US3982816A
Expired / Lapsed
US
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Method for measuring the parameters of optical fibers
Assignee: AT&T Inc
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Filing: 1974-06-21
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Granted: 1976-09-28
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Expires: 1994-06-21
Abstract
Abstract Parameters of a clad optical fiber are measured by irradiating the fiber with a laser beam to generate a scattering pattern. Measurements are made of fringes and modulations in the scattering pattern and these measurements are translated into such parameters as core and fiber diameter.
Inventors
- 👤 Laurence Shrapnell Watkins
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 13:16
CPC Classifications
G; G01; G01M; G01M11/00; G01M11/30; G01M11/37; G01B; G01B11/00; G01B11/08
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
168 words
A method of measuring the outer diameter of an optical fiber having an inner core and an outer cladding, given the refractive index of the outer cladding, which comprises: directing a beam of coherent, monochromatic radiation at the fiber to generate a far-field scattering pattern, a portion of the scattering pattern resulting from interference between radiation reflected from the outer surface of the fiber and radiation predominated by light passing through and being refracted by the outer cladding; counting the number, N, of fringes between a lower scattering angle θ 1 and upper scattering angle θ 2 in said portion of the scattering pattern; and calculating the outer diameter, d, of the fiber from the relation d = Nλ/[ E(θ.sub.2) - E(θ.sub.1)] wherein E(θ.sub.1) = sin (θ.sub.1 /2) + √m.sub.1.sup.2 + 1 - 2m.sub.1 cos (θ.sub.1 /2) E(θ.sub.2) = sin (θ.sub.2 /2) + √m.sub.1.sup.2 + 1 - 2m.sub.1 cos (θ.sub.2 /2) m 1 = the refractive index of the cladding, and λ = the wavelength of the radiation.
Claim 2
Independent Claim
168 words
A method of measuring the outer diameter of an optical fiber having an inner core and an outer cladding, given the refractive index of the outer cladding, which comprises: directing a beam of coherent, monochromatic radiation at the fiber to generate a far-field scattering pattern, a portion of the scattering pattern resulting from interference between radiation reflected from the outer surface of the fiber and radiation predominated by light passing through and being refracted by the outer cladding; counting the number, N, of fringes between a lower scattering angle θ 1 and upper scattering angle θ 2 in said portion of the scattering pattern; and calculating the outer diameter, d, of the fiber from the relation d = Nλ/[ E(θ.sub.2) - E(θ.sub.1)] wherein E(θ.sub.1) = sin (θ.sub.1 /2) + √m.sub.1.sup.2 + 1 - 2m.sub.1 cos (θ.sub.1 /2) E(θ.sub.2) = sin (θ.sub.2 /2) + √m.sub.1.sup.2 + 1 - 2m.sub.1 cos (θ.sub.2 /2) m 1 = the refractive index of the cladding, and λ = the wavelength of the radiation.
Claim 3
Dependent Claim
44 words
The method according to claim 1 wherein said beam directing step comprises: positioning the beam of spatially coherent, monochromatic radiation to impinge upon said filament perpendicular to the longitudinal axis thereof, said beam having an electric field vector which is parallel to said axis.
Claim 4
Dependent Claim
44 words
The method according to claim 1 wherein said beam directing step comprises: positioning the beam of spatially coherent, monochromatic radiation to impinge upon said filament perpendicular to the longitudinal axis thereof, said beam having an electric field vector which is transverse to said axis.
Claim 5
Dependent Claim
41 words
The method of claim 1 wherein θ 1 > θ C , where θ C is the scattering angle below which substantially all the refracted radiation contributing to the scattering pattern passes through both the inner core and the outer cladding.
Claim 6
Dependent Claim
15 words
The method of claim 1 wherein θ 2 < 2 cos.sup. -1 (1/m 1 ).
Claim 7
Dependent Claim
23 words
The method of claim 1 wherein the ratio of core diameter to fiber diameter, a/b, satisfies the inequality a/b < 1/m 1 .
