Patent US6181450B1 successfully refreshed from Google Patents.
US6181450B1
Expired / Lapsed
US
⏱️ 0.0 years remaining
System and method for free space optical communications
Assignee: Harris Corp
•
Filing: 1998-05-12
•
Granted: 2001-01-30
•
Expires: 2018-05-12
Abstract
Abstract A method and system of communicating in free space using an optical communication system, such as for intersatellite and satellite-to-ground communications, is disclosed. Digital communication signals are multiplexed with a plurality of other analog communication signals into a single broad band frequency division multiplexed signal. A laser generates an optical carrier and an electro-optic modulator modulates the optical carrier signal with the frequency division multiplexed signal to produce a phase modulated optical communications signal. A receiver is positioned, such as in a satellite, to receive the phase modulated optical communications signal. The receiver includes a demodulator for demodulating the phase modulated optical communication system back into the broad band frequency division multiplexed signal and a demultiplexer for demultiplexing the broad band frequency division multiplexed signal into the plurality of communication signals. The portion of those signals that were previously digital data can be demodulated back into the digital communication signals.
Inventors
- 👤 John F. Dishman
- 👤 Edward R. Beadle
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 15:37
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/11; H04B10/118; H04B7/00; H04B7/14; H04B7/15; H04B7/185; H04B7/18521; G; G02; G02F; G02F1/00; G02F1/29; G02F1/291; G02F1/292; H04B7/1851; H04B7/18513
Claims Analysis
Total Claims: 36
Claim 1
Independent Claim
106 words
A method of communicating in free space comprising the steps of: frequency division multiplexing a plurality of communication signals into a single broad band frequency division multiplexed signal; phase modulating an optical carrier signal with the broad band frequency division multiplexed signal by mixing the multiplexed signal with the optical carrier signal in an electro-optic modulator to produce a phase modulated optical communications signal; transmitting the phase modulated optical communications signal to a receiver; demodulating the phase modulated optical communications signal back into the broad band frequency division multiplexed signal; and demultiplexing the broad band frequency division multiplexed signal into the plurality of analog communication signals.
Claim 2
Independent Claim
106 words
A method of communicating in free space comprising the steps of: frequency division multiplexing a plurality of communication signals into a single broad band frequency division multiplexed signal; phase modulating an optical carrier signal with the broad band frequency division multiplexed signal by mixing the multiplexed signal with the optical carrier signal in an electro-optic modulator to produce a phase modulated optical communications signal; transmitting the phase modulated optical communications signal to a receiver; demodulating the phase modulated optical communications signal back into the broad band frequency division multiplexed signal; and demultiplexing the broad band frequency division multiplexed signal into the plurality of analog communication signals.
Claim 3
Dependent Claim
35 words
A method according to claim 1 , and further comprising the steps of generating a plurality of digital communication signals and modulating the digital communication signals into digital waveform communication signals before frequency division multiplexing.
Claim 4
Dependent Claim
38 words
A method according to claim 1 , and further comprising the step of phase modulating the optical carrier signal by mixing the optical carrier signal and the broad band frequency division multiplexed signal within a Mach-Zender electro-optic modulator.
Claim 5
Dependent Claim
39 words
A method according to claim 1 , and further comprising the steps of up converting each of the plurality of analog communication signals into a defined frequency slot, and combining the frequencies to create the frequency division multiplexed signal.
Claim 6
Dependent Claim
34 words
A method according to claim 1 , and further comprising the step of non-mechanically steering the phase modulated optical communications signal by passing the communications signal through a Bragg cell and liquid crystal display.
Claim 7
Dependent Claim
32 words
A method according to claim 1 , and further comprising the step of beam spoiling the phase modulated optical communications signal by increasing the beam convergence of the communications signal during transmission.
Claim 8
Dependent Claim
25 words
A method according to claim 1 , and further comprising the step of demodulating the phase modulated optical communications signal by phase locked loop detection.
Claim 9
Independent Claim
146 words
A method of communicating in free space comprising the steps of: frequency division multiplexing a plurality of communication signals into a single broad band frequency division multiplexed signal; generating with a laser an optical carrier signal; phase modulating the optical carrier signal with the broad band frequency division multiplexed signal by mixing the multiplexed signal with the optical carrier signal in an electro-optic modulator; transmitting the phase modulated optical communications signal to a receiver while non-mechanically steering the optical communications signal by passing the optical communications signal through a Bragg cell and liquid crystal display to provide for fine indexing of the signal in the liquid crystal display and coarse two-dimensional indexing in the Bragg cell; demodulating the phase modulated optical communications signal back into the broad band frequency division multiplexed signal; and demultiplexing the frequency division multiplexed signal into the plurality of analog communication signals.
