Polarization maintaining optical fiber with improved polarization maintaining property

• US 20010026667A1
• Filed: 03/05/2001
• Published: 10/04/2001
• Est. Priority Date: 03/03/2000
• Status: Active Grant

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Kawanishi, Satoki, Okamoto, Katsunari
• Granted Patent: US 6,788,865 B2
• Time in Patent Office: Days
• US Class Current: 385/125
• CPC Class Codes: G02B 6/02328 Hollow or gas filled core
• CPC Class Codes: G02B 6/02347 Longitudinal structures arranged to form a regular periodic lattice, e.g. triangular, square, honeycomb unit cell repeated throughout cladding
• CPC Class Codes: G02B 6/02357 Property of longitudinal structures or background material varies radially and/or azimuthally in the cladding, e.g. size, spacing, periodicity, shape, refractive index, graded index, quasiperiodic, quasicrystals
• CPC Class Codes: G02B 6/105 having optical polarisation effects

Abstract

A polarization maintaining optical fiber is formed by using a core in a cross sectional shape having different diameters along two orthogonal axes defined on a plane perpendicular to an optical axis, or a photonic crystal structure cladding having a diffraction grating with lattice intervals for realizing confinement of lights within the core which are different along two orthogonal axes defined on a plane perpendicular to an optical axis, or the photonic crystal structure cladding that is divided into four divided portions along a circumferential direction, where at least a part of lattice holes in a first pair of divided portions that are facing each other along one direction have a diameter larger than that of lattice holes in a second pair of divided portions that are facing each other along another direction orthogonal to the one direction.

Claims

1. A polarization maintaining optical fiber, comprising:

a core in a cross sectional shape having different diameters along two orthogonal axes defined on a plane perpendicular to an optical axis; and

a photonic crystal structure cladding which is provided in a surrounding of the core and having a diffraction grating with a lattice interval for realizing confinement of lights within the core.

2. The polarization maintaining optical fiber of

claim 1

, wherein the core has a rectangular cross sectional shape.

3. The polarization maintaining optical fiber of

claim 1

, wherein the core has an elliptic cross sectional shape.

4. The polarization maintaining optical fiber of

claim 1

, wherein the lattice interval is set approximately equal to a wavelength of lights to be propagated within the core.

5. The polarization maintaining optical fiber of

claim 1

, wherein the core is formed by a hollow hole.

6. The polarization maintaining optical fiber of

claim 1

, wherein the core is formed by a material having a lower refractive index than that of a material forming the photonic crystal structure cladding.

7. A polarization maintaining optical fiber, comprising:

a core in a form of a hollow hole; and

a photonic crystal structure cladding provided in a surrounding of the core and having a diffraction grating with lattice intervals for realizing confinement of lights within the core, the lattice intervals being different along two orthogonal axes defined on a plane perpendicular to an optical axis.

8. A polarization maintaining optical fiber, comprising:

a core; and

a photonic crystal structure cladding provided in a surrounding of the core and having a diffraction grating with lattice intervals for realizing confinement of lights within the core, the lattice intervals being different along two orthogonal axes defined on a plane perpendicular to an optical axis;

wherein the core is formed by a material having a lower refractive index than that of a material forming the photonic crystal structure cladding.

9. A polarization maintaining optical fiber, comprising:

a core; and

a photonic crystal structure cladding provided in a surrounding of the core and having a diffraction grating with a lattice interval for realizing confinement of lights within the core, the photonic crystal structure cladding being divided into four divided portions along a circumferential direction, at least a part of lattice holes in a first pair of divided portions that are facing each other along one direction having a larger lattice hole diameter than a smaller lattice hole diameter of lattice holes in a second pair of divided portions that are facing each other along another direction orthogonal to the one direction, and a ratio of the larger lattice hole diameter and the smaller lattice hole diameter satisfies a condition for realizing a single peak in a light intensity distribution in a vicinity of the core.

10. The polarization maintaining optical fiber of

claim 9

, wherein all the lattice holes in the first pair of the divided portions have the larger lattice hole diameter.

11. The polarization maintaining optical fiber of

claim 9

, wherein only lattice holes closest to the core among the lattice holes in the first pair of the divided portions have the larger lattice hole diameter.

12. A polarization maintaining optical fiber, comprising:

a core in a form of a hollow hole; and

a photonic crystal structure cladding provided in a surrounding of the core and having a diffraction grating with a lattice interval for realizing confinement of lights within the core, the photonic crystal structure cladding being divided into four divided portions along a circumferential direction, and at least a part of lattice holes in a first pair of divided portions that are facing each other along one direction having a larger lattice hole diameter than a smaller lattice hole diameter of lattice holes in a second pair of divided portions that are facing each other along another direction orthogonal to the one direction.

13. The polarization maintaining optical fiber of

claim 12

, wherein all the lattice holes in the first pair of the divided portions have the larger lattice hole diameter.

14. The polarization maintaining optical fiber of

claim 12

, wherein only lattice holes closest to the core among the lattice holes in the first pair of the divided portions have the larger lattice hole diameter.

15. A polarization maintaining optical fiber, comprising:

a core; and

a photonic crystal structure cladding provided in a surrounding of the core and having a diffraction grating with a lattice interval for realizing confinement of lights within the core, the photonic crystal structure cladding being divided into four divided portions along a circumferential direction, and at least a part of lattice holes in a first pair of divided portions that are facing each other along one direction having a larger lattice hole diameter than a smaller lattice hole diameter of lattice holes in a second pair of divided portions that are facing each other along another direction orthogonal to the one direction;

wherein the core is formed by a material having a lower refractive index than that of a material forming the photonic crystal structure cladding.

16. The polarization maintaining optical fiber of

claim 15

, wherein all the lattice holes in the first pair of the divided portions have the larger lattice hole diameter.

17. The polarization maintaining optical fiber of

claim 15

, wherein only lattice holes closest to the core among the lattice holes in the first pair of the divided portions have the larger lattice hole diameter.