US4560246A
Expired / Lapsed
US
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Optical transmission
Assignee: British Telecommunications PLC
•
Filing: 1983-06-02
•
Granted: 1985-12-24
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Expires: 2003-06-02
Abstract
Abstract Stimulated Brillouin Scattering, which occurs when light of narrow linewidth and above a threshold power is launched into a low loss optical fiber, is suppressed by time-varying the phase angle of the transmitted light waves.
Inventors
- 👤 David Cotter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 19:30
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/25; H04B10/2507; H04B10/2537
Claims Analysis
Total Claims: 41
Claim 1
Independent Claim
90 words
A method of transmitting coherent light along an optical fibre in an optical communication system at power levels which exceed the normally expected Stimulated Brillouin Scattering (SBS) threshold which method comprises: launching into the fibre a coherent optical wave having a power level in excess of the normally expected Stimulated Brillouin Scattering threshold and a phase angle which is varied with respect to time in such a manner that Stimulated Brillouin Scattering is substantially suppressed and the power level of the successfully propagated component of the optical wave is increased.
Claim 2
Independent Claim
90 words
A method of transmitting coherent light along an optical fibre in an optical communication system at power levels which exceed the normally expected Stimulated Brillouin Scattering (SBS) threshold which method comprises: launching into the fibre a coherent optical wave having a power level in excess of the normally expected Stimulated Brillouin Scattering threshold and a phase angle which is varied with respect to time in such a manner that Stimulated Brillouin Scattering is substantially suppressed and the power level of the successfully propagated component of the optical wave is increased.
Claim 3
Independent Claim
99 words
A method of optically transmitting information along light conducting fibres having increased length between required repeater amplifying stations, which method comprises: launching into an optical fibre at least one coherent optical wave having a power level in excess of the normally expected Stimulated Brillouin Scattering threshold and having effected phase reversals which occur more frequenly than the spontaneous acoustic dephasing time Δν B -1 =πΓ -1 (where Γ -1 =the acoustic phonon lifetime) so as to substantially suppress stimulated Brillouin Scattering, and modulating at least one component of said optical wave in correspondence with the information to be transmitted.
Claim 4
Independent Claim
99 words
A method of optically transmitting information along light conducting fibres having increased length between required repeater amplifying stations, which method comprises: launching into an optical fibre at least one coherent optical wave having a power level in excess of the normally expected Stimulated Brillouin Scattering threshold and having effected phase reversals which occur more frequenly than the spontaneous acoustic dephasing time Δν B -1 =πΓ -1 (where Γ -1 =the acoustic phonon lifetime) so as to substantially suppress stimulated Brillouin Scattering, and modulating at least one component of said optical wave in correspondence with the information to be transmitted.
Claim 5
Dependent Claim
44 words
A method of optically transmitting information as in claim 2 wherein binary-valued digital information is binary phase-shift-keyed onto said optical wave in correspondence with the information to be transmitted, the magnitude of each keyed phase shift being (2n+1)π, n being zero or an integer.
Claim 6
Dependent Claim
42 words
A method of optically transmitting information as in claim 2 wherein binary-valued digital information is frequency-shift-keyed onto said optical wave in correspondence with said information, the magnitude of the keyed frequency shift being sufficiently great that Stimulated Brillouin Scattering is substantially suppressed.
Claim 7
Dependent Claim
16 words
A method according to claim 4, wherein the frequency shift keying is binary frequency shift keying.
Claim 8
Dependent Claim
21 words
A method according to claim 3, 4 or 5, wherein the bit rate is at least 100 MBit s -1 .
Claim 9
Dependent Claim
32 words
A method according to claim 2 wherein said launching step comprises producing and combining coherent optical waves of differing frequencies by the addition of which the variation of phase angle is achieved.
Claim 10
Dependent Claim
18 words
A method according to claim 7, wherein the waves of differing frequencies originate simultaneously in a single source.
Claim 11
Dependent Claim
22 words
A method according to claim 8 wherein said source is a laser and the waves are different longitudinal modes of the laser.
