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USH474H
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Optical transversal fiber with reflective taps
Assignee: United States Department of the Navy
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Filing: 1985-10-25
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Granted: 1988-06-07
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Expires: 2005-10-25
Abstract
Abstract A method and means for forming an optical transversal filter and the optical transversal filter itself. The optical transversal filter comprises an optical fiber with a plurality of short reflective phase gratings disposed therein, with each reflective phase grating comprising a periodic variation of the refractive index of the optical fiber. These reflective phase gratings are disposed at predetermined positions along the length of the optical fiber and each reflective phase grating has a predetermined reflectance in order to reflect a predetermined relative amplitude of the light propagating in a first direction within the optical fiber to thereby counterpropagate back along the optical fiber. Modulated light source means are provided for directing light into one end of the optical fiber, and means for detecting light are provided to detect the light reflected by the plurality of reflective phase gratings. The predetermined positions of the plurality of reflective phase gratings and the individual reflectances of the plurality of reflective phase gratings are set in order that the light reflected by each of the reflective phase gratings is summed in light detecting means to yield a desired transversal filter function. The reflective phase gratings are written into the optical fiber core by means of two short counterpropagating coherent light pulses. The precise locations of these reflective phase gratings are determined by changing the optical length that either the forward-propagating or the counterpropagating pulse must traverse, thereby changing the location where these two pulses overlap in the optical fiber.
Inventors
- 👤 Henry F. Taylor
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 23:34
CPC Classifications
G; G02; G02B; G02B6/00; G02B6/02; G02B6/02057; G02B6/02076; G02B6/02123; G02B6/02128; G02B6/24; G02B6/26; G02B6/28; G02B6/2804; G02B6/2861; G02B6/293; G02B6/29304; G02B6/29316; G02B6/29317
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
260 words
An optical transversal filter capable of a very high bandwidth, comprising: an optical fiber for propagating light, said optical fiber having a first and second ends and a core made from a core material which has a non-linear intersection with light such that a grating is formed at certain light amplitudes; coherent light source means for providing, for a predetermined period of time, coherent light pulses to propagate in said optical fiber in a first direction therein; means for causing said coherent light pulses to counterpropagate in said optical fiber in a direction opposite to said first direction to thereby interfere with said pulses propagating in said first direction such that a first reflective phase grating with a wide reflective bandwidth is formed at a location in said optical fiber where said propagating and counterpropagating pulses overlap; means for changing the location where said propagating and counterpropagating pulses overlap in said optical fiber to thereby form additional reflective phase gratings at different predetermined locations in said optical fiber, with the total amplitude of the coherent light pulses utilized to form each different reflective phase grating being adjusted to provide desired reflectance values; modulated light source means for providing light which is to be operated on by said transversal filter to propagate in said optical fiber and then to be reflected back along said optical fiber by said first and additional reflective phase gratings in accordance with the desired reflectance values of those reflective phase gratings; and means for detecting said light reflected back by said first and additional phase gratings.
Claim 2
Dependent Claim
260 words
An optical transversal filter capable of a very high bandwidth, comprising: an optical fiber for propagating light, said optical fiber having a first and second ends and a core made from a core material which has a non-linear intersection with light such that a grating is formed at certain light amplitudes; coherent light source means for providing, for a predetermined period of time, coherent light pulses to propagate in said optical fiber in a first direction therein; means for causing said coherent light pulses to counterpropagate in said optical fiber in a direction opposite to said first direction to thereby interfere with said pulses propagating in said first direction such that a first reflective phase grating with a wide reflective bandwidth is formed at a location in said optical fiber where said propagating and counterpropagating pulses overlap; means for changing the location where said propagating and counterpropagating pulses overlap in said optical fiber to thereby form additional reflective phase gratings at different predetermined locations in said optical fiber, with the total amplitude of the coherent light pulses utilized to form each different reflective phase grating being adjusted to provide desired reflectance values; modulated light source means for providing light which is to be operated on by said transversal filter to propagate in said optical fiber and then to be reflected back along said optical fiber by said first and additional reflective phase gratings in accordance with the desired reflectance values of those reflective phase gratings; and means for detecting said light reflected back by said first and additional phase gratings.
