Single mode optical fiber, method of manufacturing the same, and apparatus for manufacturing the same

• US 20030086670A1
• Filed: 05/28/2002
• Published: 05/08/2003
• Est. Priority Date: 07/30/2001
• Status: Active Grant

• Current Assignee: Furukawa Electric Company Limited
• Original Assignee: Furukawa Electric Company Limited
• Inventors: Inoue, Yoshihiro, Kurusu, Kazuhiko, Moridaira, Hideya
• Granted Patent: US 6,954,572 B2
• Time in Patent Office: Days
• US Class Current: 385/123
• CPC Class Codes: C03B 2201/12 doped with fluorine C03B2201/14 takes precedence
• CPC Class Codes: C03B 2201/20 doped with non-metals other than boron or fluorine
• CPC Class Codes: C03B 2201/31 doped with germanium
• CPC Class Codes: C03B 2203/24 Single mode [SM or monomode]
• CPC Class Codes: C03B 2205/42 Drawing at high speed, i.e. > 10 m/s
• CPC Class Codes: C03B 2205/45 Monotoring or regulating the preform neck-down region with respect to position or shape
• CPC Class Codes: C03B 2205/47 Shaping the preform draw bulb before or during drawing
• CPC Class Codes: C03B 2205/56 Annealing or re-heating the drawn fibre prior to coating
• CPC Class Codes: C03B 2205/83 using gas
• CPC Class Codes: C03B 2205/90 Manipulating the gas flow through the furnace other than by use of upper or lower seals, e.g. by modification of the core tube shape or by using baffles
• CPC Class Codes: C03B 37/01446 Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering C03B37/01853 takes precedence
• CPC Class Codes: C03B 37/027 Fibres composed of different sorts of glass, e.g. glass optical fibresC03B37/0253, C03B37/028 take precedence
• CPC Class Codes: C03B 37/02718 Thermal treatment of the fibre during the drawing process, e.g. cooling coating C03C25/10
• CPC Class Codes: C03B 37/02772 shaping the preform lower end or bulb, e.g. pre-gobbing, controlling draw bulb shape, or preform draw start-up procedures
• CPC Class Codes: C03B 37/029 Furnaces therefor
• CPC Class Codes: C03C 13/04 Fibre optics, e.g. core and clad fibre compositions light guides G02B6/00
• CPC Class Codes: G02B 6/03611 Highest index adjacent to central axis region, e.g. annular core, coaxial ring, centreline depression affecting waveguiding
• CPC Class Codes: G02B 6/03627 arranged - +
• CPC Class Codes: G02B 6/03633 arranged - -
• CPC Class Codes: G02B 6/03644 arranged - + -
• CPC Class Codes: G02B 6/03666 : arranged - + - +
• CPC Class Codes: Y02P 40/57 : Improving the yield, e-g- reduction of reject rates

Abstract

In a single mode optical fiber formed of a silica-based glass and including a glass part having a central core and a cladding region, the density of non bridging oxygen hole center in the glass part is not higher than 1.0×10¹⁴ spins/g in terms of the spin density measured by an electron spin resonance method.

Claims

1. A single mode optical fiber formed of a silica-based glass and including a glass part having a central core and a cladding region, wherein density of non bridging oxygen hole centers in said glass part as a value of spin density measured by a electron spin resonance method is not higher than 1.0×

10¹⁴ spins/g.

2. The single mode optical fiber according to claim 1, wherein density of paramagnetic defect Si (D)-E′

in said glass part is not lower than 1.0×

10¹² spins/g in terms of value of spin density measured by an electron spin resonance method.

3. The single mode optical fiber according to claim 1, wherein light emission intensity in a wavelength region in a vicinity of 650 nm in a cross section of said glass part, which is measured by a cathode luminescence method, is distributed such that the intensity is highest in an annular region in the outside and vicinity of an outer circumferential portion of said central core and is moderately decreased toward the outside of said central core.

4. The single mode optical fiber according to claim 1, wherein germanium is added to said central core.

5. The single mode optical fiber according to claim 1, wherein fluorine is added to the annular region positioned adjacent to said central core of said glass part.

6. The single mode optical fiber according to claim 1, wherein the chlorine concentration in said cladding region is higher than that in the central core.

7. A method of manufacturing the single mode optical fiber defined in claim 1, comprising diffusing deuterium into said glass part so as to decrease the spin density of non bridging oxygen hole center and to increase the spin density of peroxy radical.

