02B6/02109; G02B6/02195; G02B6/022; G02B6/28; G02B6/293; G02B6/29304; G02B6/29316; G02B6/29317; G02B6/29319; G02B6/2932; G02B6/29379; G02B6/29395; H; H04; H04B; H04B10/00; H04B10/25; H04B10/2507; H04B10/2569; G02B6/29302
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
262 words
An optical fiber device, comprising: a first optic fiber to transport optical energy and to exhibit optical birefringence for light polarizations along first and second polarization axes that are substantially perpendicular to said first fiber; a fiber grating formed between a first location and a second location in said first fiber to have a periodic spatial pattern that changes nonlinearly with a position along said first fiber to effectuate different relative delays in reflected optical spectral components of a common polarization of different wavelengths at different positions along said fiber grating that meet Bragg conditions and different relative delays between two reflected optical components of different light polarizations respectively along said first and second polarization axes at a common wavelength, said fiber grating operable to interact with an input optical signal traveling from said first location towards said second location in said first fiber to produce a first optical signal by reflection in a direction from said second location towards said first location; a second fiber having a first distal end coupled to said first fiber at a position to receive said first optical signal through said first location, and a second distal end coupled to said first fiber at a different position to direct said first optical signal back into said fiber grating at said second location, wherein said fiber grating operates to reflect said first optical signal to produce an output optical signal directing from said first location towards said second location; and a polarization rotator coupled in said second fiber to rotate a light polarization by about 90 degrees.
Claim 2
Dependent Claim
262 words
An optical fiber device, comprising: a first optic fiber to transport optical energy and to exhibit optical birefringence for light polarizations along first and second polarization axes that are substantially perpendicular to said first fiber; a fiber grating formed between a first location and a second location in said first fiber to have a periodic spatial pattern that changes nonlinearly with a position along said first fiber to effectuate different relative delays in reflected optical spectral components of a common polarization of different wavelengths at different positions along said fiber grating that meet Bragg conditions and different relative delays between two reflected optical components of different light polarizations respectively along said first and second polarization axes at a common wavelength, said fiber grating operable to interact with an input optical signal traveling from said first location towards said second location in said first fiber to produce a first optical signal by reflection in a direction from said second location towards said first location; a second fiber having a first distal end coupled to said first fiber at a position to receive said first optical signal through said first location, and a second distal end coupled to said first fiber at a different position to direct said first optical signal back into said fiber grating at said second location, wherein said fiber grating operates to reflect said first optical signal to produce an output optical signal directing from said first location towards said second location; and a polarization rotator coupled in said second fiber to rotate a light polarization by about 90 degrees.
Claim 3
Dependent Claim
54 words
The device as in claim 1 , further comprising an input fiber coupled to said first fiber to direct said input optical signal into said fiber grating through said first location, and an output fiber coupled to said first fiber to receive said output optical signal from said fiber grating through said second location.
Claim 4
Dependent Claim
125 words
The device as in claim 2 , further comprising: a first optical circulator to couple said input fiber, a first distal end of said first fiber near said first location, and said first distal end of said second fiber together to direct said input signal from said input fiber into said fiber grating and said first optical signal from said fiber grating into said second fiber; and a second optical circulator to couple said output fiber, a second distal end of said first fiber near said second location, and said second distal end of said second fiber together to direct said first optical signal from said second fiber into said fiber grating and said output optical signal from said fiber grating into said output fiber.
Claim 5
Dependent Claim
25 words
The device as in claim 2 , further comprising a polarization controller in said input fiber to control a polarization in said input optical signal.
Claim 6
Dependent Claim
50 words
The device as in claim 1 , further comprising a grating control unit coupled to said first fiber and operable to change a property of said periodic spatial pattern of said fiber grating to vary relative time delays of different spectral components in said first and said output optical signals.
Claim 7
Dependent Claim
21 words
The device as in claim 5 , wherein said grating control is operable to change a length of said first fiber.
