Multimode optical fiber

Patent metadata

Field	Value
Publication number	US-2016291246-A1
Application number	US-201514609689-A
Country	US
Kind code	A1
Filing date	Jan 30, 2015
Priority date	Jan 30, 2015
Publication date	Oct 6, 2016
Grant date	—

Abstract

An embodiment of the invention relates to a GI-MMF with a structure for achieving widening of bandwidth in a wider wavelength range and improving manufacturing easiness of a refractive index profile in a core. In an example of the GI-MMF, a whole region of the core is doped with Ge and a part of the core is doped with P. Namely, the Ge-doped region coincides with the whole region of the core and the Ge-doped region is comprised of a partially P-doped region doped with Ge and P; and a P-undoped region doped with Ge but not intentionally doped with P.

First claim

What is claimed is:

1 . A multimode optical fiber comprising:
a core extending along a predetermined axis and doped with germanium and phosphorus; and a cladding provided on an outer peripheral surface of the core, wherein the core has a Graded-Index type refractive index profile formed by doping with the germanium and the phosphorus, wherein in a cross section of the core perpendicular to the predetermined axis, a germanium-doped region doped with the germanium coincides with a whole region of the cross section of the core, and wherein in the cross section of the core, the germanium-doped region is comprised of a partially phosphorus-doped region in which a relative refractive index difference with respect to the cladding, resulting from the doping with the phosphorus, is controlled; and a phosphorus-undoped region in which a doping amount of the phosphorus is set to be not more than 5% of a maximum doping amount of the phosphorus in the partially phosphorus-doped region.

2 . The multimode optical fiber according to claim 1 , wherein in the germanium-doped region, the phosphorus-undoped region is arranged so as to surround the whole of the partially phosphorus-doped region.

3 . The multimode optical fiber according to claim 2 , wherein the partially phosphorus-doped region and the phosphorus-undoped region are arranged in contact with each other, and
wherein when r represents a distance from a center of the core to a boundary between the partially phosphorus-doped region and the phosphorus-undoped region and Δn(P) does a maximum relative refractive index difference resulting from the doping with the phosphorus in the partially phosphorus-doped region with respect to the cladding, the distance r is set so that an evaluation function defined by Expression (1) below becomes maximum.

min


(

B
0.850

4.700

,

B
0.875

4.200

,

B
0.900

3.600

,

B
0.925

3.300

,

B
0.950

3.100

)

(
1
)

where B 0.850 is an EMB (GHz·km) being one of transmission bandwidths at the wavelength 0.850 μm, with variation of the distance r and the maximum relative refractive index difference Δn(P), the numeral 4.700 a target EMB (GHz·km) at the wavelength 0.850 μm, B 0.875 an EMB (GHz·km) at the wavelength 0.875 μm, with variation of the distance r and the maximum relative refractive index difference Δn(P), the numeral 4.200 a target EMB (GHz·km) at the wavelength 0.875 μm, B 0.900 an EMB (GHz·km) at the wavelength 0.900 μm, with variation of the distance r and the maximum relative refractive index difference Δn(P), the numeral 3.600 a target EMB (GHz·km) at the wavelength 0.900 μm, B 0.925 an EMB (GHz·km) at the wavelength 0.925 μm, with variation of the distance r and the maximum relative refractive index difference Δn(P), the numeral 3.300 a target EMB (GHz·km) at the wavelength 0.925 μm, B 0.950 an EMB (GHz·km) at the wavelength 0.950 μm, with variation of the distance r and the maximum relative refractive index difference Δn(P), and the numeral 3.100 a target EMB (GHz·km) at the wavelength 0.950 μm.

4 . The multimode optical fiber according to claim 1 , wherein the partially phosphorus-doped region is doped with a constant doping amount of the phosphorus along a radial direction of the core.

5 . A multimode optical fiber comprising:
a core extending along a predetermined axis and doped with germanium and fluorine; and a cladding provided on an outer peripheral surface of the core, wherein the core has a Graded-Index type refractive index profile formed by doping with the germanium and the fluorine, wherein in a cross section of the core perpendicular to the predetermined axis, a germanium-doped region doped with the germanium coincides with a whole region of the cross section of the core, and wherein in the cross section of the core, the germanium-doped region is comprised of a partially fluorine-doped region in which a relative refractive index difference with respect to the cladding, resulting from the doping with the fluorine, is controlled; and a fluorine-undoped region in which a doping amount of the fluorine is set to be not more than 5% of a maximum doping amount of the fluorine in the partially fluorine-doped region.

6 . The multimode optical fiber according to claim 5 , wherein in the germanium-doped region, the partially fluorine-doped region is arranged so as to surround the whole of the fluorine-undoped region.

7 . The multimode optical fiber according to claim 6 , wherein the partially fluorine-doped region and the fluorine-undoped region are arranged in contact with each other, and
wherein when r represents a distance from a center of the core to a boundary between the partially fluorine-doped region and the fluorine-undoped region and Δn(F) does a minimum relative refractive index difference resulting from the doping with the fluorine in the partially fluorine-doped region with respect to the cladding, the distance r is set so that an evaluation function defined by Expression (2) below becomes maximum.

min


(

B
0.850

4.700

,

B
0.875

4.200

,

B
0.900

3.600

,

B
0.925

3.300

,

Assignees

• Sumitomo Electric Industries

Inventors

• Shiozaki Manabu
• Yonezawa Kazuhiro
• Enomoto Tadashi

Classifications

• C03C2201/31

  containing germanium · CPC title

• C03C13/046

  Multicomponent glass compositions · CPC title

• C03C2201/28

  containing phosphorus · CPC title

• G02B6/0288 Primary

  Multimode fibre, e.g. graded index core for compensating modal dispersion · CPC title

• G02B6/0365

  arranged - - + · CPC title