8. A single mode optical fiber formed of a silica-based glass and including a glass part having a central core and a cladding region, wherein at least one element selected from the group consisting of Ge and F is added to said glass part, said glass part has an outer diameter of about 125 μ

m, and the density of the non bridging oxygen hole centers included in the MFD region of said glass part is lower than the density of non bridging oxygen hole center included in said cladding region positioned outside the MFD region.

9. The single mode optical fiber according to claim 8, wherein density of non bridging oxygen hole center contained in a region having a radius of 25 μ

m from the center of said glass part is not higher than 1×

10¹³ spins/g in terms of spin density measured by an electron spin resonance method.

10. The single mode optical fiber according to claim 8, wherein chlorine concentration in said cladding region is not lower than 1,000 ppm.

11. The single mode optical fiber according to claim 8, wherein density of paramagnetic defect Si-E′

contained in said glass part is not lower than 5×

10¹³ spins/g in terms of spin density measured by an electron spin resonance method.

12. The single mode optical fiber according to claim 8, wherein increase in loss other than the increase in loss caused by hydrogen molecules diffused into the glass part after exposure to hydrogen gas of 1 atm. under room temperature is not larger than 0.1 dB/km in a wavelength range of 1.38 mm to 1.42 μ

m.

13. A single mode optical fiber formed of a silica-based glass and including a glass part having a central core and a cladding region, wherein at least one element selected from the group consisting of Ge and F is added to said glass part, said glass part has an outer diameter of about 125 μ

m, and fictive temperature obtained by a ratio of a defect line denoting a three-membered ring structure of the glass to a defect line denoting a four-membered ring structure, which is obtained by measuring deviation between Rayleigh scattering line and Raman scattering line, is not higher than 1,200°

C.

14. The single mode optical fiber according to claim 13, wherein the increase in loss other than the increase in loss caused by hydrogen molecules diffused into glass part after exposure to hydrogen gas of 1 atm. under room temperature is not larger than 0.05 dB/km in the wavelength range of 1.38 μ

m to 1.42 μ

m.

15. A method of manufacturing a single mode optical fiber formed of a silica-based glass and including a glass part having a central core and a cladding region, wherein at least one element selected from the group consisting of Ge and F is added to said glass part, and said glass part has an outer diameter of about 125 μ

m, comprising;

heating an optical fiber preform so as to melt said optical fiber preform;

fiber drawing an optical fiber from said molten optical fiber preform; and

continuously cooling said drawn optical fiber starting with a meniscus portion in which diameter is decreased from 90% of the preform diameter to 5% of the preform diameter to a portion where the drawn optical fiber has a temperature of 1,200°

C. at a cooling rate of 1,000 to 3,000°

C./sec.

16. The method of manufacturing a single mode optical fiber according to claim 15, wherein said optical fiber preform is a silica-based glass soot obtained by a flame hydrolysis method, and said soot is sintered under a condition substantially free from oxygen.

17. An apparatus for manufacturing an optical fiber, comprising:

a heating furnace for heating an optical fiber preform, said heating furnace including a first heater; and

a mechanism for fiber drawing an optical fiber from said optical fiber preform that is melted within said heating furnace,

wherein a lower cylinder having a length L₁ meeting the inequality given below is arranged in contact with a bottom end side of said heating furnace, and the optical fiber is continuously cooled within said lower cylinder such that a meniscus portion of the drawn preform, in which a diameter of the preform melted within the heating furnace is decreased from 90% of the preform diameter to 5% of the preform diameter, has a length not smaller than “

A×

5”

where A represents the diameter (mm) of the preform;

L₁ (mm)>

B×

B/300

wherein B represents drawing speed (m/min) of the optical fiber.

18. The apparatus for manufacturing an optical fiber according to claim 17, wherein a second heater for heating the optical fiber withdrawn from within said heating furnace is arranged in said lower cylinder, and a length L₂ of said second heater meets an inequality given below:

L₂ (mm)>

C×

B/200

wherein B represents drawing speed (m/min) of the optical fiber, and C represents diameter (mm) of the optical fiber preform.

19. The apparatus for manufacturing an optical fiber according to claim 17, wherein distance L₃ between a top end side of said first heater and a top end side of said heating furnace and distance L₄ between a bottom end side of said first heater and the bottom end side of said heating furnace meet inequalities given below:

L₃>

C×

B/200 L₄>

C×

B/200

wherein B represents drawing speed (m/min) of the optical fiber, and C represents diameter (mm) of the optical fiber preform.