US5023948A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Polarization modulation of optical signals using birefringent medium
Assignee: British Telecommunications PLC
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Filing: 1989-03-01
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Granted: 1991-06-11
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Expires: 2009-03-01
Abstract
Abstract A digital transmission system and method for coherent optical systems in which a source signal is frequency modulated by digital information and caused to be incident on a birefringent medium. Moudulation signals are produced having a polarization which is dependent on the frequency of the source signal. The information can be regenerated by processing only one of the modulation signals and thus only one need be transmitted. Further modulation signals may be transmitted to enable error checking at the receiver.
Inventors
- 👤 David W. Smith
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 17:45
CPC Classifications
H; H04; H04B; H04B14/00; H04B14/002; H04B14/008; H04B10/00; H04B10/50; H04B10/516; H04B10/532
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
66 words
A method of transmitting digital information comprising: frequency modulating a polarized electromagnetic signal in response to said information to produce a frequency modulated electromagnetic signal causing said frequency modulated electromagnetic signal to be incident on a birefringent medium so as to generate a polarization modulated signal having a polarization which corresponds to the frequency of said frequency modulated electromagnetic signal; and transmitting said polarization modulated signal.
Claim 2
Independent Claim
66 words
A method of transmitting digital information comprising: frequency modulating a polarized electromagnetic signal in response to said information to produce a frequency modulated electromagnetic signal causing said frequency modulated electromagnetic signal to be incident on a birefringent medium so as to generate a polarization modulated signal having a polarization which corresponds to the frequency of said frequency modulated electromagnetic signal; and transmitting said polarization modulated signal.
Claim 3
Dependent Claim
42 words
A method as in claim 1 wherein said frequency modulated signal includes signals at first and second frequencies thereby producing corresponding first and second polarization modulated signals and further comprising detecting said information from at least one of said polarization modulated signals.
Claim 4
Dependent Claim
26 words
A method as in claim 2 wherein said detecting step includes determining changes in at least one of said polarization modulated signals to regenerate said information.
Claim 5
Dependent Claim
20 words
A method as in claim 3 wherein said information is detected from at least one of said polarization modulated signals.
Claim 6
Dependent Claim
58 words
A method as in claim 4 wherein two polarization modulated signals are generated and said method further comprises transmitting and processing said two polarization modulated signals to generate two respective streams of digital data therefrom, and comparing said streams to regenerate said digital information and determine if an error has occurred in the regeneration of said digital information.
Claim 7
Dependent Claim
29 words
A method as in claim 5 wherein said frequency modulated electromagnetic signal is caused to be incident on said birefringent medium at π/4 to the axis of said medium.
Claim 8
Dependent Claim
54 words
A method as in claim 6 wherein said detecting step includes causing said two polarization modulated signals to interfere with a polarized local oscillator signal of predetermined frequency so as to generate two respective intermediate frequency signals, both having frequencies which full within an intermediate frequency band of means for performing said detecting step.
Claim 9
Dependent Claim
29 words
A method as in claim 1, 2, 3, 4, 5, 6 or 7 further comprising modulating the amplitude and/or phase of said electromagnetic signal in response to digital information.
Claim 10
Dependent Claim
25 words
A method as in claim 1, 2, 3, 4, 5, 6, or 7 wherein said frequency modulated electromagnetic and polarization modulated signals are optical signals.
Claim 11
Dependent Claim
90 words
A digital information transmission system comprising: means for modulating a polarized electromagnetic signal in response to said information to produce a frequency modulated electromagnetic signal at an output thereof; means for transmitting a polarization modulated electromagnetic signal including a birefringent medium which is coupled to said output of said means for modulating; means for causing said frequency modulated electromagnetic signal to be incident on said birefringent medium so as to generate a polarization modulated signal having a polarization which is dependent on the frequency of said frequency modulated electromagnetic signal.
Claim 12
Dependent Claim
90 words
A digital information transmission system comprising: means for modulating a polarized electromagnetic signal in response to said information to produce a frequency modulated electromagnetic signal at an output thereof; means for transmitting a polarization modulated electromagnetic signal including a birefringent medium which is coupled to said output of said means for modulating; means for causing said frequency modulated electromagnetic signal to be incident on said birefringent medium so as to generate a polarization modulated signal having a polarization which is dependent on the frequency of said frequency modulated electromagnetic signal.
Claim 13
Dependent Claim
48 words
A system as in claim 10 wherein said frequency modulated signal includes at first and second frequencies thereby producing corresponding first and second polarization modulated signals and further comprising means, coupled to said transmitting means, for detecting said information from at least one of said polarization modulated signals.
Claim 14
Dependent Claim
25 words
A system as in claim 11 wherein said detecting means detects changes in at least one of said polarization modulated signals to regenerate said information.
Claim 15
Dependent Claim
24 words
A system as in claim 11 or 12 wherein said detecting means detects said information from at least one of said polarization modulated signals.
Claim 16
Dependent Claim
61 words
A system as in claim 13 wherein two polarization modulated signals are generated in said birefringent medium and said detecting means is adapted to process said two polarization modulated signals to generate two respective streams of digital data therefrom and compare said streams to regenerate said digital information and determine if an error has occurred in the regeneration of said information.
Claim 17
Dependent Claim
50 words
A system as in claim 14 wherein said detecting means causes said two polarization modulated signals to interfere with a polarized local oscillator signal of predetermined frequency so as to generate two respective intermediate frequency signals, both having frequencies which fall within an intermediate frequency band of said detecting means.
Claim 18
Dependent Claim
29 words
A system as in claim 15 wherein said frequency modulated electromagnetic signal is caused to be incident on said birefringent medium at π/4 to the axis of said medium.
Claim 19
Dependent Claim
89 words
A system as claimed in claim 16 wherein said detecting means includes: a local source for generating said local signal; a main detector including electromagnetic to electrical signal conversion means and a filter having said intermediate frequency band; a coupler for coupling said transmitting means and said local source to said main detector; subsidiary detectors connected to said main detector which generate said digital data from said modulation signals, respectively; and processing means for generating said digital information in response to receiving said digital data from said subsidiary detectors.
Claim 20
Dependent Claim
32 words
A system as in claim 10, 11 or 12 wherein said modulating means is adapted to modulate the amplitude and/or phase of said frequency modulated electromagnetic signal in response to digital information.
Claim 21
Dependent Claim
20 words
A system in claim 18 wherein said transmitting means further includes an electromagnetic dielectric waveguide coupled to said birefringent medium.
Claim 22
Dependent Claim
21 words
A system as in claim 10, 11 or 12 wherein said frequency modulated electromagnetic and polarization modulated signals are optical signals.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-06-10 | 1994-12-10 | 1995-06-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-06-10 | 1998-12-10 | 1999-06-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-06-10 | 2002-12-10 | 2003-06-11 | $7700.00 | Window Closed / Lapsed |