Coupled multi-core optical fiber

Patent metadata

Field	Value
Publication number	US-10031283-B2
Application number	US-201715451922-A
Country	US
Kind code	B2
Filing date	Mar 7, 2017
Priority date	Mar 9, 2016
Publication date	Jul 24, 2018
Grant date	Jul 24, 2018

Abstract

The present embodiment relates to a CMCF including a structure to achieve more efficient reduction in transmission loss by suppressing decrease in concentration of alkali metal due to diffusion of alkali metal. In the CMCF including a plurality of cores, a power coupling coefficient h between adjacent cores is set to 1×10−3/m or more, to maintain an optical coupling state between the adjacent cores. In addition, alkali metal contributing to reduction in transmission loss is added to each of the cores such that a stress maximum value σ_max between adjacent cores has a negative value.

First claim

What is claimed is:

1. A coupled multi-core optical fiber comprising:
a plurality of cores extending from one end to the other end; and
a single cladding covering each of the cores, wherein
each of the plurality of cores includes alkali metal contributing to reduction in transmission loss,
a power coupling coefficient h between adjacent cores in the plurality of cores is 1×10 −3 /m or more, and
stress on a line segment connecting centers of the adjacent cores is compressive stress.

2. The coupled multi-core optical fiber according to claim 1 , wherein
a maximum value σ_ max of the stress on the line segment is −20 MPa or less.

3. The coupled multi-core optical fiber according to claim 1 , wherein
a distance Λ core between the adjacent cores is 35 μm or less.

4. The coupled multi-core optical fiber according to claim 1 , wherein
the cladding includes a diffusion center position in which concentration of the alkali metal has a local maximum value, and a distance Λ core-clad between the diffusion center position and a center position of a core adjacent to the diffusion center position among the plurality of cores is 45 μm or less.

5. The coupled multi-core optical fiber according to claim 1 , wherein
each of the plurality of cores is comprised of SiO 2 glass in which a concentration of GeO 2 molecules is set to be 0 wt % or more to 1 wt % or less,
fluorine is doped to the cladding, and
transmission loss of each of the plurality of cores at a wavelength of 1550 nm is 0.16 dB/km or less.

6. The coupled multi-core optical fiber according to claim 1 , wherein
germanium is doped to at least one of the plurality of cores, and
transmission loss of the core with added germanium is 0.18 dB/km or less at the wavelength of 1550 nm.

7. The coupled multi-core optical fiber according to claim 1 , wherein
average concentration of the alkali metal in each of the plurality of cores is 0.2 atom ppm or more and 50 atom ppm or less.

8. The coupled multi-core optical fiber according to claim 1 , wherein
average concentration of halogen elements in each of regions corresponding to the plurality of cores in a preform of the coupled multi-core optical fiber before drawing is 1000 atom ppm or more and 30000 atom ppm or less.

9. The coupled multi-core optical fiber according to claim 1 , wherein
concentration of the alkali metal in a surface of the cladding is 1 atom ppm or less.

Assignees

• Sumitomo Electric Industries

Inventors

• Nakanishi Tetsuya
• Hayashi Tetsuya

Classifications

• G02B6/06 Primary

  the relative position of the fibres being the same at both ends, e.g. for transporting images · CPC title

• G02B6/02014

  Effective area greater than 60 square microns in the C band, i.e. 1530-1565 nm · CPC title

• G02B6/02042 Primary

  Multicore optical fibres · CPC title

• G02B6/028

  with core or cladding having graded refractive index {(G02B6/02033, G02B6/02295 take precedence)} · CPC title

• C03C2201/50

  containing alkali metals · CPC title