Multi-core fiber

Patent metadata

Field	Value
Publication number	US-9588284-B2
Application number	US-201615062530-A
Country	US
Kind code	B2
Filing date	Mar 7, 2016
Priority date	Mar 7, 2014
Publication date	Mar 7, 2017
Grant date	Mar 7, 2017

Abstract

In a C band and an L band, the effective refractive indices of light propagating through the cores 11 and 21 adjacent to each other are different from each other such that a magnitude of crosstalk of light of a highest-order LP mode commonly propagating through the cores 11 and 21 adjacent to each other between the cores 11 and 21 adjacent to each other becomes a peak at a bending diameter smaller than a diameter of 100 mm, and the core has a higher refractive index in a center portion than in an outer circumferential portion such that a differential mode group delay of the cores 11 and 12 is 700 picoseconds/km or less.

First claim

The invention claimed is:

1. A multi-core fiber comprising:
nine or more core elements each including a core that propagates light of at least up to a second-order LP mode in a C band and an L band, an inner cladding layer that surrounds an outer circumferential face of the core and has a refractive index lower than a refractive index of the core, and a trench layer that surrounds an outer circumferential face of the inner cladding layer and has a refractive index lower than the refractive index of the inner cladding layer; and
an outer cladding that surrounds outer circumferential faces of the trench layers and has a refractive index higher than the refractive index of the trench layer and lower than the refractive index of the core,
wherein effective refractive indices of light propagating through cores adjacent to each other are different from each other such that a magnitude of crosstalk of light of a highest-order LP mode commonly propagating through the cores adjacent to each other between the cores adjacent to each other becomes a peak at a bending diameter smaller than a diameter of 100 mm, and
wherein the core has a higher refractive index in an area including a center axis than in an area disposed on an outer circumferential side such that a differential mode group delay of the core is 700 picoseconds/km or less.

2. The multi-core fiber according to claim 1 , wherein an outer diameter of the outer cladding is 125 μm or more and 230 μm or less.

3. The multi-core fiber according to claim 1 , wherein a difference between effective areas of light of a same LP mode propagating through the cores is 20 μm 2 or less.

4. The multi-core fiber according to claim 1 , wherein a bending loss of light of a highest-order LP mode of light having a longest wavelength propagating through each of the cores is 0.5 dB or less in a case where the cores are rolled 100 turns with a diameter of 60 mm.

5. The multi-core fiber according to claim 1 , wherein the magnitude of the crosstalk of the light of the highest-order LP mode commonly propagating through the cores adjacent to each other between the cores adjacent to each other is −30 dB/100 km or less.

6. The multi-core fiber according to claim 1 ,
wherein the core includes an inner area that includes a center axis and an outer area that surrounds an outer circumferential face of the inner area without any gap and is surrounded by the inner cladding layer without any gap, and
wherein a refractive index of the inner area is higher than a refractive index of the outer area.

7. The multi-core fiber according to claim 1 , wherein the refractive index of the core decreases from a center axis toward an outer circumferential side, and a change rate of the refractive index increases toward the outer circumferential side.

8. The multi-core fiber according to claim 1 , wherein the cores are arranged in an annular shape.

9. The multi-core fiber according to claim 8 ,
wherein the number of the cores is even, and
wherein the two types of the cores having mutually-different effective refractive indices of the propagating light are arranged to be adjacent to each other.

10. The multi-core fiber according to claim 1 , wherein the cores are arranged in a square lattice shape.

11. The multi-core fiber according to claim 10 ,
wherein the number of the core elements is 12, and
wherein the cores are respectively arranged on lattice points of a predetermined tetragonal lattice and lattice points of a tetragonal lattice adjacent to the predetermined tetragonal lattice.

12. The multi-core fiber according to claim 10 , wherein the two types of the cores having mutually-different effective refractive indices of propagating light are arranged to be adjacent to each other.

13. The multi-core fiber according to claim 1 , wherein a wavelength band of light propagating through the cores is a C band.

14. The multi-core fiber according to claim 1 ,
wherein an outer diameter of the outer cladding is 125 μm or more and 230 μm or less,
wherein the refractive index of the core decreases from a center axis toward an outer circumferential side, and a change rate of the refractive index increases toward the outer circumferential side,
wherein a difference between effective areas of light of a same LP mode propagating through the cores is 10 μm 2 or less,
wherein a cutoff wavelength of light of an LP21 mode of each of the cores is 1530 nm or less,
wherein a bending loss of light of the highest-order LP mode of light having a longest wavelength propagating through each of the cores is 0.5 dB or less in a case where each of the cores is rolled 100 turns with a diameter of 60 mm,
wherein a differential mode group delay of the cores is 100 picoseconds/km or less, and
wherein the magnitude of the crosstalk of light of the highest-order LP mode commonly propagating through the cores adjacent to each other between the cores adjacent to each other is −30 dB/100 km or less.

15. The multi-core fiber according to claim 14 ,
wherein the number of the core elements is 12, and the core elements are arranged in a tetragonal lattice shape, and
wherein the cores are respectively arranged on lattice points of a predetermined tetragonal lattice and lattice points of a tetragonal lattice adjacent to the predetermined tetragonal lattice.

Assignees

• Fujikura Ltd
• Nat Univ Corp Hokkaido Univ

Inventors

• Sasaki Yusuke
• Takenaga Katsuhiro
• AMMA Yoshimichi
• Saitoh Kunimasa

Classifications

• G02B6/02219

  Characterised by the wavelength dispersion properties in the silica low loss window around 1550 nm, i.e. S, C, L and U bands from 1460-1675 nm · CPC title

• G02B6/0288

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

• G02B6/028

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

• G02B6/036

  core or cladding comprising multiple layers {(multicore optical fibres G02B6/02042; microstructured properties G02B6/02295; omniguide fibres G02B6/023)} · CPC title

• G02B6/02042 Primary

  Multicore optical fibres · CPC title