Claim 3
Dependent Claim
119 words
An optical transversal filter as defined in claim 1, wherein said means for causing said coherent light to counterpropagate comprises: a first optical path; a reflector at one end of said optical path for reflecting light propagating in said optical path into said second end of said optical fiber; a first beamsplitter for dividing the coherent light pulse from said coherent light source means into a first and second components and directing said first component into said first end of said optical fiber and directing said second component to propagate in said first optical path toward said optical reflector, wherein light reflected from said optical reflector is directed into said second end of said optical fiber to counterpropagate therein.
Claim 4
Dependent Claim
26 words
An optical transversal filter as defined in claim 2, wherein said coherent light source means includes a laser which is adjustable to provide different amplitude pulses.
Claim 5
Dependent Claim
59 words
An optical transversal filter as defined in claim 3, wherein said means for changing the location where said pulses overlap comprises optical path length changing means for adjusting the optical length of said first optical path to cause said propagating and counterpropagating pulses to overlap and form said reflective phase gratings at said predetermined locations in said optical fiber.
Claim 6
Dependent Claim
33 words
An optical transversal filter as defined in claim 4, wherein said optical path length changing means comprises means for moving said reflector to increase or decrease the length of said first optical path.
Claim 7
Dependent Claim
124 words
An optical transversal filter as defined in claim 1, wherein said coherent light source means comprises means for generating a first and second consecutive light pulses separated in time by a predetermined amount in order to form a reflective phase grating; and wherein said means for causing said coherent light to counterpropagate comprises a reflector disposed at approximately said second end of said optical fiber; wherein said first light pulse is reflected by said reflector so that it counterpropagates in said optical fiber and overlaps with said propagating second light pulse to form said reflective phase grating, with the location of said reflective phase grating being determined by said predetermined time separation between said first and second pulses and the location of said reflector.
Claim 8
Dependent Claim
33 words
An optical transversal filter as defined in claim 6, wherein said location changing means comprises means for changing the optical path length that said first light pulse must traverse before reaching said reflector.
Claim 9
Dependent Claim
44 words
An optical transversal filter as defined in claim 7, wherein said optical path changing means includes means for moving said reflector toward or away from the second end of said optical fiber to thereby change the location where the propagating and counterpropagating pulses overlap.
Claim 10
Dependent Claim
44 words
An optical transversal filter as defined in claim 6, wherein said location changing means includes means for changing said predetermined time amount separating said first and second light pulses to thereby cause said propagating and counterpropagating pulses to overlap at a different predetermined location.
Claim 11
Dependent Claim
56 words
An optical transversal filter as defined in claim 9, wherein said coherent light source means comprises: a laser; means for directing light from said laser into said first end of said optical fiber; and a shutter disposed between said laser and said directing means for controlling when said laser light is directed into said optical fiber.
Claim 12
Dependent Claim
200 words
An optical transversal filter capable of very high bandwidth operation comprising: an optical fiber for propagating light, said optical fiber including a plurality of short reflective phase gratings each having a wide reflective bandwidth, with each reflective phase grating comprising a periodic variation of the refractive index of said optical fiber, said reflective phase gratings being disposed at predetermined positions along the length of said optical fiber and with each reflective phase grating having a predetermined reflectance in order to reflect a predetermined relative amplitude of light propagating in a first direction within said optical fiber to thereby counterpropagate back along said optical fiber; modulated light source means for directing light into one end of said optical fiber to propagate in said first direction; and means for detecting light reflected by said plurality of reflective phase gratings back along said optical fiber; wherein said predetermined positions of said plurality of reflective phase gratings and the individual reflectances of said plurality of reflective phase gratings are set in order that the light reflected by each of said reflective phase gratings to counterpropagate back along said optical fiber is summed by said light detecting means to yield a desired transversal filter function.
