US 9,804,325 B2Granted

Framework for the design of optimum and near-optimum broadband multi-mode optical fibers by core doping

AssigneeOFS Fitel, LLC

InventorKasyapa Balemarthy

Life of this patent

Estimating the term…

Abstract

Described is a technique for optimizing the design and manufacture of broadband MMFs. MMFs for use in CWDM applications are specifically described.

Claims9

Dependent claims

A broadband multimode optical fiber comprising:

a core region having a transverse cross-section and a longitudinal axis, said core region being configured for broadband operation at wavelengths λ within a predetermined wavelength range, Λ, and
a cladding region surrounding said core region,
said core and cladding regions being configured to support the propagation of optical radiation in said core region and along said axis simultaneously in a plurality of transverse modes,
said core region having a refractive index profile n(r,λ) and being co-doped with I different dopants having concentration profiles Xi(r), i=1, 2, . . . I, the concentrations and distributions of said dopants being radially varied within said transverse cross-section of said core region so that the refractive index of said core region is radially graded and so that variations in z(r,λ) with respect to wavelength are reduced, where
z(r,λ)n2(r,λ)k02,
r is radius, λ is the wavelength of said optical radiation, n is the refractive index of said core region,
k
0
=
2
⁢
π
λ
is the wave number, and wherein said concentrations and distribution of said dopants are also radially varied within said transverse cross-section of said core region so that said dopant concentration profiles are configured by the following criteria:
(a) a profile function ƒ(r,λ) is defined by ƒ(r,λ)=z0−z(r,λ), z0=z(r=0,λ),
(b) ƒ(r=0,λ)=ƒ0=0, ƒ(r=a,λ)=ƒa=(NA·k0)2, where NA is the numerical aperture of the fiber and equation (b) satisfies equation (c) below,
f
(
i
-
1
)
+
r
2
⁢
∂
f
(
i
-
1
)
∂
r
=
[
df
⁢
(
1
)
]
(
i
-
1
)
,
i
=
1
,
2
,
…
⁢
,
I
,
(
c
)
where the ith order derivative of a quantity x with respect to k0 is denoted by
x
(
i
)
=
∂
i
⁢
x
∂
⁢
k
0
i
and the parameter d is given by
d
=
Dz
0
z
0
(
1
)
;
and
(d) said profile function ƒ(r,λ) is related to said dopant concentration profiles Xi(r), t=1, 2, . . . , I by
f
⁡
(
r
,
k
0
)
=
∑
i
=
1
I
⁢
x
i
⁡
(
r
)
⁢
e
i
⁡
(
k
0
)
,
x
i
⁡
(
r
)
=
X
i
⁡
(
r
=
0
)
-
X
i
⁡
(
r
)
with ei(k0)=ziR(k0)−zS(k0) where ziR(k0) is the z due to a reference amount of dopant concentration for dopant i and zS is the z due to pure silica.

141 more elements

A method of fabricating an optimum broadband multimode optical fiber comprising the steps of:

(a) determining desired performance characteristics of the fiber, including at least a core region and a cladding region surrounding said core region, said core region having a refractive index n(r,λ),
(b) determining desired structural characteristics of the fiber,
(c) determining the numerical aperture and bandwidth of the fiber,
(d) determining I different dopants that will be incorporated into the core region of the fiber, each of said dopants being, characterized by a dopant concentration profile,
(e) setting up a numerical code to generate the dopant concentration profiles of each of said dopants by reducing the variation of z(r,λ) with respect to wavelength, where z(r,λ)n2(r,λ)k02, r is radius, λ is wavelength, and
k
0
=
2
⁢
⁢
π
λ
is the wave number,
(f) setting up a numerical code to generate a profile function ƒ(r,λ) defined by ƒ(r,λ)=z0−z(r,λ), z0=z(r=0,λ) and ƒ(r=0,λ)=ƒ0=0, ƒ(r=a,λ)=ƒ0=(NA·k0)2, where NA is the numerical aperture of the MMF and r=a is radius of said core region, said profile function satisfying equation (g) below,
(g) setting up a numerical code to generate
f
(
i
-
1
)
+
r
2
⁢
∂
f
(
i
-
1
)
∂
r
=
[
df
⁢
(
1
)
]
(
i
-
1
)
,
i
=
1
,
2
,
…
⁢
,
I
,
where the ith order derivative of a quantity x with respect to k0 is denoted by
x
(
i
)
=
∂
i
⁢
x
∂
⁢
k
0
i
and the parameter d is given by
d
=
Dz
0
z
0
(
1
)
;
said profile function ƒ(r,λ) being related to said dopant concentrations Xi(r), i=1, 2, . . . , I by
f
⁡
(
r
,
k
0
)
=
∑
i
=
1
I
⁢
x
i
⁡
(
r
)
⁢
e
i
⁡
(
k
0
)
,
x
i
⁡
(
r
)
=
X
i
⁡
(
r
=
0
)
-
X
i
⁡
(
r
)
,
with ei(k0)=ziR(k0)−zS(k0) where ziR(k0) is the z due to a reference amount of dopant concentration for dopant l and zS is the z due to pure silica,
(h) providing the dopant concentration profiles as inputs to a deposition system that produces an optical fiber preform in which the concentration of each dopant in its core region corresponds to the inputted profiles.

