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US5617239A
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Optical source for communications system
Assignee: British Telecommunications PLC
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Filing: 1993-06-29
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Granted: 1997-04-01
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Expires: 2013-06-29
Abstract
Abstract PCT No. PCT/GB93/01353 Sec. 371 Date Jan. 17, 1995 Sec. 102(e) Date Jan. 17, 1995 PCT Filed Jun. 29, 1993 PCT Pub. No. WO94/00928 PCT Pub. Date Jan. 6, 1994An optical source for a communications system includes an optical signal source whose output is modulated to contain sidebands. The sidebands interact to produce beat frequencies and modifying apparatus, such as a length of dispersive optical fibre, is used to modify characteristics of the sidebands so that the beat frequency can be detected at a receiver such as a photodetector. In this way, high frequency signals can be generated and photodetected, the output of the receiver being suitable to drive a microwave antenna, thus providing an optically fed microwave communications link. Using a video signal generator a video signal can be superimposed on the received beat frequency and therefore carried by the microwave link.
Inventors
- 👤 Nigel G. Walker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 08:29
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/25; H04B10/2575; H04B10/25751; H04B2210/00; H04B2210/006
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
92 words
An optical communications system comprising: an optical signal source, said source having an optical output, modulation means to produce angle modulation in said optical output at a modulation frequency causing optical sidebands to appear in the optical output, modifying means to modify a relative characteristic of the optical sidebands in the optical output and allow photodetection of at least one harmonic of said modulation frequency at a receiver receiving said optical output, and a receiver for receiving and photodetecting said optical output to produce at least one harmonic of said modulation frequency.
Claim 2
Dependent Claim
92 words
An optical communications system comprising: an optical signal source, said source having an optical output, modulation means to produce angle modulation in said optical output at a modulation frequency causing optical sidebands to appear in the optical output, modifying means to modify a relative characteristic of the optical sidebands in the optical output and allow photodetection of at least one harmonic of said modulation frequency at a receiver receiving said optical output, and a receiver for receiving and photodetecting said optical output to produce at least one harmonic of said modulation frequency.
Claim 3
Dependent Claim
17 words
A system as in claim 1, wherein said modulation means produces phase modulation in said optical output.
Claim 4
Dependent Claim
16 words
A system as in claim 1, wherein said modulation means produces frequency modulation in said output.
Claim 5
Dependent Claim
13 words
A system as in claim 1, wherein said relative characteristic is relative phase.
Claim 6
Dependent Claim
15 words
A system as in claim 4, wherein said phase modifying means comprises a dispersive element.
Claim 7
Dependent Claim
31 words
A system as in claim 1, further comprising a microwave antenna which in use receives the said at least one harmonic of said modulation frequency subsequent to photodetection by the receiver.
Claim 8
Dependent Claim
77 words
An optical signal source for use in a communications system, said source having: an optical output, modulation means to produce angle modulation in said optical output to cause optical sidebands to appear in the optical output, and modifying means comprises a length of optical fibre to modify the relative phases of the optical sidebands in the optical output to allow photodetection of at least one beat frequency between said sidebands at a receiver receiving said optical output.
Claim 9
Dependent Claim
77 words
An optical signal source for use in a communications system, said source having: an optical output, modulation means to produce angle modulation in said optical output to cause optical sidebands to appear in the optical output, and modifying means comprises a length of optical fibre to modify the relative phases of the optical sidebands in the optical output to allow photodetection of at least one beat frequency between said sidebands at a receiver receiving said optical output.
Claim 10
Dependent Claim
13 words
A source as in claim 7, the source comprising a semiconductor laser structure.
Claim 11
Dependent Claim
18 words
A source as in claim 8, wherein said laser structure comprises a laser suitable for direct frequency modulation.
Claim 12
Dependent Claim
23 words
A source as in claim 8, wherein said laser structure comprises a continuous wave laser and said modulation means comprises a phase modulator.
