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US4447124A
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Multimode optical fiber with radially varying attenuation center density
Assignee: AT&T Inc
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Filing: 1981-10-27
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Granted: 1984-05-08
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Expires: 2001-10-27
Abstract
Abstract The inventive multimode fiber has total loss at an operating wavelength of at least about 0.8 db/km, typically not more than 5 db/km. At least 0.3 db/km, preferably 0.5 db/km, of the loss is due to the presence in the fiber of radially nonuniformly distributed attenuation centers, with the concentration of the centers differing by at least about 10% between the concentration minimum and the maximum. The resulting differential mode attenuation can lead to fiber having larger bandwidth than analogous fiber without differential attenuation. Preferred distributions of attenuation centers have the concentration maximum either at or near the fiber axis, or at or near the core/clad interface. Preferred attenuation centers are absorbers, with OH being a preferred absorber. The fiber is produced by a method comprising a procedure designed to result in the above-described distribution of attenuation centers, typically by maintaining the distribution introduced into the preform during preform production, or by deliberate introduction of attenuation centers into the preform during preform production.
Inventors
- 👤 Leonard G. Cohen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 20:05
CPC Classifications
C; C03; C03C; C03C13/00; C03C13/04; C03C13/045; C03B; C03B37/00; C03B37/01; C03B37/012; C03B37/01205; C03B37/01225; C03B37/01248; C03B37/014; C03B37/01446; C03B37/018; C03B37/01861; C03B37/01869; C03B37/02; C03B37/025; C03B37/027; G; G02; G02B; G02B6/00; G02B6/02; C03B2201/00; C03B2201/06; C03B2201/20; C03B2201/23; C03B2203/00; C03B2203/10; C03B2203/22; C03B2203/36
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
87 words
Multimode optical fiber for transmitting signals at least at a first wavelength, the fiber comprising a core and a clad and having a loss at the first wavelength of at least about 0.8 db/km, with a loss of at least about 0.3 db/km being caused by the presence of attenuation centers in the core, characterized in that the core has a radially varying attenuation center concentration profile in at least part of the fiber, with the maximum concentration exceeding the minimum concentration by at least about 10%.
Claim 2
Dependent Claim
87 words
Multimode optical fiber for transmitting signals at least at a first wavelength, the fiber comprising a core and a clad and having a loss at the first wavelength of at least about 0.8 db/km, with a loss of at least about 0.3 db/km being caused by the presence of attenuation centers in the core, characterized in that the core has a radially varying attenuation center concentration profile in at least part of the fiber, with the maximum concentration exceeding the minimum concentration by at least about 10%.
Claim 3
Dependent Claim
22 words
Optical fiber according to claim 1 wherein the fiber has a loss at the first wavelength not larger than about 5 db/km.
Claim 4
Dependent Claim
25 words
Optical fiber according to claim 2 wherein the attenuation centers consist substantially of centers that absorb electromagnetic radiation at some wavelengths including the first wavelength.
Claim 5
Dependent Claim
23 words
Optical fiber according to claim 3 wherein the maximum of the attenuation center profile is located substantially at the center of the core.
Claim 6
Dependent Claim
21 words
Optical fiber according to claim 3 wherein the maximum of the attenuation center profile is located substantially at the core/clad interface.
Claim 7
Dependent Claim
16 words
Optical fiber according to claim 4 or 5 wherein the attenuation centers consist substantially of OH.
Claim 8
Dependent Claim
146 words
Method for producing multimode optical fiber having a core and a clad and a loss at a first wavelength of at least about 0.8 db/km, with a loss of at least about 0.3 db/km being caused by the presence of attenuation centers in the core, the method comprising drawing a fiber from a preform, characterized in that the method further comprises a procedure designed to result in a radially varying attenuation center profile in the fiber core in at least part of the fiber drawn from the preform, with the maximum concentration in the core exceeding the minimum concentration in the core by at least about 10%, the procedure selected from the group of procedures consisting of (1) deliberately introducing the attenuation centers into the preform during production of the preform, and (2) substantially maintaining a radially varying distribution of attenuation centers existing in the preform.
Claim 9
Dependent Claim
146 words
Method for producing multimode optical fiber having a core and a clad and a loss at a first wavelength of at least about 0.8 db/km, with a loss of at least about 0.3 db/km being caused by the presence of attenuation centers in the core, the method comprising drawing a fiber from a preform, characterized in that the method further comprises a procedure designed to result in a radially varying attenuation center profile in the fiber core in at least part of the fiber drawn from the preform, with the maximum concentration in the core exceeding the minimum concentration in the core by at least about 10%, the procedure selected from the group of procedures consisting of (1) deliberately introducing the attenuation centers into the preform during production of the preform, and (2) substantially maintaining a radially varying distribution of attenuation centers existing in the preform.
Claim 10
Dependent Claim
21 words
Method according to claim 7 wherein the fiber has a loss at the first wavelength not larger than about 5 db/km.
Claim 11
Dependent Claim
23 words
Method of claim 8, wherein the attenuation centers consist substantially of centers that absorb electromagnetic radiation at some wavelengths including the first wavelength.
Claim 12
Dependent Claim
24 words
Mehtod of claim 9, wherein at least a substantial part of the absorbing centers are introduced during collapsing the preform into a solid preform.
Claim 13
Dependent Claim
24 words
Method of claim 9, wherein at least a substantial part of the absorbing centers are introduced during drawing of the fiber from the preform.
Claim 14
Dependent Claim
14 words
Method of claim 10 or 11, wherein the attenuation centers consist substantially of OH.
Claim 15
Dependent Claim
10 words
Multimode optical fiber produced by the method of claim 7.
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) | 1987-05-08 | 1987-11-07 | 1988-05-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-05-08 | 1991-11-07 | 1992-05-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-05-08 | 1995-11-07 | 1996-05-08 | $7700.00 | Window Closed / Lapsed |