US4839614A — Frequency referencing system and method

Claim 1

Independent Claim 86 words

A method of referencing the frequencies of radiation from a plurality of sources, the method comprising: guiding the radiation from each source to a filter element having a replicated set of passbands spaced apart in frequency; monitoring radiation at each of the wavelengths transmitted through the filter element; and controlling the sources so that the radiation at each wavelength transmitted through the filter element is maintained substantially constant, the bandwidths of the radiation at each wavelength being smaller than the corresponding passbands of the filter element.

Claim 2

Independent Claim 86 words

A method of referencing the frequencies of radiation from a plurality of sources, the method comprising: guiding the radiation from each source to a filter element having a replicated set of passbands spaced apart in frequency; monitoring radiation at each of the wavelengths transmitted through the filter element; and controlling the sources so that the radiation at each wavelength transmitted through the filter element is maintained substantially constant, the bandwidths of the radiation at each wavelength being smaller than the corresponding passbands of the filter element.

Claim 3

Dependent Claim 34 words

A method according to claim 1, wherein the intensity of the transmitted radiation is monitored, the bandwidths of the radiation being offset from the central frequency of the corresponding passbands of the filter element.

Claim 4

Dependent Claim 36 words

A method according to claim 1, wherein either the radiation frequency is modulated or the frequency spacing of the passbands of the filter element is modulated, the amplitude and phase of the detected sub-carrier being monitored.

Claim 5

Independent Claim 50 words

A method according to anyone of claims 1 to 3, wherein one source comprises a reference source for generating a reference beam, the method further comprising monitoring transmitted radiation corresponding to the reference beam, and adjusting the filter element to maintain the transmission characteristic of the reference beam substantially constant.

Claim 6

Independent Claim 57 words

A method according to anyone of the preceding claims, 1, 2 or 3 further comprising imparting respective identifiers to the radiation from each source; guiding the radiation from each source along a common path to the filter element; detecting from the radiation transmitted through the filter element each identifier; and detecting the radiation corresponding to the identifiers.

Claim 7

Dependent Claim 16 words

A method according to claim 5, wherein the identifier comprises a frequency or time code modulation.

Claim 8

Independent Claim 19 words

A method according to anyone of the preceding claims 1, 2 or 3 wherein the radiation is optical radiation.

Claim 9

Dependent Claim 113 words

A frequency referencing system comprising: a plurality of sources of radiation of different frequencies; a filter element having a replicated set of passbands spaced apart in frequency on to which the radiation from each source is incident; detection means for detecting the intensity of the radiation at each wavelength passing through the filter element and for providing output signals corresponding to each wavelength; and control means responsive to the output signals from the detection means to control the sources so that the radiation at each wavelength transmitted through the filter element is maintained substantially constant, the bandwidths of the radiation at each wavelength being smaller than the corresponding passbands of the filter element.

Claim 10

Dependent Claim 113 words

A frequency referencing system comprising: a plurality of sources of radiation of different frequencies; a filter element having a replicated set of passbands spaced apart in frequency on to which the radiation from each source is incident; detection means for detecting the intensity of the radiation at each wavelength passing through the filter element and for providing output signals corresponding to each wavelength; and control means responsive to the output signals from the detection means to control the sources so that the radiation at each wavelength transmitted through the filter element is maintained substantially constant, the bandwidths of the radiation at each wavelength being smaller than the corresponding passbands of the filter element.

Claim 11

Dependent Claim 39 words

A system according to claim 8, wherein one source comprises a reference source the system further including means for adjusting the filter element in response to output signals from the detection means corresponding to radiation from the reference source.

Claim 12

Dependent Claim 23 words

A system according to claim 8 or claim 9, wherein the passbands of the filter element are substantially equally spaced apart in frequency.

Claim 13

Independent Claim 23 words

A system according to any one of claims 8 or 9, wherein the filter element comprises a Fabry-Perot etalon or a ring resonator.

Claim 14

Independent Claim 77 words

A system according to anyone of claims 8 or 9, wherein radiation from the plurality of sources is guided along the same path to the filter element, common detection. means being provided to receive the radiation transmitted through the filter element, and the control means being arranged to impart respective identifiers to the radiation from each source and to detect from the radiation passing through the filter element each identifier and the radiation corresponding to the identifier.

