Patent US4955026A successfully refreshed from Google Patents.
US4955026A
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Frequency locking radiation beam
Assignee: British Telecommunications PLC
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Filing: 1987-11-12
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Granted: 1990-09-04
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Expires: 2007-11-12
Abstract
Abstract A method and apparatus for locking the frequencies of a number of first beams of coherent radiation from respective sources (17) are disclosed. Typically, the sources (17) will form local oscillators in respective transmitters (1). The apparatus comprises a reference beam generator (10) such as a HeNe laser which generates a primary reference beam fed to an interferometer (12) which generates a second, reference beam composed of a number of reference frequencies. This second reference beam is caused to interfere with each of the beams from the local sources (17) in an optical coupler (16) and the resultant beam is detected with a photodiode (22). The electrical output signal of the photodiode (22) is filtered and fed to a discriminator (25) which controls the frequency of the local laser (17). The discriminator (25) controls the laser (17) to maintain the relationship between the frequencies of the laser (17) and the reference laser (10) substantially constant.
Inventors
- 👤 Godfrey R. Hill
- 👤 David W. Smith
- 👤 David J. Hunkin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 21:13
CPC Classifications
H; H01; H01S; H01S5/00; H01S5/0014; G; G02; G02F; G02F2/00; H01S3/00; H01S3/10; H01S3/13; H01S3/139; H01S3/1394; G01; G01J; G01J9/00; G01J9/02; G01J9/0246; G01J9/04; H01S5/06; H01S5/068; H01S5/0683; H01S5/0687
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
143 words
A method of locking the frequencies of a plurality of first beams of coherent radiation at respective different and closely spaced frequencies, the method comprising: generating a first beam of coherent radiation from each of a plurality of first sources of coherent radiation to produce a plurality of first beams having associated first beam frequencies; generating a reference beam of coherent radiation composed of a plurality of reference frequencies, each reference frequency having a different value, and being spaced apart from each other reference frequency by a predetermined amount; monitoring the difference between each first beam frequency and a respective one of the reference frequencies; and modifying each of the first beam frequencies to maintain predetermined differences with respect to respective reference frequencies substantially constant, thereby locking each first beam at a frequency which differs from the frequency of each other first beam.
Claim 2
Independent Claim
143 words
A method of locking the frequencies of a plurality of first beams of coherent radiation at respective different and closely spaced frequencies, the method comprising: generating a first beam of coherent radiation from each of a plurality of first sources of coherent radiation to produce a plurality of first beams having associated first beam frequencies; generating a reference beam of coherent radiation composed of a plurality of reference frequencies, each reference frequency having a different value, and being spaced apart from each other reference frequency by a predetermined amount; monitoring the difference between each first beam frequency and a respective one of the reference frequencies; and modifying each of the first beam frequencies to maintain predetermined differences with respect to respective reference frequencies substantially constant, thereby locking each first beam at a frequency which differs from the frequency of each other first beam.
Claim 3
Dependent Claim
87 words
A method according to claim 1 wherein: the monitoring step comprises splitting the reference beam into a number of subsidiary reference beams, causing each first beam to interfere with a respective one of the subsidiary beams to generate respective intermediate beams composed of a number of intermediate frequencies each having a respective signal level, and, for each intermediate beam monitoring one of the intermediate frequencies, and the modifying step comprises modifying the first beam frequencies t maintain the signal level of the monitored intermediate frequencies substantially constant.
Claim 4
Dependent Claim
41 words
A method according to claim 2, wherein the second reference beam of coherent radiation is generated by modulating a primary reference beam of coherent radiation with a rf signal to provide intermediate beams whereby the number of reference frequencies are generated.
Claim 5
Dependent Claim
53 words
A method according to claim 3, wherein: the or each modulated reference beam is further modulated with a relatively low frequency whereby the frequencies of the intermediate beams are subject to different deviations depending upon the reference frequency involved; and the modifying step occurs provided the monitored intermediate frequencies include a desired deviation.
Claim 6
Independent Claim
23 words
A method according to any one of the preceding claims 1, 2, 3 or 4 wherein the beams of radiation comprise optical beams.