Claim 8
Dependent Claim
70 words
The device as in claim 5 , further comprising a dispersion detection unit coupled to receive a fraction of said output optical signal and to measure an amount of dispersion in said output signal to produce a control signal, and wherein said grating control unit is operable to change said property of said periodic spatial pattern in according to said control signal to reduce said dispersion in said output signal.
Claim 9
Dependent Claim
19 words
The device as in claim 7 , wherein said dispersion detection unit is operable to measure a polarization-mode dispersion.
Claim 10
Dependent Claim
38 words
The device as in claim 1 , wherein said periodic spatial pattern includes a modulation in a refractive index of said first fiber whose spatial period nonlinearly decreases or increases from said first location to said second location.
Claim 11
Independent Claim
248 words
A method for compensating for optical dispersion in an input optical signal, comprising: directing the input optical signal into a first optic fiber through a first distal end to propagate towards a second distal end, said first fiber configured to exhibit optical birefringence for light polarizations along first and second polarization axes that are substantially perpendicular to said first fiber, said first fiber further configured to have a fiber grating formed between a first location near said first distal end and a second location near said second distal end to have a periodic spatial pattern that changes nonlinearly with a position along said first fiber to effectuate different relative delays in reflected optical spectral components of a common polarization of different wavelengths at different positions along said fiber grating that meet Bragg conditions and different relative delays between two reflected optical components of different light polarizations respectively along said first and second polarization axes at a common wavelength; directing a reflected optical signal in a direction from said second location towards said first location generated by reflection of said input optical signal in said fiber grating outside said fiber grating; rotating each polarization in said reflected optical signal by about 90 degrees to produce a polarization-rotated reflected optical signal; and directing said polarization-rotated reflected optical signal back into said fiber grating to travel from said first location towards said second location in said first fiber to produce an output signal from reflection of said polarization-rotated reflected optical signal.
Claim 12
Independent Claim
248 words
A method for compensating for optical dispersion in an input optical signal, comprising: directing the input optical signal into a first optic fiber through a first distal end to propagate towards a second distal end, said first fiber configured to exhibit optical birefringence for light polarizations along first and second polarization axes that are substantially perpendicular to said first fiber, said first fiber further configured to have a fiber grating formed between a first location near said first distal end and a second location near said second distal end to have a periodic spatial pattern that changes nonlinearly with a position along said first fiber to effectuate different relative delays in reflected optical spectral components of a common polarization of different wavelengths at different positions along said fiber grating that meet Bragg conditions and different relative delays between two reflected optical components of different light polarizations respectively along said first and second polarization axes at a common wavelength; directing a reflected optical signal in a direction from said second location towards said first location generated by reflection of said input optical signal in said fiber grating outside said fiber grating; rotating each polarization in said reflected optical signal by about 90 degrees to produce a polarization-rotated reflected optical signal; and directing said polarization-rotated reflected optical signal back into said fiber grating to travel from said first location towards said second location in said first fiber to produce an output signal from reflection of said polarization-rotated reflected optical signal.
Claim 13
Dependent Claim
40 words
The method as in claim 10 , further comprising changing a property of said periodic spatial pattern of said fiber grating to vary relative time delays of different spectral components in said reflected optical signal and said output optical signal.
Claim 14
Dependent Claim
22 words
The method as in claim 11 , wherein said property of said periodic spatial pattern includes a length of said fiber grating.
Claim 15
Dependent Claim
40 words
The method as in claim 11 , further comprising: measuring an amount of optical dispersion in said output optical signal; and adjusting said property of said periodic spatial pattern according to the measured optical dispersion to reduce said optical dispersion.
Claim 16
Dependent Claim
15 words
The method as in claim 13 , wherein said optical dispersion includes a polarization-mode dispersion.
Claim 17
Dependent Claim
118 words
An optical device, comprising: a grating adapted to have a periodic spatial pattern that changes nonlinearly with a position along an optical path from a first grating distal end to a second grating distal end along said grating and to have different refractive indices for light polarizations along first and second polarization axes that are substantially perpendicular to said optical path; an optical wave-guiding path having a first distal end coupled to receive light from said first grating distal end and a second distal end coupled to direct said light to said second grating distal end; and a polarization rotator coupled in said optical wave-guiding path to rotate a light polarization of said light by about 90 degrees.