139 more elements

A method of fabricating a near-optimum broadband multimode optical fiber comprising the steps of:

(a) determining desired performance characteristics of the fiber, including at least a core region and a cladding region surrounding said core region, said core region having a refractive index profile n(r,λ),
(b) determining desired structural characteristics of the fiber,
(c) determining the numerical aperture and bandwidth of the fiber,
(d) determining I different dopants that will be incorporated into the core region of the fiber, each of said dopants being characterized by a dopant concentration profile,
(e) setting up a numerical code to generate the dopant concentration profiles of each of said dopants by reducing the variation of z(r,λ) with respect to wavelength, where z(r,λ)n2(r,λ)k02, is radius, λ is wavelength, n is the refractive index of the core region, and
k
0
=
2
⁢
⁢
π
λ
is the wave number,
(f) setting u a numerical code to generate a profile function ƒ(r,λ) defined by ƒ(r,λ)=z0−z(r,λ), z0=z(r=0,λ) and ƒ(r=0,λ)=ƒ0=0, ƒ(r=a,λ)=ƒa=(NA·k0)2, where NA is the numerical aperture of the fiber and r=a is radius of said core region, said profile function satisfying equation (g) below,
(g) setting up a numerical code to generate
f
(
i
-
1
)
+
r
2
⁢
∂
f
(
i
-
1
)
∂
r
=
[
df
⁢
(
1
)
]
(
i
-
1
)
,
i
=
1
,
2
,
…
⁢
,
I
,
where the ith order derivative of a quantity x with respect to k0 is denoted by
x
(
i
)
=
∂
i
⁢
x
∂
⁢
k
0
i
and the parameter d is given by
d
=
Dz
0
z
0
(
1
)
;
said profile function ƒ(r,λ) being related to said dopant concentration profiles Xi(r), i=1, 2, . . . , I by
f
⁡
(
r
,
k
0
)
=
∑
i
=
1
I
⁢
x
i
⁡
(
r
)
⁢
e
i
⁡
(
k
0
)
,
x
i
⁡
(
r
)
=
X
i
⁡
(
r
=
0
)
-
X
i
⁡
(
r
)
,
(h) setting up a numerical code so that said dopant concentration profiles Xi(r) minimize the metric ξ given by:
ξ
=
∑
j
=
2
I
⁢
w
j
⁢

∑
i
=
1
I
⁢
[
r
⁢
dx
i
dr
]
⁢
e
i
(
j
-
1
)
⁡
(
k
0
)
-
∑
i
=
1
I
⁢
x
i
⁡
(
r
)
⁢
p
i
(
j
-
1
)
⁡
(
k
0
)

2
where ∥·∥t2 is the L2-norm, with ei(k0)=ziR(k0)−zS(k0) where ziR(k0) is the z due to a reference amount of dopant concentration for dopant i and is the z due to pure silica;
pi(k0)=2dei(1)−2ei and wj is the weight on the jth order derivative of said profile function ƒ(r,λ)
(i) setting up a numerical code so that said minimization is subject to the following equality criteria:
∑
i
=
1
I
⁢
[
r
⁢
dx
i
dr
]
⁢
e
i
(
0
)
⁡
(
k
0
)
=
∑
i
=
1
I
⁢
x
i
⁡
(
r
)
⁢
p
i
(
0
)
⁡
(
k
0
)
,
where xi(r) is pre-specified for some rε[0,α], k0 is the wave number, pi(0) and ei(0) are the zeroeth order derivatives or matrix elements e and p, and
(j) setting up a numerical code so that said minimization is subject to the following inequality constraints:
xi,min≦xi(r)≦xi,max, where xi,min=Xi(r=0)−Xi,max, xi,max=Xi(r=0), and
(k) providing the dopant concentration profiles as inputs to a deposition system that produces an optical fiber preform in which the concentration of each dopant in its core region corresponds to the inputted profiles.

260 more elements

Dependencies are inferred from the claim text.

