Multi-core optical fiber, multi-core optical fiber cable, and optical fiber transmission system

Patent metadata

Field	Value
Publication number	US-9952382-B2
Application number	US-201615284713-A
Country	US
Kind code	B2
Filing date	Oct 4, 2016
Priority date	Oct 8, 2015
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

Abstract

The present embodiment relates to an MCF in which the strength of mode coupling or power coupling between adjacent cores included in one coupled-core group is set to an appropriate level to reduce a DGD. The MCF includes at least one coupled-core group. A core interval Λ between adjacent cores included in the coupled-core group is set such that a mode coupling coefficient between the adjacent cores at a wavelength of 1550 nm satisfies 2.6×10 0 [m −1 ] to 1.6×10 2 [m −1 ] or a power coupling coefficient between the adjacent cores at the wavelength of 1550 nm satisfies 1.3×10 −3 [m −1 ] to 8.1×10 0 [m −1 ].

First claim

What is claimed is:

1. A multi-core optical fiber comprising:
at least one coupled-core group constituted by a plurality of cores; and
a common cladding surrounding the coupled-core group,
wherein a core interval Λ between centers of adjacent cores among the plurality of cores is set such that a mode coupling coefficient between the adjacent cores at a wavelength of 1550 nm is 2.6×10 0 [m −1 ] to 1.6×10 2 [m −1 ] or a power coupling coefficient between the adjacent cores at the wavelength of 1550 nm is 1.3×10 −3 [m −1 ] to 8.1×10 0 [m −1 ].

2. The multi-core optical fiber according to claim 1 , wherein
the core interval Λ is set such that the mode coupling coefficient between the adjacent cores at the wavelength of 1550 nm is 2.1×10 1 [m −1 ] to 5.7×10 1 [m −1 ] or the power coupling coefficient between the adjacent cores at the wavelength of 1550 nm is 1.0×10 −1 [m −1 ] to 9.0×10 −1 [m −1 ].

3. An optical fiber transmission system comprising:
a transmission path including the multi-core optical fiber according to claim 1 ; and
a structure to compensate by MIMO signal processing for crosstalk between the spatial modes generated in the coupled-core group.

4. A multi-core optical fiber comprising:
at least one coupled-core group constituted by a plurality of cores; and
a common cladding surrounding the coupled-core group,
wherein the multi-core optical fiber has a core structure and a core arrangement satisfying following first to third conditions:
the first condition defined such that a core interval Λ [m] between centers of adjacent cores among the plurality of cores is set such that a mode coupling coefficient κ[m −1 ] between the adjacent cores at a wavelength of 1550 nm satisfies 1.6×10 2 [m −1 ′] or less;
the second condition defined such that κ/(βΛC avg ) or κ/(βΛC f ) becomes 0.1 or less in a wavelength range of 1530 to 1625 nm when C avg is set to 0.01 to 2 [m −1 ] or 0.1 to 1 [m −1 ]; and
the third condition defined κ becomes 2.6×10 0 [m −1 ] or more, or, κ/(βΛC avg ) or κ(βΛC f ) becomes 0.01 or more in the wavelength range of 1530 to 1625 nm,
where C avg [m −1 ] denotes an average value of a curvature of the multi-core optical fiber in a state in which the multi-core optical fiber is embedded in a cable, along a longitudinal direction of the multi-core optical fiber, C f [m −1 ] denotes a virtual curvature of the multi-core optical fiber in a straight fiber condition, and β [m −1 ] denotes an average value of propagation constants of the adjacent cores.

5. The multi-core optical fiber according to claim 4 , wherein
a transmission loss in full mode launch is 0.20 dB/km or less in a wavelength range of 1530 nm to 1565 nm or a wavelength range of 1460 nm to 1625 nm,
a mode average of a chromatic dispersion is 16 ps/(nm·km) or more,
in all of spatial modes, a bending loss when the multi-core optical fiber is wound on a mandrel having a diameter of 30 mm by one turn is 0.2 dB or less at a wavelength of 1550 nm,
in all of spatial modes, a bending loss when the multi-core optical fiber is wound on a mandrel having a diameter of 20 mm is 20 dB/m or less at the wavelength of 1550 nm,
in all of spatial modes, a bending loss when the multi-core optical fiber is wound on a mandrel having a radius of 30 mm by 100 turns is 0.5 dB or less at the wavelength of 1550 nm,
in the wavelength range of 1530 nm to 1565 nm or the wavelength range of 1460 nm to 1625 nm, an average value of a mode dependent loss is 0.01 dB/km 1/2 or less, and
in the wavelength range of 1530 nm to 1565 nm or the wavelength range of 1460 nm to 1625 nm, an average value of maximum values for respective wavelengths of a differential group delay between spatial modes is 10 ps/km 1/2 or less.

