# US 2025/0093575 A1 · Optical fiber

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- Number: US 2025/0093575 A1
- Document ID: US20250093575A1
- Status: Published application
- Kind: A1
- Application number: 18/294,124
- Filed: 2021-08-04
- Published: 2025-03-20
- Earliest claimed: 2021-08-04
- Assignees: Nippon Telegraph and Telephone Corporation
- Applicants: Nippon Telegraph and Telephone Corporation
- Inventors: Takashi MATSUI; Kazuhide NAKAJIMA; Nobutomo HANZAWA; Yuto SAGAE
- Web page: https://patentgrep.com/patent/US20250093575A1

## CPC

- G02B 6/02366: {Single ring of structures, e.g. "air clad"}
- G02B 6/032: with non solid core or cladding {(G02B6/02295 takes precedence)}
- G02B 6/036: core or cladding comprising multiple layers {(multicore optical fibres G02B6/02042; microstructured properties G02B6/02295; omniguide fibres G02B6/023)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An object of the present disclosure is to provide an optical fiber having a simple structure, as well as attaining removal of loss components generated in an electric field part oozing out to a core-clad interface or a clad region and reduction in scattering loss generated from an interface with the clad region. The present disclosure relates to an optical fiber including a core for propagating light, a cladding disposed around the core, an air layer between the core and the cladding, and two or more bridges for supporting the core in the air layer.

## Claims

### Claim 1

An optical fiber comprising:
a core for propagating light,
a cladding disposed around the core;
an air layer between the core and the cladding; and
two or more bridges for supporting the core in the air layer.

### Claim 2 (depends on 1)

The optical fiber according to claim 1, wherein a refractive index of the cladding is lower than a refractive index of the core.

### Claim 3 (depends on 2)

The optical fiber according to claim 2, wherein, given that the number of propagation modes is (n+1), the refractive index of the cladding is lower than an effective refractive index of an n-th order mode and higher than an effective refractive index of an (n+1)-th order mode.

### Claim 4 (depends on 1)

The optical fiber according to claim 1, wherein a thickness of the air layer is equal to or less than 1.6 μm.

### Claim 5 (depends on 1)

The optical fiber according to claim 1, wherein a relative refractive index difference Δ of the core to the cladding is as follows:
0.0748
a
-
1.962
<
Δ
<
0.18
a
-
1.941
[
Math
.
4
]
where a is a radius of the core.