Claim 13
Dependent Claim
200 words
An optical transversal filter capable of very high bandwidth operation comprising: an optical fiber for propagating light, said optical fiber including a plurality of short reflective phase gratings each having a wide reflective bandwidth, with each reflective phase grating comprising a periodic variation of the refractive index of said optical fiber, said reflective phase gratings being disposed at predetermined positions along the length of said optical fiber and with each reflective phase grating having a predetermined reflectance in order to reflect a predetermined relative amplitude of light propagating in a first direction within said optical fiber to thereby counterpropagate back along said optical fiber; modulated light source means for directing light into one end of said optical fiber to propagate in said first direction; and means for detecting light reflected by said plurality of reflective phase gratings back along said optical fiber; wherein said predetermined positions of said plurality of reflective phase gratings and the individual reflectances of said plurality of reflective phase gratings are set in order that the light reflected by each of said reflective phase gratings to counterpropagate back along said optical fiber is summed by said light detecting means to yield a desired transversal filter function.
Claim 14
Independent Claim
207 words
A method for forming an optical fiber for use as a transversal filter, comprising the steps of: generating and adjusting a coherent light source to provide light pulses of a predetermined width and a predetermined amplitude; causing said coherent light pulses to propagate in a first direction and to counterpropagate back in a direction opposite to said first direction in an optical fiber having a core made from a material which has a non-linear interaction with light, such that a short periodic variation of the refractive index of the optical fiber, i.e., a reflective phase grating, is formed having a wide reflective bandwidth at a localized position in said optical fiber where said propagating and counterpropagating pulses overlap; and changing the location where said propagating and counterpropagating pulses overlap in said optical fiber to thereby form additional reflective phase gratings at different predetermined locations in said optical fiber, and with each new location, changing the total light amplitude at said new location from said overlapping coherent light pulses to provide a desired reflectance value for the reflective phase grating at this new location, such that light reflected from each of said reflective phase gratings at their predetermined reflectances will yield a desired transversal filter function when summed.
Claim 15
Independent Claim
207 words
A method for forming an optical fiber for use as a transversal filter, comprising the steps of: generating and adjusting a coherent light source to provide light pulses of a predetermined width and a predetermined amplitude; causing said coherent light pulses to propagate in a first direction and to counterpropagate back in a direction opposite to said first direction in an optical fiber having a core made from a material which has a non-linear interaction with light, such that a short periodic variation of the refractive index of the optical fiber, i.e., a reflective phase grating, is formed having a wide reflective bandwidth at a localized position in said optical fiber where said propagating and counterpropagating pulses overlap; and changing the location where said propagating and counterpropagating pulses overlap in said optical fiber to thereby form additional reflective phase gratings at different predetermined locations in said optical fiber, and with each new location, changing the total light amplitude at said new location from said overlapping coherent light pulses to provide a desired reflectance value for the reflective phase grating at this new location, such that light reflected from each of said reflective phase gratings at their predetermined reflectances will yield a desired transversal filter function when summed.
Claim 16
Dependent Claim
96 words
A method as defined in claim 12, wherein said causing step includes the steps of, for each individual reflective phase grating to be formed: splitting a single short coherent light pulse into a first and second components; directing said first light pulse component into one end of said optical fiber to propagate therein in said first direction, and directing said second light pulse component into the opposite end of said optical fiber to counterpropagate in said opposite direction therein; wherein one of said first or second light pulse components are directed through a variable optical path.
Claim 17
Dependent Claim
47 words
A method as defined in claim 13, wherein said location changing step comprises the step of changing the optical length of said variable optical path by a predetermined amount to thereby change the location where said propagating and counterpropagating pulses overlap and form said reflective optical grating.
Claim 18
Dependent Claim
26 words
A method as defined in claim 14, wherein said optical length changing step comprises the step of moving a mirror disposed in said variable optical path.