Claim 12
Dependent Claim
27 words
A method according to claim 8 or 9 wherein the modulation in correspondence with the information to be transmitted is effected by control of the said source.
Claim 13
Dependent Claim
24 words
A method according to claim 7, 8 or 9 wherein the modulation in accordance with the information to be transmitted is an amplitude modulation.
Claim 14
Independent Claim
88 words
A method of transmitting coherent light along an optical fibre, wherein the light linewidth determines a natural Stimulated Brillouin Scattering threshold power level for the fibre, the method comprising: generating coherent light having a predetermined linewidth in light generating means, introducing recurrent phase deviations in said coherent light, and launching said light into an optical fibre at a power level which is above the natural Stimulated Brillouin Scattering threshold power level for the fibre at said predetermined linewidth, wherein the recurrent phase deviations substantially suppress Stimulated Brillouin Scattering.
Claim 15
Independent Claim
88 words
A method of transmitting coherent light along an optical fibre, wherein the light linewidth determines a natural Stimulated Brillouin Scattering threshold power level for the fibre, the method comprising: generating coherent light having a predetermined linewidth in light generating means, introducing recurrent phase deviations in said coherent light, and launching said light into an optical fibre at a power level which is above the natural Stimulated Brillouin Scattering threshold power level for the fibre at said predetermined linewidth, wherein the recurrent phase deviations substantially suppress Stimulated Brillouin Scattering.
Claim 16
Dependent Claim
56 words
A method according to claim 12, wherein said generating, introducing and launching steps comprise: generating coherent light at a plurality of distinct wavelengths, and launching a composite light wave comprising said distinct plurality of wavelengths into said fibre, thereby to introduce said recurrent phase deviations as a result of superposition of light of said distinct wavelengths.
Claim 17
Dependent Claim
52 words
A method according to claim 13, further comprising: generating said coherent light at a plurality of distinct wavelengths in light generating means comprising a single laser source, and transmitting information by applying to the light of at least one of said distinct wavelengths a modulation in correspondence with information to be transmitted.
Claim 18
Dependent Claim
53 words
A method according to claim 13, further comprising: generating said coherent light at a plurality of distinct wavelengths in light generating means comprising a plurality of sources, and transmitting information by applying to the light of at least one of said distinct wavelengths a modulation in correspondence with the information to be transmitted.
Claim 19
Dependent Claim
14 words
A method according to claim 14 or 15 wherein the modulation is amplitude modulation.
Claim 20
Dependent Claim
27 words
A method according to claim 14 or 15, comprising generating the coherent light of each distinct wavelength from a separate longitudinal mode of a laser light source.
Claim 21
Dependent Claim
33 words
A method according to claim 12, further comprising: transmitting information by applying to the light a modulation in correspondence with the information to be transmitted, wherein said modulation introduces said recurrent phase deviations.
Claim 22
Dependent Claim
38 words
A method according to claim 18, wherein the information is binary-valued digital information, and the modulation is binary phase shift keying, the recurrent phase deviations being keyed phase shifts of substantially (2n+1)π, (n being zero or an integer).
Claim 23
Dependent Claim
30 words
A method according to claim 18, wherein the information is binary-valued digital information, and the modulation is frequency shift keying, the recurrent phase deviations being introduced by keyed frequency shifts.
Claim 24
Dependent Claim
16 words
A method according to claim 20, wherein the frequency shift keying is binary-valued frequency shift keying.
Claim 25
Dependent Claim
23 words
A method according to claim 19, 20 or 21 wherein the information is transmitted at a bit rate of at least 100 MBit/s.
Claim 26
Dependent Claim
66 words
A method according to claim 12 wherein said generating, introduced and launching steps comprise: generating coherent light at a plurality of distinct wavelengths, introducing said recurrent phase deviations into the light of at least one of said distinct wavelengths, and transmitting information by applying to the light of at least one other of said distinct wavelengths a modulation in correspondence with the information to be transmitted.