Claim 13
Independent Claim
77 words
A method of generating a radio frequency signal comprising: (i) driving a semiconductor optical source at a drive current sufficient to generate an optical output; (ii) angle modulating said optical output at a modulation frequency to generate optical sidebands in the optical output; (iii) modifying a relative characteristic of said optical sidebands in the optical output; and (iv) photodetecting said optical output to produce an electrical signal which comprises at least one harmonic of said modulation frequency.
Claim 14
Independent Claim
77 words
A method of generating a radio frequency signal comprising: (i) driving a semiconductor optical source at a drive current sufficient to generate an optical output; (ii) angle modulating said optical output at a modulation frequency to generate optical sidebands in the optical output; (iii) modifying a relative characteristic of said optical sidebands in the optical output; and (iv) photodetecting said optical output to produce an electrical signal which comprises at least one harmonic of said modulation frequency.
Claim 15
Dependent Claim
13 words
A method as in claim 11, wherein said relative characteristic in relative phase.
Claim 16
Dependent Claim
41 words
A method of generating a free space microwave communications signal comprising the steps i) to iv) according to claim 11, and further step of: v) feeding a harmonic of said modulation frequency included in said electrical signal to a microwave antenna.
Claim 17
Dependent Claim
16 words
A system as in claim 5, wherein the dispersive element comprises a length of optical fibre.
Claim 18
Dependent Claim
21 words
A method as in claim 12, wherein step (iii) comprises conducting said optical output through a length of dispersive optical fibre.
Claim 19
Dependent Claim
15 words
A system as in claim 1, wherein said modulation frequency is a modulated carrier frequency.
Claim 20
Dependent Claim
15 words
A method as in claim 11, wherein said modulation frequency is a modulated carrier frequency.
Claim 21
Independent Claim
92 words
A method of generating a radio frequency signal comprising: (i) driving a semiconductor optical source at a drive current sufficient to generate an optical output; (ii) angle modulating said optical output to generate optical sidebands in the optical output; (iii) conducting the optical output through a length of dispersive optical fibre to modify the relative phases of the optical sidebands in the optical output; and (iv) photodetecting said optical output after its conduction through the optical fibre to produce an electrical signal which comprises at least one beat frequency between said sidebands.
Claim 22
Independent Claim
92 words
A method of generating a radio frequency signal comprising: (i) driving a semiconductor optical source at a drive current sufficient to generate an optical output; (ii) angle modulating said optical output to generate optical sidebands in the optical output; (iii) conducting the optical output through a length of dispersive optical fibre to modify the relative phases of the optical sidebands in the optical output; and (iv) photodetecting said optical output after its conduction through the optical fibre to produce an electrical signal which comprises at least one beat frequency between said sidebands.
Claim 23
Dependent Claim
40 words
A method of generating a free space microwave communications signal comprising the steps (i) to (iv) according to claim 18 and the further step of (v) feeding a said beat frequency included in said electrical signal to a microwave antenna.
Claim 24
Independent Claim
112 words
A method of generating a radio frequency signal above 20 GHz for use in a wideband communications system, said method comprising the steps of: (i) angle modulating a coherent optical signal to generate optical sidebands thereto; (ii) passing said modulated optical signal through an optically dispersive optical signal processing component to modify the relative phases of optical signals in said optical sidebands; (iii) photodetecting the optically dispersed optical signal output of step (ii) to produce an electrical signal including multiple harmonic frequency components and heterodyned beat frequency components therebetween; and (iv) selectively passing at least one of said electrical beat frequency signals for use as said radio frequency signal above 20 GHz.
Claim 25
Independent Claim
112 words
A method of generating a radio frequency signal above 20 GHz for use in a wideband communications system, said method comprising the steps of: (i) angle modulating a coherent optical signal to generate optical sidebands thereto; (ii) passing said modulated optical signal through an optically dispersive optical signal processing component to modify the relative phases of optical signals in said optical sidebands; (iii) photodetecting the optically dispersed optical signal output of step (ii) to produce an electrical signal including multiple harmonic frequency components and heterodyned beat frequency components therebetween; and (iv) selectively passing at least one of said electrical beat frequency signals for use as said radio frequency signal above 20 GHz.
References Cited (Backward Citations)
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