Claim 15

Independent Claim 15 words

A system according to anyone of claims 8 or 9, wherein the sources comprise lasers.

Claim 16

Dependent Claim 101 words

A communications network comprising a frequency referencing system according to anyone of claims 8 or to 9 in which each source of radiation comprises a reference source, multiplexing means for multiplexing the frequency referenced radiation from the reference sources and splitting means for splitting the multiplexed radiation into a plurality of subsidiary signals each of which is fed to a respective set of remote sources of radiation; and subsidiary control means at each set of subsidiary sources for referencing the frequencies of the radiation from the subsidiary sources to one or more of the reference frequencies supplied from the splitting means.

Claim 17

Independent Claim 140 words

A method for simultaneously controlling the operating optical frequencies of plural lasers, said method comprising the steps of: passing the optical radiation output from each of said plural lasers through a single common optical frequency filter having a plurality of passbands spaced apart in the optical frequency domain, the output of each laser being controllable in frequency to align with a respective one of said passbands in the frequency domain; processing the optical radiation passed through said filter to derive a plurality of frequency control electrical signals, each of said control electrical signals corresponding to the radiation passed through a respectively corresponding passband of the filter by a respectively corresponding laser; and using said plural frequency control electrical signals to actively control the operating optical frequency of its respective laser and maintain such operating frequency within its associated filter passband.

Claim 18

Independent Claim 140 words

A method for simultaneously controlling the operating optical frequencies of plural lasers, said method comprising the steps of: passing the optical radiation output from each of said plural lasers through a single common optical frequency filter having a plurality of passbands spaced apart in the optical frequency domain, the output of each laser being controllable in frequency to align with a respective one of said passbands in the frequency domain; processing the optical radiation passed through said filter to derive a plurality of frequency control electrical signals, each of said control electrical signals corresponding to the radiation passed through a respectively corresponding passband of the filter by a respectively corresponding laser; and using said plural frequency control electrical signals to actively control the operating optical frequency of its respective laser and maintain such operating frequency within its associated filter passband.

Claim 19

Dependent Claim 54 words

A method as in claim 15 further comprising the step of also passing reference optical radiation from a reference laser of predetermined stable operating frequency through said single common optical frequency filter; and using optical radiation from the reference source passed by the filter to actively control the frequency of the plural filter passbands.

Claim 20

Independent Claim 110 words

A system for simultaneously controlling the operating optical frequencies of plural lasers, said system comprising: plural controllable frequency laser sources of optical radiation; a common optical frequency filter disposed to intercept radiation emanating from each of said laser sources, said filter having a plurality of passbands spaced apart in the optical frequency domain; feedback control circuits for converting radiation passed by said filter into a plurality of electrical control signals, each being representative of the alignment of a respectively associated filter passband and laser output frequency and for applying said electrical signals to control the respective laser output frequencies and thus maintain each with an associated passband of the filter.

Claim 21

Independent Claim 110 words

A system for simultaneously controlling the operating optical frequencies of plural lasers, said system comprising: plural controllable frequency laser sources of optical radiation; a common optical frequency filter disposed to intercept radiation emanating from each of said laser sources, said filter having a plurality of passbands spaced apart in the optical frequency domain; feedback control circuits for converting radiation passed by said filter into a plurality of electrical control signals, each being representative of the alignment of a respectively associated filter passband and laser output frequency and for applying said electrical signals to control the respective laser output frequencies and thus maintain each with an associated passband of the filter.

Claim 22

Dependent Claim 71 words

A system as in claim 17 further comprising: a reference laser having a stable predetermined operating optical frequency and arranged to direct at least some of its optical output through said filter; and filter frequency control means connected and disposed to receive reference frequency radiation from the reference laser and passed by the filter and to control the filter to maintain one of its passbands aligned therewith in the frequency domain.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1992-06-12	1992-12-12	1993-06-13	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1996-06-12	1996-12-12	1997-06-13	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2000-06-12	2000-12-12	2001-06-13	$7700.00	Window Closed / Lapsed

Frequency referencing system and method

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