6. The multi-core optical fiber according to claim 4 , wherein
the common cladding includes: a common optical cladding that covers all of the plurality of cores; and a physical cladding that covers a periphery of the optical cladding,
an outer diameter of each of the plurality of cores is 6 to 15 μm, and
a difference of an index difference Λ of an average area of each of the plurality of cores and an index difference Λ of the optical cladding is 0.2 to 0.5%, an index difference Λ of the physical cladding is 0.0 to 1% higher than the index difference Λ of the optical cladding in a cross-section of the multi-core optical fiber orthogonal to the longitudinal direction, where all of the index differences Λ are expressed based on a refractive index of pure silica.

7. The multi-core optical fiber according to claim 6 , wherein
the coupled-core group is constituted by 2 to 15 cores,
an outer diameter of the physical cladding is 125±1 μm, and
the multi-core optical fiber satisfies a formula:
D J /a≥ 7.68×10 −2 ·X 2 −2.21×10 −1 ·X+ 3.15; or

D J /a≥ 7.57×10 −2 ·X 2 −2.25×10 −1 ·X+ 3.40,

where D J denotes a shortest distance of the physical cladding and a center of a proximity core closest to the physical cladding, D offset denotes a distance of a center of the optical cladding and the center of the proximity core, a character a denotes a radius of the proximity core, and X denotes log 10 (D offset /a).

8. A multi-core optical fiber cable in which a plurality of multi-core optical fibers are embedded, each of the plurality of multi-core optical fibers comprises:
at least one coupled-core group constituted by a plurality of cores; and
a common cladding surrounding the coupled-core group,
wherein the multi-core optical fiber has a core structure and a core arrangement satisfying following first to third conditions:
the first condition defined such that a core interval Λ [m] between centers of the adjacent cores among the plurality of cores is set such that a mode coupling coefficient κ [m −1 ] between the adjacent cores at a wavelength of 1550 nm satisfies 1.6×10 2 [m −1 ] or less;
the second condition defined such that κ/(βΛC avg ) or κ/(βΛC f ) becomes 0.1 or less in a wavelength range of 1530 to 1625 nm; and
the third condition defined such that κ becomes 2.6×10 0 [m −1 ] or more, or, κ/(βΛC avg ) or κ/(βΛC f ) becomes 0.01 or more in the wavelength range of 1530 to 1625 nm,
where C avg [m 1 ] denotes an average value of a curvature of the multi-core optical fiber in a state in which the multi-core optical fiber is embedded in the multi-core optical fiber cable, along a longitudinal direction of the multi-core optical fiber, C f [m −1 ] denotes a virtual curvature of the multi-core optical fiber in a straight fiber condition, and β [m −l ] denotes an average value of propagation constants of the adjacent cores.

9. The multi-core optical fiber cable according to claim 8 , wherein
the core structure and the core arrangement in each of the plurality of multi-core optical fibers are adjusted such that κ/(βΛC avg ) or κ/(βΛC f ) becomes 0.01 or more in the wavelength range of 1530 to 1625 nm.

10. The multi-core optical fiber cable according to claim 8 , wherein
C avg is 0.01 to 2 [m −1 ], in a state in which the multi-core optical fiber cable is not bent.

11. The multi-core optical fiber cable according to claim 8 , wherein
C avg is 0.1 [m −1 ] or more, 1 [m −1 ] or less, or 0.1 [m 1 ′] to 1 [m −1 ], in a state in which the multi-core optical fiber cable is not bent.

12. The multi-core optical fiber cable according to claim 8 , wherein
in each of the plurality of multi-core optical fibers, a transmission loss in full mode launch is 0.20 dB/km or less in a wavelength range of 1530 nm to 1565 nm or a wavelength range of 1460 nm to 1625 nm,
a mode average of a chromatic dispersion is 16 ps/(nm·km) or more,
in all of spatial modes, a

Assignees

• Sumitomo Electric Industries

Inventors

• Hayashi Tetsuya

Classifications

• G02B6/02042 Primary

  Multicore optical fibres · CPC title

• G02B6/02214

  tailored to obtain the desired dispersion, e.g. dispersion shifted, dispersion flattened · CPC title

• G02B6/02271

  Non-zero dispersion shifted fibres, i.e. having a small positive dispersion at 1550 nm, e.g. ITU-T G.655 dispersion between 1.0 to 10 ps/nm.km for avoiding nonlinear effects · CPC title

• G02B6/268

  for modal dispersion control, e.g. concatenation of light guides having different modal dispersion properties (graded index multimode fibres G02B6/0288; multimodal transmission systems H04B10/2581) · CPC title

• G02B6/4413

  Helical structure · CPC title