Apparatus for fabricating optical fiber preform and method for fabricating low water peak fiber using the same

Abstract

Disclosed is a method for fabricating an optical fiber preform. The method includes: (a) growing a first soot preform on a starting member along a lengthwise direction of the starting member by a soot deposition; (b) dehydrating the first soot preform; (c) sintering the dehydrated first soot preform, to obtain a first glassed optical preform; and (d) elongating the first optical fiber preform by heating the first optical fiber with a heat source that excludes hydrogen, wherein the first glassed optical fiber is elongated by means of only a heat source that excludes the use of hydrogen.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a flowchart illustrating a conventional method for fabricating an optical fiber preform;

FIG. 2 is a flowchart illustrating a method for fabricating an optical fiber preform according to a preferred embodiment of the present invention;

FIG. 3 is a view illustrating a step for growing a first soot preform;

FIG. 4 is a view illustrating a step for dehydrating the first soot preform;

FIG. 5 is a view illustrating a step for sintering the first dehydrated soot preform;

FIGS. 6 to 8 are views illustrating steps for heating and elongating the first optical fiber preform;

FIG. 9 is a cross-sectional view showing the first elongated optical fiber;

FIG. 10 is a view illustrating a step for growing an outer clad;

FIG. 11 is a view illustrating steps for dehydrating and sintering a second soot preform;

FIG. 12 is a view showing the second optical fiber preform;

FIG. 13 is a view illustrating a step for drawing a low water peak optical fiber; and

FIG. 14 is a graph showing characteristics of the low water peak optical fiber.

Claims

1. A method for fabricating an optical fiber preform, comprising the steps of: (a) growing a first soot preform on a starting member along a lengthwise direction of the starting member by a soot deposition;(b) dehydrating the first soot preform;(c) sintering the dehydrated first soot preform, to obtain a first glassed optical preform; and(d) elongating the first glassed optical fiber preform by heating the first glassed optical fiber perform with a heat source that excludes hydrogen to obtain a first elongated glassed optical fiber preform.

2. The method of claim 1, further comprising the steps of: (e) growing an external clad on the first elongated glassed optical fiber preform by the soot deposition to obtain a second soot preform; and(f) dehydrating and sintering the second soot preform to obtain a second glassed optical fiber preform.

3. The method of claim 2, wherein step (f) is carried out in an atmosphere of a combination of chlorine gas and helium gas.

4. The method of claim 1, wherein the first elongated glassed optical fiber preform includes a core located at a center portion thereof, and an inner clad formed on an outer periphery of the core and having a low refractive index.

5. The method of claim 4, wherein a ratio D/d of a diameter D of the inner clad to a diameter d of the core with respect to the first elongated glassed optical fiber preform is less than 5.0.

6. The method of claim 4, wherein a ratio D/d of a diameter D of the inner clad to a diameter d of the core with respect to the first elongated glassed optical fiber preform is within a range of 4.1 to 4.5, inclusive.

7. A method for fabricating a low water peak optical fiber, comprising the steps of: (a) growing a first soot preform on a starting member along a lengthwise direction of the starting member by a soot deposition;(b) dehydrating the first soot preform;(c) sintering the dehydrated first soot preform, to obtain a first glassed optical preform;(d) elongating the first glassed optical fiber preform by heating the first glassed optical fiber with a heat source that excludes hydrogen;(e) growing an outer clad on the first elongated glassed optical fiber preform by the soot deposition, to obtain a second soot preform;(f) dehydrating and sintering the second soot preform to obtain a second glassed optical fiber preform; and(g) drawing a low water peak optical fiber by heating and softening an end portion of the second glassed optical fiber preform.

8. The method of claim 7, wherein step (f) is carried out in an atmosphere of a combination of chlorine gas and helium gas.

9. The method of claim 7, wherein the drawn low water peak optical fiber includes a core located at a center portion of the drawn low water peak optical fiber, an inner clad formed on an outer periphery of the core and having a refractive index less than that of the core, and an outer clad directly formed on a periphery of the inner clad.

10. The method as claimed in claim 9, wherein a ratio D/d of a diameter D of the inner clad to a diameter d of the core with respect to the drawn low water peak optical fiber is less than 5.0.

11. The method of claim 9, wherein a ratio D/d of a diameter D of the inner clad to a diameter d of the core with respect to the drawn low water peak optical fiber is within a range of 4.1 to 4.5, inclusive.