Claim 27
Dependent Claim
76 words
A method of transmitting and receiving information along an optical fibre comprising: transmitting information by launching coherent light of at least one wavelength into one end of an optical fibre, which launched light is modulated in correspondence with the information to be transmitted by a method according to claim 36, 37, 40 or 45, coherently detecting the transmitted light emerging from the other end of the fibre, and demodulating said detected light to recover said information.
Claim 28
Dependent Claim
30 words
A method according to claim 14, 15, 18 or 23 wherein the modulation in correspondence with the information to be transmitted is effected by control of the light generating means.
Claim 29
Dependent Claim
86 words
An optical transmission system comprising: an optical fibre having a natural stimulated Brillouin scattering power threshold for a given linewidth light, light generating means to generate light of predetermined linewidth and at a power above the natural Stimulated Brillouin Scattering power threshold for the fibre at that linewidth, means to launch said generated light into the fibre at said excess power level, and means for introducing recurrent phase deviations in the transmitted light at a rate which is sufficiently high to substantially suppress Stimulated Brillouin Scattering.
Claim 30
Dependent Claim
86 words
An optical transmission system comprising: an optical fibre having a natural stimulated Brillouin scattering power threshold for a given linewidth light, light generating means to generate light of predetermined linewidth and at a power above the natural Stimulated Brillouin Scattering power threshold for the fibre at that linewidth, means to launch said generated light into the fibre at said excess power level, and means for introducing recurrent phase deviations in the transmitted light at a rate which is sufficiently high to substantially suppress Stimulated Brillouin Scattering.
Claim 31
Dependent Claim
33 words
An optical transmission system according to claim 26, for transmitting information, wherein the means for introducing recurrent phase deviations comprises modulating means for modulating the light in correspondence with information to be transmitted.
Claim 32
Dependent Claim
37 words
An optical transmission system according to claim 27, for transmitting binary-valued digital information, wherein said modulating means includes binary phase shift keying means for effecting recurrent phase deviations of substantially (2n+1)π, (n being zero or an integer).
Claim 33
Dependent Claim
37 words
An optical transmission system according to claim 27, for transmitting binary-valued digital information, wherein said modulating means includes frequency shift keying means for effecting said recurrent phase deviations by introducing keyed frequency shifts in said transmitted light.
Claim 34
Dependent Claim
38 words
An optical transmission system according to claim 26, wherein said light generating means generates plural light waves at a corresponding plurality of distinct wavelengths and said recurrent phase deviations are introduced by superposition of said plural light waves.
Claim 35
Dependent Claim
28 words
An optical transmission system according to claim 30, wherein the light generating means comprises a single optical source to generate light waves at a plurality of distinct wavelengths.
Claim 36
Dependent Claim
19 words
An optical transmission system according to claim 30, wherein the light generating means comprises a plurality of optical sources.
Claim 37
Dependent Claim
23 words
An optical transmission system according to claim 31 or 32 wherein the distinct wavelengths are separate longitudinal modes of a laser light source.
Claim 38
Dependent Claim
41 words
An optical transmission system according to claim 30, for transmitting information, further comprising modulating means for applying to the light of at least one of said plurality of distinct wavelengths an amplitude modulation in correspondence with the information to be transmitted.
Claim 39
Dependent Claim
19 words
An optical transmission system according to claim 27 or 34 wherein the modulating means controls the light generating means.
Claim 40
Dependent Claim
29 words
An optical communication system comprising: a transmission system according to claim 26, 27 or 30 and further comprising means to coherently detect and receive light emerging from the fibre.
Claim 41
Dependent Claim
39 words
An optical system according to claims 26, 27 or 30 wherein said optical fibre is a silica fibre having a loss not exceeding 0.5 dB/km at the wavelength of operation, and having a length of at least 10 km.
References Cited (Backward Citations)
US4261640A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-12-23 | 1989-06-24 | 1989-12-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-12-23 | 1993-06-24 | 1993-12-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-12-23 | 1997-06-24 | 1997-12-24 | $7700.00 | Window Closed / Lapsed |