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US4181433A
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Method for determining the refractive index profile of optical fibers and optical fiber preforms
Assignee: AT&T Inc
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Filing: 1978-04-14
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Granted: 1980-01-01
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Expires: 1998-04-14
Abstract
Abstract This application describes a nondestructive method for determining the refractive index profile of optical fibers and fiber preforms by measuring the density distribution of the light that is focused by the fiber/preform core acting as the lens. The fiber/preform is immersed in an index matching medium and illuminated by means of a collimated light beam directed at right angles to the fiber/preform axis. The density distribution of the light focused by the fiber/preform core is then measured along a direction normal to the fiber/preform axis at a distance L from the axis that is less than the focal length of the fiber/preform. The index profile is determined from these measurements by two numerical integrations.
Inventors
- 👤 Dietrich Marcuse
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 15:04
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/17; G01N21/41; G01N21/412
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
97 words
A method for determining the refractive index profile of an optical fiber and an optical fiber preform comprising the steps of: immersing said fiber/preform in an index matching medium; illuminating said fiber/preform; measuring, along a direction transverse to the longitudinal axis of said fiber/preform, the intensity distribution of radiant energy focused by said fiber/preform; CHARACTERIZED IN THAT said measurement is made at a distance from the center of said fiber/preform that is less than the focal length of said fiber/preform; and by the further step of determining from said measurement the refractive index profile of said fiber/preform.
Claim 2
Independent Claim
97 words
A method for determining the refractive index profile of an optical fiber and an optical fiber preform comprising the steps of: immersing said fiber/preform in an index matching medium; illuminating said fiber/preform; measuring, along a direction transverse to the longitudinal axis of said fiber/preform, the intensity distribution of radiant energy focused by said fiber/preform; CHARACTERIZED IN THAT said measurement is made at a distance from the center of said fiber/preform that is less than the focal length of said fiber/preform; and by the further step of determining from said measurement the refractive index profile of said fiber/preform.
Claim 3
Dependent Claim
124 words
The method according to claim 1 CHARACTERIZED IN THAT: the index profile n(r) is given by ##EQU4## where n c is the refractive index of the fiber/preform cladding; a is the radius of the fiber/preform core; L is the distance from the fiber/preform core center at which the measurements are made; r is the radial distance from the center of the fiber-preform core; and y(t) is the function that defines the position of an output ray at the measuring plane as a function of the position (t) of the corresponding input ray, and is the inverse of the function t(y) given by ##EQU5## P(y') is the measured light intensity along the measuring plane; and the output light is confined within the index matching medium.
Claim 4
Dependent Claim
128 words
The method according to claim 1 CHARACTERIZED IN THAT the index profile n(r) is given by ##EQU6## where n c is the refractive index of the fiber/preform cladding; a is the radius of the fiber/preform core; L is the distnace from the fiber/preform core center at which the measurements are made; r is the radial distance from the center of the fiber-preform core; and y(t) is the function that defines the position of an output ray at the measuring plane as a function of the position (t) of the corresponding input ray and is the inverse of the function t(y) given by ##EQU7## where P(y') is the measured light intensity along the measuring plane; and the output light leaves the index matching medium before entering the measuring means.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-12-31 | 1983-07-02 | 1984-01-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-12-31 | 1987-07-02 | 1988-01-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-12-31 | 1991-07-02 | 1992-01-01 | $7700.00 | Window Closed / Lapsed |