# US 2019/0169064 A1 · Optical fiber preform production method and optical fiber production method

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 2019/0169064 A1
- Document ID: US20190169064A1
- Status: Published application
- Kind: A1
- Application number: 16/322,182
- Filed: 2017-08-01
- Published: 2019-06-06
- Earliest claimed: 2016-08-02
- Assignees: Sumitomo Electric Industries, Ltd.
- Applicants: Sumitomo Electric Industries, Ltd.
- Inventors: Tadashi ENOMOTO; Kazuhiro YONEZAWA
- Web page: https://patentgrep.com/patent/US20190169064A1

## CPC

- C03B 37/01807: {Reactant delivery systems, e.g. reactant deposition burners}
- C03B 37/01861: {Means for changing or stabilising the diameter or form of tubes or rods}
- C03B 19/06: by sintering, {e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by sintering slurries or dispersions not undergoing a liquid phase reaction}
- C03B 37/018: by glass deposition on a glass substrate, e.g. by {inside-, modified-, plasma- or plasma modified-} chemical vapour deposition {[ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod} (C03B37/016 takes precedence; surface treatment of glass by coating with glass C03C17/02)
- G02B 6/02: Optical fibres with cladding {with or without a coating}
- G02B 6/028: with core or cladding having graded refractive index {(G02B6/02033, G02B6/02295 take precedence)}
- C03B 2201/08: doped with boron or fluorine or other refractive index decreasing dopant
- C03B 2201/28: doped with phosphorus
- C03B 2201/31: doped with germanium
- C03B 2203/26: Parabolic or graded index [GRIN] core profile
- G02B 6/0288: {Multimode fibre, e.g. graded index core for compensating modal dispersion}
- C03B: MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

The present embodiment relates to a production method for matching a shape of a refractive index profile of a core preform with an ideal curve with high precision and in a short time. Prior to a glass synthesis step of stacking a plurality of glass layers including a refractive index adjusting agent of a predetermined amount on an inner peripheral surface or on an outer peripheral surface of a glass deposition substrate, glass synthesis actual-result data is created from production condition data of a glass preform produced in the past and refractive index profile data of a core preform obtained from the glass preform. In each glass synthesis section where the glass synthesis step is executed, a doping amount of the refractive index adjusting agent is adjusted on the basis of the glass synthesis actual-result data.

## Claims

### Claim 1

An optical fiber preform production method for producing a core preform which extends along a center axis and constitutes a part of an optical fiber preform and in which a refractive index profile defined along a radial direction on a cross-section orthogonal to the center axis is adjusted to a predetermined shape, the method comprising
a glass synthesis step of sequentially stacking glass particles synthesized while a doping amount of a refractive index adjusting agent M is adjusted on an inner peripheral surface or an outer peripheral surface of a glass deposition substrate extending along a direction matched with the center axis to thereby produce, to produce a glass preform as the glass preform to be the core preform, the glass preform having a cross-section in which a plurality of glass layers are concentrically arranged so as to be matched with the cross-section of the core preform and surround the center axis,
wherein the optical fiber preform production method further comprises a pretreatment step executed prior to the glass synthesis step, the pretreatment step of:
for one of a cross-section of an i-th (=1 to m) core preform sample among m (an integer of 2 or more) core preform samples produced in the past and the number of the glass layers constituting an i-th glass preform sample having become the i-th core preform sample, dividing an arbitrarily set adjustment region into n (an integer of 2 or more) sections along the radial direction and for the other, dividing a region corresponding to the adjustment region along the radial direction to correspond to the n division sections on one-to-one basis;
creating glass synthesis actual-result data including actual measurement data of a relative refractive index difference of a k-th (=1 to n) division section in the i-th core preform sample as refractive index profile data and including doping amount data of the refractive index adjusting agent M doped to the k-th division section in the i-th glass preform sample as production condition data;
calculating a correlation between a deviation of the actual measurement data of the relative refractive index difference with respect to a target value and the doping amount data of the refractive index adjusting agent M from glass synthesis actual-result data of the k-th division section of each of the m core preform samples; and
calculating a theoretical doping amount of the refractive index adjusting agent M in which an absolute value of the deviation is minimized from the correlation in the k-th division section of each of the m core preform samples, and
wherein the glass synthesis step sequentially forms one or more glass layers belonging to a k-th glass synthesis section corresponding to the k-th division section of each of the m core preform samples on the inner peripheral surface or the outer peripheral surface of the glass deposition substrate, in a state in which the doping amount of the refractive index adjusting agent M to be supplied at the time of synthesizing the glass particles is adjusted to the theoretical doping amount.

