Optical fiber and slanted fiber grating

Patent metadata

Field	Value
Publication number	US-10908353-B2
Application number	US-201816192833-A
Country	US
Kind code	B2
Filing date	Nov 16, 2018
Priority date	Nov 17, 2017
Publication date	Feb 2, 2021
Grant date	Feb 2, 2021

Abstract

An optical fiber is made of silica-based glass and includes a core, a first cladding that surrounds the core and that has a refractive index lower than a refractive index of the core; and a second cladding that surrounds the first cladding and that has a refractive index lower than the refractive index of the core and higher than the refractive index of the first cladding. At least a part of the first cladding contains a photosensitive material whose refractive index increases by irradiation with light having a specific wavelength. A difference Δn between a refractive index of a portion of the first cladding, the portion being nearest to the core, and the refractive index of the core is in a range of 0.25% to 0.30%. The radius ra of the core is larger than 4.3 μm and smaller than or equal to 5.0 μm.

First claim

What is claimed is:

1. A slanted fiber grating including a Bragg grating in at least a partial region in an optical fiber, the optical fiber made of silica-based glass and comprising:
a core that includes a central axis of the optical fiber and that has a radius ra that is larger than 4.3 μm and smaller than or equal to 5.0 μm;
a first cladding that is in contact with the core, that surrounds the core, that has an outer radius rb, and that has a refractive index lower than a refractive index of the core; and
a second cladding that is in contact with the first cladding, that surrounds the first cladding, and that has a refractive index lower than the refractive index of the core and higher than the refractive index of the first cladding,
wherein at least a part of the first cladding contains a photosensitive material whose refractive index increases by irradiation with light,
wherein, at the radius ra, a derivative of a refractive index with respect to a distance from the central axis along a straight line perpendicular to the central axis is minimum,
wherein, in a graph in which the straight line perpendicular to the central axis is a horizontal axis and the refractive index is a vertical axis, a difference between a maximum value of the refractive index of the core and a value that an extension of a straight line connecting a refractive index at a radius of (ra+1 μm) and a refractive index at a radius of (rb−1 μm) takes at the radius ra is in a range of 0.25% to 0.30% relative to a refractive index of 1.444024, and
wherein the photosensitive material is GeO 2 .

2. The slanted fiber grating according to claim 1 ,
wherein the first cladding and the second cladding of the optical fiber each contain fluorine.

3. The slanted fiber grating according to claim 1 ,
wherein at the radius rb of the first cladding of the optical fiber, a derivative of a refractive index with respect to a distance from the central axis of the optical fiber along a straight line perpendicular to the central axis is maximum.

4. The slanted fiber grating according to claim 3 ,
wherein the first cladding and the second cladding of the optical fiber each contain fluorine.

5. The slanted fiber grating according to claim 1 ,
wherein the Bragg grating is formed in at least a partial region of the first cladding of the optical fiber in a direction of the central axis and is inclined relative to the central axis.

6. A slanted fiber grating including a Bragg grating in at least a partial region in an optical fiber, the optical fiber made of silica-based glass and comprising:
a core that includes a central axis of the optical fiber and that has a radius ra that is larger than 4.3 μm and smaller than or equal to 5.0 μm;
a first cladding that is in contact with the core, that surrounds the core, that has an outer radius rb, and that has a refractive index lower than a refractive index of the core; and
a second cladding that is in contact with the first cladding, that surrounds the first cladding, and that has a refractive index lower than the refractive index of the core and higher than the refractive index of the first cladding,
wherein at least a part of the first cladding contains a photosensitive material whose refractive index increases by irradiation with light,
wherein, at the radius ra, a derivative of a refractive index with respect to a distance from the central axis along a straight line perpendicular to the central axis is minimum,
wherein, in a graph in which the straight line perpendicular to the central axis is a horizontal axis and the refractive index is a vertical axis, a difference between a maximum value of the refractive index of the core and a value that an extension of a straight line connecting a refractive index at a radius of (ra+1 μm) and a refractive index at a radius of (rb−1 μm) takes at the radius ra is in a range of 0.20% to 0.30% relative to a refractive index of 1.444024, and
wherein the photosensitive material is GeO 2 .

Assignees

• Sumitomo Electric Industries

Inventors

• Nagano Shigehiro
• Shiozaki Manabu
• Kinugasa Jun
• Hasegawa Takemi

Classifications

• G02B6/0283

  Graded index region external to the central core segment, e.g. sloping layer or triangular or trapezoidal layer (G02B6/0288, G02B6/0286 take precedence) · CPC title

• G02B6/03627 Primary

  arranged - + · CPC title

• G02B6/02085 Primary

  characterised by the grating profile, e.g. chirped, apodised, tilted, helical · CPC title

• G02B6/02114

  characterised by enhanced photosensitivity characteristics of the fibre, e.g. hydrogen loading, heat treatment (treatment of glass fibres by ion diffusion, implantation, radiation, C03C25/60, C03C25/62) · CPC title