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US4057320A
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Optical fiber waveguide having minimum modal dispersion
Assignee: AT&T Inc
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Filing: 1976-07-26
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Granted: 1977-11-08
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Expires: 1996-07-26
Abstract
Abstract A graded index optical fiber waveguide for use in an optical communication system is disclosed. The waveguide is a circular symmetric fiber having a cladding with an index of refraction n 2 surrounding a core whose index of refraction is graded from an on axis value of n 1 to a value of n 2 at the core-cladding interface. The index of refraction within the core is defined in terms of a profile function F by the following equation n.sup.2 = n.sub.1.sup.2 (1-F) where F is O on the axis and a function of the radial coordinate r and wavelength λ within the core and satisfies the following equation ##EQU1## where D is a function of λ having a value approximately equal to 2 for minimum modal dispersion and ##EQU2## IS THE GROUP INDEX ON AXIS. The modal dispersion achieved with this design is only a function of n 1 - n 2 and is independent of the profile dispersion ##EQU3##
Inventors
- 👤 Enrique Alfredo Jose Marcatili
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:20
CPC Classifications
G; G02; G02B; G02B6/00; G02B6/02; G02B6/02214; G02B6/02285; G02B6/028; G02B6/0288
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
158 words
A circular-symmetric optical fiber waveguide comprising a core surrounded by a layer of cladding material, the refractive index of said layer n 2 being less than n 1 , the value of the index of refraction on the axis of the core, and the index of refraction n in said core is graded in accordance with the following equation n.sup.2 = n.sub.1.sup.2 (1-F), where F is a profile function equal to zero on the axis and equal to (n 1 2 - n 2 2 )/n 1 2 at the core-cladding interface, characterized in that the profile dispersion is a non-constant value with respect to radius given by the following equation ##EQU36## N 1 is the group index on axis, λ is the wavelength, and the profile function F is related to the radial coordinate r and the profile dispersion substantially in accordance with the following equation ##EQU37## where D is a dispersion parameter approximately equal to 2.
Claim 2
Dependent Claim
158 words
A circular-symmetric optical fiber waveguide comprising a core surrounded by a layer of cladding material, the refractive index of said layer n 2 being less than n 1 , the value of the index of refraction on the axis of the core, and the index of refraction n in said core is graded in accordance with the following equation n.sup.2 = n.sub.1.sup.2 (1-F), where F is a profile function equal to zero on the axis and equal to (n 1 2 - n 2 2 )/n 1 2 at the core-cladding interface, characterized in that the profile dispersion is a non-constant value with respect to radius given by the following equation ##EQU36## N 1 is the group index on axis, λ is the wavelength, and the profile function F is related to the radial coordinate r and the profile dispersion substantially in accordance with the following equation ##EQU37## where D is a dispersion parameter approximately equal to 2.
Claim 3
Dependent Claim
79 words
An optical fiber waveguide in accordance with claim 1 wherein the frequency range of operation is small such that D is substantially a constant value, and each value of F in the index profile is positioned at a radial coordinate r determined in accordance with the following equation ##EQU38## where Δ is equal to (n 1 2 - n 2 2 )/2n 1 2 and the profile function F has a value equal to 2Δ at the core-cladding interface.
Claim 4
Dependent Claim
35 words
An optical fiber waveguide in accordance with claim 1 where D is equal to 1 + √1 - 2Δ, and Δ is equal to (n 1 2 - n 2 2 )/2n 1 2 .
Claim 5
Dependent Claim
22 words
An optical fiber waveguide as defined in claim 3 wherein Δ << 1 and D is approximately equal to 2 - Δ.
Claim 6
Dependent Claim
61 words
An optical fiber waveguide as defined in claim 1 wherein minimum modal dispersion is achieved over a larger band of wavelengths by choosing the profile function and profile dispersion to satisfy the following equation ##EQU39## where D o is approximately equal to 1 + √1 - 2Δ and Δ = (n 1 2 - n 2 2 )/2n 1 2 .
Claim 7
Dependent Claim
164 words
A circular symmetric optical fiber waveguide comprising a core having a radius a and an index of refraction n having a value equal to n 1 on the axis of the core, a layer of cladding material surrounding said core the refractive index of said layer being less than n 1 , said core having an index grading such that a maximum amount of index-increasing dopant is present on the axis of said core and a maximum amount of index-decreasing dopant is present at the core-cladding interface, characterized in that the profile dispersion of the material in said core is a nonconstant value with respect to radius and is defined by the following relationship ##EQU40## where N 1 is the group index on the axis and F is the profile function defined by the following relationship n.sup.2 = n.sub.1.sup.2 (1-F), and the profile dispersion is related to the profile function in accordance with the following relationship ##EQU41## where D is approximately equal to 2.
Claim 8
Dependent Claim
164 words
A circular symmetric optical fiber waveguide comprising a core having a radius a and an index of refraction n having a value equal to n 1 on the axis of the core, a layer of cladding material surrounding said core the refractive index of said layer being less than n 1 , said core having an index grading such that a maximum amount of index-increasing dopant is present on the axis of said core and a maximum amount of index-decreasing dopant is present at the core-cladding interface, characterized in that the profile dispersion of the material in said core is a nonconstant value with respect to radius and is defined by the following relationship ##EQU40## where N 1 is the group index on the axis and F is the profile function defined by the following relationship n.sup.2 = n.sub.1.sup.2 (1-F), and the profile dispersion is related to the profile function in accordance with the following relationship ##EQU41## where D is approximately equal to 2.
Claim 9
Dependent Claim
19 words
An optical fiber waveguide as defined in claim 6 wherein D is equal to 1 + √1 - 2Δ.
Claim 10
Dependent Claim
22 words
An optical fiber waveguide as defined in claim 6 wherein Δ < < 1, and d is equal to 2 - Δ.
References Cited (Backward Citations)
US3904268A
Cited
US4006962A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-11-07 | 1981-05-09 | 1981-11-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-11-07 | 1985-05-09 | 1985-11-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-11-07 | 1989-05-09 | 1989-11-08 | $7700.00 | Window Closed / Lapsed |