### Claim 2 (depends on 1)

The optical fiber preform production method according to claim 1, wherein an outer periphery radius rk of the k-th division section to be an index representing the k-th division section in the i-th core preform sample and a k-th glass synthesis section lk in the i-th glass preform sample satisfy a relation of the following expression (1) by a predetermined function f,
{
r
k
=
f

(
l
k
)
l
k
=
f
-
1

(
r
k
)
(
1
)
where the doping amount of the refractive index adjusting agent M in the k-th division section of the i-th core preform sample to be the glass synthesis actual-result data of the i-th core preform sample is set to M(rk)i and a deviation of the relative refractive index difference in the k-th division section of the i-th core preform sample is set to ε(rk)i, a theoretical doping amount M(rk)opt of the refractive index adjusting agent M in the k-th division section of the core preform to be produced is given by the following expression (2),
M

(
r
k
)
opt
=
(
∑
i
=
1
m

M

(
r
k
)
i
2
)

(
∑
i
=
1
m

ɛ

(
r
k
)
i
)
-
(
∑
i
=
1
m

M

(
r
k
)
i
)

(
∑
i
=
1
m

M

(
r
k
)
i
·
ɛ

(
r
k
)
i
)
(
∑
i
=
1
m

M

(
r
k
)
i
)

(
∑
i
=
1
m

ɛ

(
r
k
)
i
)
-
m

(
∑
i
=
1
m

M

(
r
k
)
i
·
ɛ

(
r
k
)
i
)
(
2
)
and a theoretical a doping amount M(lk)opt of the refractive index adjusting agent M in the k-th glass synthesis section lk to be produced in the glass preform to be the core preform is given by the theoretical doping amount M(rk)opt of the refractive index adjusting agent M in rk associated with lk by the expression (1).

### Claim 3 (depends on 1)

The optical fiber preform production method according to claim 1, wherein the refractive index adjusting agent M includes one kind of dopant.

### Claim 4 (depends on 1)

The optical fiber preform production method according to claim 1, wherein the refractive index adjusting agent M includes germanium.

### Claim 5 (depends on 1)

The optical fiber preform production method according to claim 1, wherein the refractive index adjusting agent M includes one kind of first dopant and one or more kinds of second dopants, and
the glass synthesis step adjusts a doping amount of the first dopant for each glass synthesis section to be formed, in a state in which doping conditions of the second dopants are fixed during a period where n glass synthesis sections are formed.

### Claim 6 (depends on 5)

The optical fiber preform production method according to claim 5, wherein the refractive index adjusting agent M includes two or more kinds of dopants selected from germanium, phosphorus, fluorine, and boron.

### Claim 7 (depends on 6)

The optical fiber preform production method according to claim 6, wherein the first dopant includes germanium.

### Claim 8 (depends on 1)

The optical fiber preform production method according to claim 1, further comprising: a sintering step of sintering the glass preform to cause the glass preform produced by the glass synthesis step to be transparent.

### Claim 9 (depends on 1)

The optical fiber preform production method according to claim 1, wherein the glass deposition substrate includes a hollow glass tube, and
the glass synthesis step sequentially stacks the plurality of glass layers on an inner peripheral surface of the glass tube.

### Claim 10 (depends on 1)

An optical fiber production method comprising: preparing the optical fiber preform including the core preform produced by the optical fiber preform production method according to claim 1; and
producing an optical fiber which includes a core extending along the center axis by drawing one end of the optical fiber preform while heating the one end and a cladding covering an outer peripheral surface of the core along the center axis and in which a deviation of a refractive index profile in the core of the optical fiber from a target refractive index profile is 0.002% or less as a relative refractive index difference with respect to a refractive index of pure silica glass.

### Claim 11 (depends on 1)

An optical fiber production method comprising: preparing the optical fiber preform produced by the optical fiber preform production method according to claim 1 and including a core preform having a refractive index profile according to an α-profile along the radial direction orthogonal to the center axis; and
producing a multimode optical fiber which includes a core extending along the center axis by drawing one end of the optical fiber preform while heating the one end and a cladding covering an outer peripheral surface of the core along the center axis and in which an α value defining a shape of the α-profile is in a range of 1.9 to 2.3 and an effective bandwidth EMB(λ) at an arbitrary wavelength λ(nm) included in a range of 800 to 1000 nm is −20·λ+700 MHz·km or more.