Claim 7
Dependent Claim
158 words
Apparatus for locking the frequencies of a plurality of first beams of coherent radiation at respective different and closely spaced frequencies, the apparatus comprising: a plurality of sources of coherent radiation for generating the plurality of first beams of coherent radiation each having a corresponding first beam frequency; a reference beam generator for generating a reference beam of coherent radiation composed of a plurality of reference frequencies, each reference frequency having a different value, and being spaced apart from each other reference frequency by a predetermined amount; monitoring means for monitoring the difference between the frequency of each first beam and a respective one of the reference frequencies and for generating corresponding control signals; and modifying means responsive to the control signals for modifying each first beam frequency to maintain predetermined differences with respect to respective reference frequencies substantially constant, thereby locking each first beam at a frequency which differs from the frequency of each other first beam.
Claim 8
Dependent Claim
158 words
Apparatus for locking the frequencies of a plurality of first beams of coherent radiation at respective different and closely spaced frequencies, the apparatus comprising: a plurality of sources of coherent radiation for generating the plurality of first beams of coherent radiation each having a corresponding first beam frequency; a reference beam generator for generating a reference beam of coherent radiation composed of a plurality of reference frequencies, each reference frequency having a different value, and being spaced apart from each other reference frequency by a predetermined amount; monitoring means for monitoring the difference between the frequency of each first beam and a respective one of the reference frequencies and for generating corresponding control signals; and modifying means responsive to the control signals for modifying each first beam frequency to maintain predetermined differences with respect to respective reference frequencies substantially constant, thereby locking each first beam at a frequency which differs from the frequency of each other first beam.
Claim 9
Dependent Claim
75 words
Apparatus according to claim 6, wherein the monitoring means comprises: a beam splitter for splitting the second reference beam into a number of subsidiary reference beams, coupling means for causing each first beam to interfere with a respective one of the subsidiary beams whereby respective intermediate beams composed of a number of intermediate frequencies are generated, and sensing means for monitoring respective ones of the intermediate frequencies in generating the control signals in response thereto.
Claim 10
Dependent Claim
40 words
Apparatus according to claim 6 or claim 7 wherein the reference beam generator comprises a primary reference beam source, a RF signal source, and a modulator to which the primary reference beam is fed for modulation by the RF signal.
Claim 11
Dependent Claim
13 words
Apparatus according to claim 8 wherein said modulator comprises an optical comb generator.
Claim 12
Dependent Claim
40 words
Apparatus according to claim 9 further comprising a number of first sources for generating the first radiation beams, the first sources responding to the control signals generated by the monitoring means to adjust the frequencies of the respective first beams.
Claim 13
Dependent Claim
45 words
Apparatus according to any one of claims 6 or 7, further comprising a number of first sources for generating the first radiation beams, the first sources responding to the control signals generated by the monitoring means to adjust the frequencies of the respective first beams.
Claim 14
Independent Claim
70 words
A method for simultaneously stabilizing and maintaining respectively different operating frequencies for plural laser sources of coherent radiation, said method comprising the steps of: generating a plurality of coherent optical reference signals collectively defining a comb of amplitude versus frequency reference signals having stably maintained frequency differences therebetween; and locking a frequency control circuit associated with each of said laser sources onto a respectively different one of said reference signals.
Claim 15
Independent Claim
70 words
A method for simultaneously stabilizing and maintaining respectively different operating frequencies for plural laser sources of coherent radiation, said method comprising the steps of: generating a plurality of coherent optical reference signals collectively defining a comb of amplitude versus frequency reference signals having stably maintained frequency differences therebetween; and locking a frequency control circuit associated with each of said laser sources onto a respectively different one of said reference signals.
Claim 16
Independent Claim
58 words
A system of plural laser sources of coherent radiation simultaneously stabilized to operate on respectively different operating frequencies, said system comprising: a comb source of plural optical reference signals having stabilized frequency differences therebetween; and a frequency control circuit associated with each of said lasers and adapted to lock onto a respectively different one of said reference signals.
Claim 17
Independent Claim
58 words
A system of plural laser sources of coherent radiation simultaneously stabilized to operate on respectively different operating frequencies, said system comprising: a comb source of plural optical reference signals having stabilized frequency differences therebetween; and a frequency control circuit associated with each of said lasers and adapted to lock onto a respectively different one of said reference signals.
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