Facts

Application: 14/725,226Filed 29 May 2015 · continuation in part
Priority: 31 Jan 2014
Published: US 2015/0253498 A110 Sep 2015
Granted: 31 Oct 2017
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

G02B 6/0288
With core or cladding having graded refractive index: multimode fibre, e.g. graded index core for compensating modal dispersion
G02B 6/0281
With core or cladding having graded refractive index: graded index region forming part of the central core segment, e.g. alpha profile,…
G02B 6/03627
Having 2 layers only: arranged - +
G02B 6/03633
Having 2 layers only: arranged - -

Family

Application61/934,223Us provisional application · filed 31 Jan 2014
Application62/004,376Us provisional application · filed 29 May 2014
PCT/US2015/013655Parent of this continuation-in-part · filed 30 Jan 2015
US 2015/0253498 A1Pre-grant publication · published 10 Sep 2015
US 9,804,325 B2This patent

From the US filing history. Foreign family members aren’t listed.

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Citations

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Abstract

Described is a technique for optimizing the design and manufacture of broadband MMFs. MMFs for use in CWDM applications are specifically described.

A broadband multimode optical fiber comprising:

a core region having a transverse cross-section and a longitudinal axis, said core region being configured for broadband operation at wavelengths λ within a predetermined wavelength range, Λ, and
a cladding region surrounding said core region,
said core and cladding regions being configured to support the propagation of optical radiation in said core region and along said axis simultaneously in a plurality of transverse modes,
said core region having a refractive index profile n(r,λ) and being co-doped with I different dopants having concentration profiles Xi(r), i=1, 2, . . . I, the concentrations and distributions of said dopants being radially varied within said transverse cross-section of said core region so that the refractive index of said core region is radially graded and so that variations in z(r,λ) with respect to wavelength are reduced, where
z(r,λ)n2(r,λ)k02,
r is radius, λ is the wavelength of said optical radiation, n is the refractive index of said core region,
k
0
=
2
⁢
π
λ
is the wave number, and wherein said concentrations and distribution of said dopants are also radially varied within said transverse cross-section of said core region so that said dopant concentration profiles are configured by the following criteria:
(a) a profile function ƒ(r,λ) is defined by ƒ(r,λ)=z0−z(r,λ), z0=z(r=0,λ),
(b) ƒ(r=0,λ)=ƒ0=0, ƒ(r=a,λ)=ƒa=(NA·k0)2, where NA is the numerical aperture of the fiber and equation (b) satisfies equation (c) below,
f
(
i
-
1
)
+
r
2
⁢
∂
f
(
i
-
1
)
∂
r
=
[
df
⁢
(
1
)
]
(
i
-
1
)
,
i
=
1
,
2
,
…
⁢
,
I
,
(
c
)
where the ith order derivative of a quantity x with respect to k0 is denoted by
x
(
i
)
=
∂
i
⁢
x
∂
⁢
k
0
i
and the parameter d is given by
d
=
Dz
0
z
0
(
1
)
;
and
(d) said profile function ƒ(r,λ) is related to said dopant concentration profiles Xi(r), t=1, 2, . . . , I by
f
⁡
(
r
,
k
0
)
=
∑
i
=
1
I
⁢
x
i
⁡
(
r
)
⁢
e
i
⁡
(
k
0
)
,
x
i
⁡
(
r
)
=
X
i
⁡
(
r
=
0
)
-
X
i
⁡
(
r
)
with ei(k0)=ziR(k0)−zS(k0) where ziR(k0) is the z due to a reference amount of dopant concentration for dopant i and zS is the z due to pure silica.

141 more elements

Facts

Application

14/725,226Filed 29 May 2015 · continuation in part

Priority

31 Jan 2014

Published

US 2015/0253498 A110 Sep 2015

Granted

31 Oct 2017

Term ends

Not estimatedThe source records don’t support an estimate.

Classification5 codes

G02B 6/0288
With core or cladding having graded refractive index: multimode fibre, e.g. graded index core for compensating modal dispersion
G02B 6/0281
With core or cladding having graded refractive index: graded index region forming part of the central core segment, e.g. alpha profile,…
G02B 6/03627
Having 2 layers only: arranged - +
G02B 6/03633
Having 2 layers only: arranged - -

Family

Application61/934,223Us provisional application · filed 31 Jan 2014

Application62/004,376Us provisional application · filed 29 May 2014

PCT/US2015/013655Parent of this continuation-in-part · filed 30 Jan 2015

US 2015/0253498 A1Pre-grant publication · published 10 Sep 2015

US 9,804,325 B2This patent

From the US filing history. Foreign family members aren’t listed.