Claim 18
Dependent Claim
118 words
An optical device, comprising: a grating adapted to have a periodic spatial pattern that changes nonlinearly with a position along an optical path from a first grating distal end to a second grating distal end along said grating and to have different refractive indices for light polarizations along first and second polarization axes that are substantially perpendicular to said optical path; an optical wave-guiding path having a first distal end coupled to receive light from said first grating distal end and a second distal end coupled to direct said light to said second grating distal end; and a polarization rotator coupled in said optical wave-guiding path to rotate a light polarization of said light by about 90 degrees.
Claim 19
Dependent Claim
85 words
The device as in claim 15 , further comprising a grating control unit coupled to change a property of said grating to alter a relative delay between two spectral components of different wavelengths in an optical signal, wherein said optical signal is directed to said grating for the first time from the first grating distal end, and, after passing through the polarization rotator in the said optical wave-guiding path, is then directed into the grating for the second time from the second grating distal end.
Claim 20
Dependent Claim
20 words
The device as in claim 16 , wherein said property of said grating includes an overall length of said grating.
Claim 21
Dependent Claim
39 words
The device as in claim 16 , wherein said grating control unit is operable to change said property differently in response to different measurements of optical dispersion in an output optical signal generated from said second grating distal end.
Claim 22
Dependent Claim
16 words
The device as in claim 15 , wherein said grating is formed in a birefringent fiber.
Claim 23
Dependent Claim
17 words
The device as in claim 15 , wherein said grating includes a waveguide fabricated over a substrate.
Claim 24
Dependent Claim
29 words
The device as in claim 15 , wherein said optical wave-guiding path includes a fiber that is configured to preserve a state of polarization of a beam propagating therein.
Claim 25
Independent Claim
146 words
A method, comprising: directing an optical signal into a first grating distal end of a fiber grating adapted to have a periodic spatial pattern that changes nonlinearly with a position from the first grating distal end to a second grating distal end along said fiber grating and to have different refractive indices for light polarizations along first and second polarization axes that are substantially perpendicular to said fiber grating; receiving a first reflected optical signal from the first grating distal end that is produced by the fiber grating by reflecting the optical signal; rotating a light polarization of the first reflected optical signal by about 90 degrees to produce a rotated first reflected optical signal; and directing the rotated first reflected optical signal into the fiber grating from the second grating distal end to produce a second reflected optical signal at the second grating distal end.
Claim 26
Independent Claim
146 words
A method, comprising: directing an optical signal into a first grating distal end of a fiber grating adapted to have a periodic spatial pattern that changes nonlinearly with a position from the first grating distal end to a second grating distal end along said fiber grating and to have different refractive indices for light polarizations along first and second polarization axes that are substantially perpendicular to said fiber grating; receiving a first reflected optical signal from the first grating distal end that is produced by the fiber grating by reflecting the optical signal; rotating a light polarization of the first reflected optical signal by about 90 degrees to produce a rotated first reflected optical signal; and directing the rotated first reflected optical signal into the fiber grating from the second grating distal end to produce a second reflected optical signal at the second grating distal end.
Claim 27
Dependent Claim
31 words
The method as in claim 22 , further comprising changing a length of said fiber grating to change relative delays of different spectral components at different wavelengths in said optical signal.
Claim 28
Dependent Claim
90 words
The method as in claim 22 , wherein a polarization rotator is used to produce the rotated first reflected signal, and further comprising: preserving a state of polarization of the first reflected optical signal when directing the first reflected optical signal from the first grating distal end of the fiber grating to the polarization rotator; and preserving a state of polarization of the rotated first reflected optical signal when directing the rotated first reflected optical signal from the polarization rotator to the second grating distal end of the fiber grating.
References Cited (Backward Citations)
US5982963A
Cited
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