US3569996A
Expired / Lapsed
US
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Optical heterodyne receiver with pulse widening or stretching
Assignee: AT&T Inc
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Filing: 1968-06-07
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Granted: 1971-03-09
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Expires: 1988-06-07
Abstract
Abstract In the optical heterodyne receivers disclosed, the overall signal-to-noise ratio is improved by widening in terms of time duration the information-modulated optical pulses so that their bandwidth is comparable to the bandwidth of the detector. In particular, multiple reflection widening techniques are disclosed. Balanced detection with pulse widening in each path is also disclosed.
Inventors
- 👤 James E Goell
- 👤 William M Hubbard
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 10:56
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/60; G; G02; G02F; G02F2/00; G02F2/002; H04B10/61; H04B10/64
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
44 words
A receiver for modulated pulses of optical radiation, comprising partially reflective means intercepting said pulses for widening said pulses in terms of time duration, means for down-converting the carrier frequency of said pulses, and means for detecting said pulses at said down converted frequency.
Claim 2
Dependent Claim
44 words
A receiver for modulated pulses of optical radiation, comprising partially reflective means intercepting said pulses for widening said pulses in terms of time duration, means for down-converting the carrier frequency of said pulses, and means for detecting said pulses at said down converted frequency.
Claim 3
Dependent Claim
52 words
A receiver according to claim 1 in which the means for down converting the pulses includes means for combining the received modulated pulses with optical pulses of differing frequency before said modulated pulses are intercepted by the widening means, and means for mixing the combined pulses after widening by said widening means.
Claim 4
Dependent Claim
32 words
A receiver according to claim 1 in which the widening means comprises an interferometer adapted for oblique injection of the received modulated pulses, said interferometer having an output reflector of graded reflectivity.
Claim 5
Dependent Claim
25 words
A receiver according to claim 3 in which the interferometer is adapted for lateral displacements of portions of the beams in more than one direction.
Claim 6
Dependent Claim
77 words
A receiver according to claim 3 in which the angle of injection into the interferometer and the graded reflectivity of the output reflector are mutually adapted to provide a relative delay of adjacent portions of the transmitted optical pulse energy, which delay is equal to an integral multiple of the period of a selected intermediate frequency, the down converting means including a local source of pulses differing in frequency from said received pulses by said intermediate frequency.
Claim 7
Dependent Claim
48 words
A receiver according to claim 1 in which the widening means comprises a multiple internal reflection prism having an aperture adapted for admission of the received pulses and for output transmission of only a portion of the pulse energy during each multiple internal reflection circuit of said pulses.
Claim 8
Dependent Claim
92 words
A receiver according to claim 6 in which the down converting means includes means for combining the received modulated pulses with optical pulses of a second frequency different from the frequency of the received pulses and in which the dimensions of the prism are adapted to provide a relative delay of different portions of the transmitted optical pulse energy, which delay is equal to an integral multiple of the period of the difference frequency, where the difference frequency is equal to the difference of the received pulse frequency and the second frequency.
Claim 9
Dependent Claim
96 words
A receiver according to claim 1 in which the down converting means includes a local pulse source, means for combining pulses from said first local source with the received pulses in first and second paths, the pulse-widening means including first and second multiple reflection pulse stretchers intercepting said combined pulses in said first and second paths, the down converting and detecting means further including balanced means for combining the outputs of said first and second pulse stretchers in a balanced manner, said received pulses and said pulses from said local source having like pulse widths initially.
Claim 10
Dependent Claim
25 words
A receiver according to claim 8 in which said first and second pulse stretchers each include a pair of interferometers tilted in mutually orthogonal coordinates.
Claim 11
Dependent Claim
48 words
A receiver according to claim 8 in which said first and second pulse stretchers each include an interferometer including a curved reflector and an optical axis, said interferometer being adapted for injection of the combined pulses in a direction that is skew with respect to said optical axis.
References Cited (Backward Citations)
US2721259A
Cited
US3482099A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-03-08 | 1974-09-07 | 1975-03-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-03-08 | 1978-09-07 | 1979-03-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-03-08 | 1982-09-07 | 1983-03-09 | $7700.00 | Window Closed / Lapsed |