Claim 8
Independent Claim
190 words
A method of measuring the ratio between the core diameter and the outer diameter of an optical fiber having an inner core and an outer cladding, given the refractive index of the outer cladding, which comprises: directing a beam of coherent, monochromatic radiation at the fiber to generate a far-field scattering pattern, a portion of the scattering pattern resulting from interference between radiation reflected from the outer surface of the fiber and radiation passing through and being refracted by the fiber; fringes in a part of said portion of the scattering pattern being modulated by interference between radiation refracted by both the inner core and the outer cladding and radiation refracted only by the outer cladding; measuring the angle θ C where said modulation begins and below which substantially all the refracted light contributing to the scattering pattern passes through both the inner core and the outer cladding; and calculating the ratio a/b from the relation a/b = sin (θ.sub.C /2)/ √m.sub.1.sup.2 + 1 - 2m.sub.1 cos (θ.sub.C /2) wherein a = the core diameter, b = the outer diameter, and m 1 = the refractive index of the cladding.
Claim 9
Independent Claim
190 words
A method of measuring the ratio between the core diameter and the outer diameter of an optical fiber having an inner core and an outer cladding, given the refractive index of the outer cladding, which comprises: directing a beam of coherent, monochromatic radiation at the fiber to generate a far-field scattering pattern, a portion of the scattering pattern resulting from interference between radiation reflected from the outer surface of the fiber and radiation passing through and being refracted by the fiber; fringes in a part of said portion of the scattering pattern being modulated by interference between radiation refracted by both the inner core and the outer cladding and radiation refracted only by the outer cladding; measuring the angle θ C where said modulation begins and below which substantially all the refracted light contributing to the scattering pattern passes through both the inner core and the outer cladding; and calculating the ratio a/b from the relation a/b = sin (θ.sub.C /2)/ √m.sub.1.sup.2 + 1 - 2m.sub.1 cos (θ.sub.C /2) wherein a = the core diameter, b = the outer diameter, and m 1 = the refractive index of the cladding.
Claim 10
Dependent Claim
17 words
The method of claim 7 wherein the ratio a/b satisfies the inequality a/b < 1/m 1 .
Claim 11
Dependent Claim
44 words
The method according to claim 7 wherein said beam directing step comprises: positioning the beam of spatially coherent, monochromatic radiation to impinge upon said filament perpendicular to the longitudinal axis thereof, said beam having an electric field vector which is parallel to said axis.
Claim 12
Dependent Claim
44 words
The method according to claim 7 wherein said beam directing step comprises: positioning the beam of spatially coherent, monochromatic radiation to impinge upon said filament perpendicular to the longitudinal axis thereof, said beam having an electric field vector which is transverse to said axis.
Claim 13
Independent Claim
210 words
A method of measuring the core diameter of an optical fiber having an inner core and an outer cladding, given the outer diameter of the fiber and the refractive index of the outer cladding, which comprises: a. directing a beam of coherent, monochromatic radiation at the fiber to generate a far-field scattering pattern, a portion of the scattering pattern resulting from radiation reflected from the outer surface of the fiber and radiation passing through and being refracted by the fiber; fringes in a part of said portion of the scattering pattern being modulated by interference between radiation refracted by both the inner core and the outer cladding and radiation refracted only by the outer cladding; b. measuring the angle θ C where said modulation begins and below which substantially all the refracted light contributing to the scattering pattern passes through both the inner core and the outer cladding; c. calculating the ratio a/b from the relation a/b = sin (θ.sub.C /2)/ √m.sub.1.sup.2 + 1 - 2m.sub.1 cos (θ.sub.C /2) wherein a = the core diameter, b = the outer diameter, m 1 = the refractive index of the cladding; and d. calculating the core diameter a from the given fiber diameter b and the ratio a/b calculated in step (c).
Claim 14
Independent Claim
210 words
A method of measuring the core diameter of an optical fiber having an inner core and an outer cladding, given the outer diameter of the fiber and the refractive index of the outer cladding, which comprises: a. directing a beam of coherent, monochromatic radiation at the fiber to generate a far-field scattering pattern, a portion of the scattering pattern resulting from radiation reflected from the outer surface of the fiber and radiation passing through and being refracted by the fiber; fringes in a part of said portion of the scattering pattern being modulated by interference between radiation refracted by both the inner core and the outer cladding and radiation refracted only by the outer cladding; b. measuring the angle θ C where said modulation begins and below which substantially all the refracted light contributing to the scattering pattern passes through both the inner core and the outer cladding; c. calculating the ratio a/b from the relation a/b = sin (θ.sub.C /2)/ √m.sub.1.sup.2 + 1 - 2m.sub.1 cos (θ.sub.C /2) wherein a = the core diameter, b = the outer diameter, m 1 = the refractive index of the cladding; and d. calculating the core diameter a from the given fiber diameter b and the ratio a/b calculated in step (c).
