US4699464A
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BeF2 -based optical fibers
Assignee: Nokia Bell Labs
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Filing: 1986-02-20
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Granted: 1987-10-13
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Expires: 2006-02-20
Abstract
Abstract Disclosed is BeF 2 -based optical fiber. Such fiber can have, in addition to low loss, other advantageous properties. For instance, BeF 2 -based dispersion shifted single mode fiber can have lower core-cladding index difference and larger core diameter than the corresponding SiO 2 -based fiber, and BeF 2 -based graded index multimode fiber can have larger bandwidth than the corresponding SiO 2 -based fiber. The inventive fibers have a core and a cladding containing at least 30 mol % BeF 2 , and may contain up to 40 mol % of AlF 3 , and one or more members of the group consisting of NaF, KF, MgF 2 , CaF 2 , PbF 2 , PF 5 , and SiF 4 . An exemplary and currently preferred glass has nominal composition (in mol percent) 30KF-(15-x)CaF 2 -xPbF 2 -10AlF 3 -45BeF 2 , with x≦15. Single mode fibers according to the invention have minimum total dispersion in the range 1.5-2.0 μm, and typically have 0.25%≦Δ esi ≦0.6%, and 2.5 μm≦a esi ≦3.4 μm, where Δ esi and a esi are the equivalent step index core-cladding index difference and core radius, respectively. Rules and techniques that can advantageously be used to design BeF 2 -based single mode fibers are also disclosed.
Inventors
- 👤 Leonard G. Cohen
- 👤 James W. Fleming
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 21:08
CPC Classifications
G; G02; G02B; G02B6/00; G02B6/02; G02B6/02214; G02B6/02219; G02B6/02228; G02B6/02233; C; C03; C03C; C03C13/00; C03C13/04; C03C13/041; C03C13/042; G02B6/10; G02B6/102
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
211 words
A single mode optical fiber comprising a core and a first cladding contactingly surrounding the core, the core having a radius a and a maximum index of refraction n 1 <n s , where n s is the refractive index of fused silica, the first cladding having a refractive index n 2 , with n 2 <n 1 , the fiber having minimum total dispersion at wavelength λ o and minimum material dispersion at λ m <λ o , and associated with the fiber is a refractive index profile and a profile exponent α, with 1<α≦∞, an equivalent step index core-cladding index difference Δ esi , and an equivalent step index core radius a esi , characterized in that (a) at least the fiber core and the first cladding consist substantially of a glass that comprises at least 30 mol% BeF 2 ; (b) 1.5≦λ o ≦2 μm; (c) 0.5Δ s ≦Δ esi <Δ s ; and (d) a esi >a s n s /n 2 ; wherein Δ s and a s are the refractive index difference and the core radius, respectively, of a silica-based step-index reference fiber having minimum total dispersion at wavelength λ o , with all quantities in (c) and (d) referring to wavelength λ o .
Claim 2
Dependent Claim
211 words
A single mode optical fiber comprising a core and a first cladding contactingly surrounding the core, the core having a radius a and a maximum index of refraction n 1 <n s , where n s is the refractive index of fused silica, the first cladding having a refractive index n 2 , with n 2 <n 1 , the fiber having minimum total dispersion at wavelength λ o and minimum material dispersion at λ m <λ o , and associated with the fiber is a refractive index profile and a profile exponent α, with 1<α≦∞, an equivalent step index core-cladding index difference Δ esi , and an equivalent step index core radius a esi , characterized in that (a) at least the fiber core and the first cladding consist substantially of a glass that comprises at least 30 mol% BeF 2 ; (b) 1.5≦λ o ≦2 μm; (c) 0.5Δ s ≦Δ esi <Δ s ; and (d) a esi >a s n s /n 2 ; wherein Δ s and a s are the refractive index difference and the core radius, respectively, of a silica-based step-index reference fiber having minimum total dispersion at wavelength λ o , with all quantities in (c) and (d) referring to wavelength λ o .
Claim 3
Dependent Claim
18 words
Optical fiber of claim 1, wherein the glass further comprises up to about 40 mol% AlF 3 .
Claim 4
Dependent Claim
63 words
Optical fiber of claim 2, wherein the glass further comprises at least one member of the fluoride group consisting of NaF, KF, MgF 2 , CaF 2 , PbF 2 , PF 5 , and SiF 4 , with BeF 2 , AlF 3 , and the at least one member of the fluoride group constituting at least 95 mol% of the glass.