Claim 10
Independent Claim
146 words
A method of communicating in free space comprising the steps of: frequency division multiplexing a plurality of communication signals into a single broad band frequency division multiplexed signal; generating with a laser an optical carrier signal; phase modulating the optical carrier signal with the broad band frequency division multiplexed signal by mixing the multiplexed signal with the optical carrier signal in an electro-optic modulator; transmitting the phase modulated optical communications signal to a receiver while non-mechanically steering the optical communications signal by passing the optical communications signal through a Bragg cell and liquid crystal display to provide for fine indexing of the signal in the liquid crystal display and coarse two-dimensional indexing in the Bragg cell; demodulating the phase modulated optical communications signal back into the broad band frequency division multiplexed signal; and demultiplexing the frequency division multiplexed signal into the plurality of analog communication signals.
Claim 11
Dependent Claim
30 words
A method according to claim 8 , and further comprising the steps of applying a radio frequency signal to the Bragg cell to change the index of refraction for steering.
Claim 12
Dependent Claim
32 words
A method according to claim 8 , and further comprising the steps of passing the generated optical communications signal through first and second Bragg cell members for providing two dimensional, coarse steering.
Claim 13
Dependent Claim
30 words
A method according to claim 8 , and further comprising the steps of generating a plurality of communication signals and modulating the digital communication signals into digital waveform communication signals.
Claim 14
Dependent Claim
38 words
A method according to claim 8 , and further comprising the steps of phase modulating the optical carrier signal by mixing the optical carrier signal and the broad band frequency division multiplexed signal within a Mach-Zender electro-optic modulator.
Claim 15
Dependent Claim
40 words
A method according to claim 8 , and further comprising the steps of up converting each of the plurality of communication signals into a defined frequency slot, and combining the frequencies to create the broad band frequency division multiplexed signal.
Claim 16
Dependent Claim
35 words
A method according to claim 8 , and further comprising the step of non-mechanically steering the phase modulated optical communications signal by passing the optical carrier signal through a Bragg cell and liquid crystal display.
Claim 17
Dependent Claim
32 words
A method according to claim 8 , and further comprising the step of beam spoiling the phase modulated optical communications signal by increasing the beam convergence of the communications signal during transmission.
Claim 18
Dependent Claim
23 words
A method according to claim 8 , and further comprising the step of demodulating the phase modulated optical communications signal by heterodyne detection.
Claim 19
Independent Claim
118 words
A system for communicating in free space comprising: means for multiplexing a plurality of analog communication signals into a single frequency division multiplexed signal; a laser for generating an optical carrier signal; an electro-optic modulator that receives said frequency division multiplexed signal and said laser generated optical carrier signal and phase modulates the optical carrier signal with the multiplexed signal to produce a phase modulated optical communications signal; a receiver that receives the phase modulated optical communications signal, said receiver further comprising: a demodulator for demodulating the phase modulated optical communications signal back into the frequency division multiplexed signal, and a demultiplexer for demultiplexing the broad band frequency division multiplexed signal into the plurality of analog communication signals.
Claim 20
Independent Claim
118 words
A system for communicating in free space comprising: means for multiplexing a plurality of analog communication signals into a single frequency division multiplexed signal; a laser for generating an optical carrier signal; an electro-optic modulator that receives said frequency division multiplexed signal and said laser generated optical carrier signal and phase modulates the optical carrier signal with the multiplexed signal to produce a phase modulated optical communications signal; a receiver that receives the phase modulated optical communications signal, said receiver further comprising: a demodulator for demodulating the phase modulated optical communications signal back into the frequency division multiplexed signal, and a demultiplexer for demultiplexing the broad band frequency division multiplexed signal into the plurality of analog communication signals.
Claim 21
Dependent Claim
31 words
A system according to claim 17 , and further comprising means for generating a plurality of communication signals and means for modulating the digital communication signals into digital waveform communication signals.
Claim 22
Dependent Claim
18 words
A system according to claim 17 , and wherein said electro-optic modulator further comprises a Mach-Zender electro-optic modulator.
Claim 23
Dependent Claim
43 words
A system according to claim 17 , wherein said means for multiplexing further comprises a respective mixer for up converting respective analog signals into a defined frequency channel, and a combiner for combining the up converted frequencies into the frequency division multiplexed signal.
Claim 24
Dependent Claim
34 words
A system according to claim 17 , and further comprising a Bragg cell and liquid crystal display that receives the phase modulated optical communications signal for non-mechanically steering the phase modulated optical communications signal.