Claim 15
Dependent Claim
17 words
The method of claim 11 wherein the ratio a/b satisfies the inequality a/b < 1/m 1 .
Claim 16
Dependent Claim
44 words
The method according to claim 11 wherein said beam directing step comprises: positioning the beam of spatially coherent, monochromatic radiation to impinge on said filament perpendicular to the longitudinal axis thereof, said beam having an electric field vector which is parallel to said axis.
Claim 17
Dependent Claim
44 words
The method according to claim 11 wherein said beam directing step comprises: positioning the beam of spatially coherent, monochromatic radiation to impinge on said filament perpendicular to the longitudinal axis thereof, said beam having an electric field vector which is transverse to said axis.
Claim 18
Independent Claim
195 words
A method of measuring a change in the outer diameter of a continuously advancing optical fiber having an inner core and an outer cladding, given the refractive index of the outer cladding, which comprises: directing a beam of coherent monochromatic radiation at the filament to generate a far-field scattering pattern, a portion of the scattering pattern resulting from interference between radiation reflected from the outer surface of the fiber and radiation predominated by light passing through and being refracted by the outer cladding; at a scattering angle θ R in said portion of the pattern, counting the number, N p , of fringes that pass as the filament advances a given distance; calculating the diameter change, δd, in the given distance from the relation δd = λN.sub.p /[ sin (θ.sub.R /2) + √m.sub.1.sup.2 + 1 - 2m.sub.1 cos (θ.sub.R /2)] wherein m 1 = the refractive index of the cladding, and λ = the wavelength of the light; and wherein θ R > θ C , where θ C is the scattering angle below which substantially all the refracted radiation contributing to the scattering pattern passes through both the inner core and the outer cladding.
Claim 19
Independent Claim
195 words
A method of measuring a change in the outer diameter of a continuously advancing optical fiber having an inner core and an outer cladding, given the refractive index of the outer cladding, which comprises: directing a beam of coherent monochromatic radiation at the filament to generate a far-field scattering pattern, a portion of the scattering pattern resulting from interference between radiation reflected from the outer surface of the fiber and radiation predominated by light passing through and being refracted by the outer cladding; at a scattering angle θ R in said portion of the pattern, counting the number, N p , of fringes that pass as the filament advances a given distance; calculating the diameter change, δd, in the given distance from the relation δd = λN.sub.p /[ sin (θ.sub.R /2) + √m.sub.1.sup.2 + 1 - 2m.sub.1 cos (θ.sub.R /2)] wherein m 1 = the refractive index of the cladding, and λ = the wavelength of the light; and wherein θ R > θ C , where θ C is the scattering angle below which substantially all the refracted radiation contributing to the scattering pattern passes through both the inner core and the outer cladding.
Claim 20
Dependent Claim
15 words
The method of claim 15 wherein θ R < 2 cos.sup. -1 (1/m 1 ).
Claim 21
Dependent Claim
23 words
The method of claim 15 wherein the ratio of core diameter to fiber diameter, a/b, satisfies the inequality a/b < 1/m 1 .
Claim 22
Dependent Claim
44 words
The method according to claim 15 wherein said beam directing step comprises: positioning the beam of spatially coherent, monochromatic radiation to impinge on said filament perpendicular to the longitudinal axis thereof, said beam having an electric field vector which is parallel to said axis.
Claim 23
Dependent Claim
44 words
The method according to claim 15 wherein said beam directing step comprises: positioning the beam of spatially coherent, monochromatic radiation to impinge on said filament perpendicular to the longitudinal axis thereof, said beam having an electric field vector which is transverse to said axis.
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) | 1979-09-28 | 1980-03-29 | 1980-09-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-09-28 | 1984-03-29 | 1984-09-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-09-28 | 1988-03-29 | 1988-09-28 | $7700.00 | Window Closed / Lapsed |