Claim 5
Dependent Claim
51 words
Optical fiber of claim 3, wherein the glass is substantially of composition wX-(30-x)CaF 2 -xPbF 2 -yAlF 3 -zBeF 2 , with X being at least one member of the group consisting of KF, MgF 2 , and NaF, and wherein 0<w≦40%, 0≦x≦30%, 0<y≦20%, and 30≦z≦60%, all percentages being mol percent.
Claim 6
Dependent Claim
23 words
Optical fiber of claim 4, wherein the glass is substantially of composition 30KF-(15-x')CaF 2 -x'PbF 2 -10AlF 3 -45BeF 2 , with 0≦x'≦15.
Claim 7
Dependent Claim
21 words
Optical fiber of claim 1, wherein a esi =(a s n s /n 2 )(Δ s /Δ esi ) 1/2 .
Claim 8
Dependent Claim
132 words
A single mode optical fiber comprising a core and a first cladding contactingly surrounding the core, the core having a radius a and a maximum index of refraction n 1 , the first cladding having a refractive index n 2 <n 1 , the fiber having minimum total dispersion at a wavelength λ o and minimum material dispersion at λ m <λ o , and associated with the fiber is an equivalent step index core radius a esi and an equivalent step index core-cladding index difference Δ esi ; characterized in that (a) at least the fiber core and the first cladding consist substantially of a glass that comprises at least 30 mol% BeF 2 ; (b) 1.5≦λ o ≦2 μm; (c) 0.25%≦Δ esi ≦0.6%; and (d) 2.5 μm≦a esi ≦3.4 μm.
Claim 9
Dependent Claim
132 words
A single mode optical fiber comprising a core and a first cladding contactingly surrounding the core, the core having a radius a and a maximum index of refraction n 1 , the first cladding having a refractive index n 2 <n 1 , the fiber having minimum total dispersion at a wavelength λ o and minimum material dispersion at λ m <λ o , and associated with the fiber is an equivalent step index core radius a esi and an equivalent step index core-cladding index difference Δ esi ; characterized in that (a) at least the fiber core and the first cladding consist substantially of a glass that comprises at least 30 mol% BeF 2 ; (b) 1.5≦λ o ≦2 μm; (c) 0.25%≦Δ esi ≦0.6%; and (d) 2.5 μm≦a esi ≦3.4 μm.
Claim 10
Dependent Claim
107 words
A multimode optical fiber comprising a core and a first cladding contactingly surrounding the core, the core having a refractive index n 1 , the first cladding having a maximum refractive index n 2 <n 1 , and a core-cladding index difference Δ, the fiber having maximum bandwidth at λ m , characterized in that (a) at least the fiber core and the first cladding consist substantially of a glass that comprises at least 30 mol% BeF 2 ; (b) the bandwidth of the fiber is greater than (1.7Δ) GHz km for all wavelengths λ in the range |λ-λ m |≦0.2 μm, with Δ being in percent.
Claim 11
Dependent Claim
107 words
A multimode optical fiber comprising a core and a first cladding contactingly surrounding the core, the core having a refractive index n 1 , the first cladding having a maximum refractive index n 2 <n 1 , and a core-cladding index difference Δ, the fiber having maximum bandwidth at λ m , characterized in that (a) at least the fiber core and the first cladding consist substantially of a glass that comprises at least 30 mol% BeF 2 ; (b) the bandwidth of the fiber is greater than (1.7Δ) GHz km for all wavelengths λ in the range |λ-λ m |≦0.2 μm, with Δ being in percent.
Claim 12
Dependent Claim
72 words
Multimode optical fiber of claim 8, wherein the glass substantially has the composition wX-(30-x)CaF 2 -xPbF 2 -yAlF 3 -zBeF 2 , with X being at least one member of the group consisting of KF, MgF 2 , and NaF, and wherein 0<w≦40%, 0≦x≦30%, 0<y≦20%, and 30≦z≦60%, all percentages being mol percent, and wherein the bandwidth of the fiber is greater than 2Δ GHz·km for all λ in |λ-λ m |≦0.2 μm.
Claim 13
Dependent Claim
22 words
Multimode optical fiber of claim 9, wherein the glass is substantially of composition 30KF-(15-x')CaF 2 -x'PbF 2 -45BeF 2 , with x'≦15.
References Cited (Backward Citations)
US4328318A
Cited
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| 3.5 Years (Year 4) | 1990-10-12 | 1991-04-13 | 1991-10-13 | $2000.00 | Window Closed / Lapsed |
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