Claim 25
Dependent Claim
35 words
A system according to claim 17 , and further comprising a beam spoiler that receives the phase modulated optical communications signal for increasing the beam convergence of the phase modulated optical communications signal during transmission.
Claim 26
Dependent Claim
23 words
A system according to claim 17 , and further comprising a phase lock loop detector for demodulating the phase modulated optical communications signal.
Claim 27
Independent Claim
166 words
A system for communicating in free space comprising: means for multiplexing a plurality of analog communication signals into a single broad band frequency division multiplexed signal; a laser for generating an optical carrier signal; an electro-optic modulator that receives said broad band frequency division multiplexed signal and said laser generated optical carrier signal and phase modulates the optical carrier signal with the multiplexed signal to produce a phase modulated optical communications signal; steering means for non-mechanically steering the optical communications signal, said steering means further comprising: a Bragg cell to provide coarse two-dimensional indexing within the Bragg cell and a liquid crystal display to provide fine indexing of the phase modulated optical communications signal; a receiver that receives the phase modulated optical communications signal, said receiver further comprising: a demodulator for demodulating the phase modulated optical communications signal back into the broad band frequency division multiplexed signal, and a demultiplexer for demultiplexing the broad band frequency division multiplexed signal into the plurality of analog communication signals.
Claim 28
Independent Claim
166 words
A system for communicating in free space comprising: means for multiplexing a plurality of analog communication signals into a single broad band frequency division multiplexed signal; a laser for generating an optical carrier signal; an electro-optic modulator that receives said broad band frequency division multiplexed signal and said laser generated optical carrier signal and phase modulates the optical carrier signal with the multiplexed signal to produce a phase modulated optical communications signal; steering means for non-mechanically steering the optical communications signal, said steering means further comprising: a Bragg cell to provide coarse two-dimensional indexing within the Bragg cell and a liquid crystal display to provide fine indexing of the phase modulated optical communications signal; a receiver that receives the phase modulated optical communications signal, said receiver further comprising: a demodulator for demodulating the phase modulated optical communications signal back into the broad band frequency division multiplexed signal, and a demultiplexer for demultiplexing the broad band frequency division multiplexed signal into the plurality of analog communication signals.
Claim 29
Dependent Claim
30 words
A system according to claim 24 , and further comprising means for applying a radio frequency signal to the Bragg cell to change the index of refraction and provide steering.
Claim 30
Dependent Claim
25 words
A system according to claim 24 , wherein said Bragg cell further comprises first and second Bragg cell members to provide two dimensional, coarse steering.
Claim 31
Dependent Claim
30 words
A system according to claim 24 , and further comprising means for generating a plurality of communication signals and means for modulating the digital communication signals into analog communication signals.
Claim 32
Dependent Claim
18 words
A system according to claim 24 , and wherein said electro-optic modulator further comprises a Mach-Zender electro-optic modulator.
Claim 33
Dependent Claim
43 words
A system according to claim 24 , wherein said means for multiplexing further comprises a respective mixer for up converting respective analog signals into a defined frequency channel, and a combiner for combining the up converted frequencies into the frequency division multiplexed signal.
Claim 34
Dependent Claim
34 words
A system according to claim 24 , and further comprising a Bragg cell and liquid crystal display that receives the phase modulated optical communications signal for non-mechanically steering the phase modulated optical communications signal.
Claim 35
Dependent Claim
35 words
A system according to claim 24 , and further comprising a beam spoiler that receives the phase modulated optical communications signal for increasing the beam divergence of the phase modulated optical communications signal during transmission.
Claim 36
Dependent Claim
23 words
A system according to claim 24 , and further comprising a phase locked loop detector for demodulating the phase modulated optical communications signal.
References Cited (Backward Citations)
US3493759A
Cited
US3689841A
Cited
US4074234A
Cited
US4090036A
Cited
US4628493A
Cited
US4575186A
Cited
US4579421A
Cited
US4639092A
Cited
US4671620A
Cited
US4768186A
Cited
US4867560A
Cited
US4982445A
Cited
US5682256A
Cited
US4960322A
Cited
US5896211A
Cited
US5610748A
Cited
US5436751A
Cited
US5410421A
Cited
US5463493A
Cited
US5351148A
Cited
US5450223A
Cited
US5689354A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2004-01-30 | 2004-07-31 | 2005-01-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2008-01-30 | 2008-07-31 | 2009-01-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2012-01-30 | 2012-07-31 | 2013-01-30 | $7700.00 | Window Closed / Lapsed |