Patent US3909110A successfully refreshed from Google Patents.
US3909110A
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Reduction of dispersion in a multimode fiber waveguide with core index fluctuations
Assignee: AT&T Inc
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Filing: 1974-11-11
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Granted: 1975-09-30
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Expires: 1994-11-11
Abstract
Abstract Step index, multimode fiber waveguides are designed according to the disclosed invention with intentional fluctuations of the refractive index of the fiber core, with the aim of reducing dispersion by deliberately enhancing mode coupling in the fiber and, at the same time, minimizing loss in the fiber due to coupling to radiation modes. It is shown that, to avoid radiation losses, conditions should be imposed not only on the axial (z) dependence of the core fluctuations, but also on the azimuthal ( phi ) and radial (r) dependence of the core fluctuations. Specifically, a selection rule is imposed on the coupling in the fiber by providing the core index fluctuations with an azimuthal dependence governed by a function of the form cos p phi , where p is an integer equal to or greater than one. Coupling for a mode of an azimuthal mode number Nu is thereby limited by the selection rule Delta Nu p. Additionally, by limiting the location of the index fluctuations to a region below a certain maximum radius rmax in the core, coupling to modes with large azimuthal mode numbers Nu is avoided, and power loss via coupling to radiation modes is held to a minimum.
Inventors
- 👤 Dietrich Marcuse
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 19:48
CPC Classifications
G; G02; G02B; G02B6/00; G02B6/02; G02B6/02057; G02B6/10; G02B6/14
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
142 words
An optical fiber waveguide capable of guiding optical wave energy in a plurality of different modes of wave propagation having different group velocities and of dissipating wave energy in the form of radiation modes, said fiber including an inner core of radius a and of an unperturbed refractive index n1 surrounded by an outer cladding of refractive index n2 less then n1, said fiber further including means for minimizing dispersion due to said difference in group velocities comprising means for enhancing coupling among said guided modes in said fiber while minimizing coupling among said guided modes and said radiation modes, said fiber being characterized in that said means comprises spatial fluctuations in the refractive index of said inner core, said core index fluctuating in value periodically along the longitudinal axis of said fiber and in an azimuthal direction about said longitudinal axis.
Claim 2
Dependent Claim
142 words
An optical fiber waveguide capable of guiding optical wave energy in a plurality of different modes of wave propagation having different group velocities and of dissipating wave energy in the form of radiation modes, said fiber including an inner core of radius a and of an unperturbed refractive index n1 surrounded by an outer cladding of refractive index n2 less then n1, said fiber further including means for minimizing dispersion due to said difference in group velocities comprising means for enhancing coupling among said guided modes in said fiber while minimizing coupling among said guided modes and said radiation modes, said fiber being characterized in that said means comprises spatial fluctuations in the refractive index of said inner core, said core index fluctuating in value periodically along the longitudinal axis of said fiber and in an azimuthal direction about said longitudinal axis.
Claim 3
Dependent Claim
30 words
The optical fiber waveguide of claim 1 in which said core index fluctuations are limited to a region of said inner core below a maximum radius rmax less than a.
Claim 4
Dependent Claim
89 words
The optical fiber waveguide of claim 1 in which said core indes fluctuations have an azimuthal dependence of the form cos p phi where phi specifies the azimuthal position in said fiber and p is an integer equal to or greater than one, whereby the coupling in said fiber for a guided mode with an aximuthal mode number Nu is limited by the selection rule Delta Nu + or - p where Delta Nu is the difference in azimuthal mode number between any two guided modes that are coupled.
Claim 5
Dependent Claim
13 words
The optical fiber waveguide of claim 2 in which rmax is given by
Claim 6
Dependent Claim
234 words
An optical fiber waveguide capable of guiding optical wave energy in a plurality of different modes of wave propagation having different group velocities and of dissipating wave energy in the form of radiation modes, said fiber including an inner core of radius a and of an unperturbed refractive index n1 surrounded by an outer cladding of refractive index n2 less than n1, said fiber further including means for minimizing disperson due to said difference in group velocities comprising means for enhancing coupling among said guided modes in said fiber while minimizing coupling among said guided modes and said radiation modes, said fiber being characterized in that said means comprises spatial fluctuations in the refractive index n of said inner core given by n-n1 Delta nf(z) p( phi )g(r) where Delta n is the maximum difference in index (n-n1) between any two points along the longitudinal axis of said core, f(z) defines the axial dependence of said index fluctuations and is given by the superposition of sine waves whose spatial periods are equal to or greater than a minimum spatial period Lambda min, p( phi ) defines the azimuthal dependence of said index fluctuations and is given by cos p phi where phi specifies the azimuthal position in said core and p is an integer equal to or greater than one, and g(r) defines the radial dependence of said index fluctuation and is given by
Claim 7
Dependent Claim
234 words
An optical fiber waveguide capable of guiding optical wave energy in a plurality of different modes of wave propagation having different group velocities and of dissipating wave energy in the form of radiation modes, said fiber including an inner core of radius a and of an unperturbed refractive index n1 surrounded by an outer cladding of refractive index n2 less than n1, said fiber further including means for minimizing disperson due to said difference in group velocities comprising means for enhancing coupling among said guided modes in said fiber while minimizing coupling among said guided modes and said radiation modes, said fiber being characterized in that said means comprises spatial fluctuations in the refractive index n of said inner core given by n-n1 Delta nf(z) p( phi )g(r) where Delta n is the maximum difference in index (n-n1) between any two points along the longitudinal axis of said core, f(z) defines the axial dependence of said index fluctuations and is given by the superposition of sine waves whose spatial periods are equal to or greater than a minimum spatial period Lambda min, p( phi ) defines the azimuthal dependence of said index fluctuations and is given by cos p phi where phi specifies the azimuthal position in said core and p is an integer equal to or greater than one, and g(r) defines the radial dependence of said index fluctuation and is given by
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-29 | 1979-03-31 | 1979-09-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-29 | 1983-03-31 | 1983-09-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-29 | 1987-03-31 | 1987-09-30 | $7700.00 | Window Closed / Lapsed |