Claim 19
Dependent Claim
139 words
A method as defined in claim 12, wherein said causing step comprises the step of, for each individual reflective phase grating to be formed: directing a first light pulse into one end of said optical fiber to propagate said first direction therethrough; directing a second light pulse into said one end of said optical fiber at a predetermined time after said first light pulse to propagate in said first direction therein; reflecting said first light pulse to counterpropagate in said optical fiber; wherein said reflective phase grating is formed in said optical fiber where said first counterpropagating light pulse and said second propagating light pulse overlap, with the location of said reflective phase grating being determined by said predetermined time between said first and second light pulses and by the optical path length that said first pulse must traverse.
Claim 20
Dependent Claim
27 words
A method as defined in claim 16, wherein said location changing step comprises the step of changing the optical path length that said first pulse must traverse.
Claim 21
Dependent Claim
59 words
A method as defined in claim 16, wherein said location changing step comprises the step of disposing a reflector close to the other end of said optical fiber from said one end, and moving said reflector toward or away from said other end by a predetermined amount to thereby change the location where said first and second pulses overlap.
Claim 22
Dependent Claim
38 words
A method as defined in claim 16, wherein said location changing step comprises the step of changing said predetermined time between said first and second pulses to thereby change the location where said first and second pulses overlap.
Claim 23
Dependent Claim
74 words
A method as defined in claim 16, further comprising the steps of: directing modulated light to be operated on by said transversal filter to propagate in said optical fiber and then to be reflected back along said optical fiber by said reflective phase gratings in accordance with the predetermined reflectances of those reflective phase gratings; and detecting said light reflected by all of said reflective phase gratings to obtain said desired transversal filter function.
Claim 24
Dependent Claim
74 words
A method as defined in claim 14 further comprising the steps of: directing modulated light to be operated on by said transversal filter to propagate in said optical fiber and then to be reflected back along said optical fiber by said reflective phase gratings in accordance with the predetermined reflectances of those reflective phase gratings; and detecting said light reflected by all of said reflective phase gratings to obtain said desired transversal filter function.
Claim 25
Independent Claim
160 words
A method for obtaining a transversal filter function, comprising the steps of: directing modulated light into an optical fiber which contains a plurality of short wideband reflective phase gratings formed in the fiber core thereof, with each reflective phase grating comprising a periodic variation of the refractive index of said optical fiber, said reflective phase gratings being disposed at predetermined positions along the length of said optical fiber and with each reflective phase grating having a predetermined reflectance in order to reflect a predetermined relative portion of the amplitude of said modulated light back along said fiber; and detecting the modulated light reflected by said plurality of reflective phase gratings; wherein said predetermined positions of said plurality of reflective phase gratings and the predetermined reflectances of said plurality of reflective phase gratings are chosen such that the sum of all of the light reflected by said reflective phase gratings detected in said detecting step yields a desired transversal filter function.
Claim 26
Independent Claim
160 words
A method for obtaining a transversal filter function, comprising the steps of: directing modulated light into an optical fiber which contains a plurality of short wideband reflective phase gratings formed in the fiber core thereof, with each reflective phase grating comprising a periodic variation of the refractive index of said optical fiber, said reflective phase gratings being disposed at predetermined positions along the length of said optical fiber and with each reflective phase grating having a predetermined reflectance in order to reflect a predetermined relative portion of the amplitude of said modulated light back along said fiber; and detecting the modulated light reflected by said plurality of reflective phase gratings; wherein said predetermined positions of said plurality of reflective phase gratings and the predetermined reflectances of said plurality of reflective phase gratings are chosen such that the sum of all of the light reflected by said reflective phase gratings detected in said detecting step yields a desired transversal filter function.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-06-07 | 1991-12-07 | 1992-06-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-06-07 | 1995-12-07 | 1996-06-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-06-07 | 1999-12-07 | 2000-06-07 | $7700.00 | Window Closed / Lapsed |