Polarization maintaining optical fiber with improved polarization maintaining property

• US 6,788,865 B2
• Filed: 03/05/2001
• Issued: 09/07/2004
• Est. Priority Date: 03/03/2000
• Status: Expired due to Fees

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Kawanishi, Satoki, Okamoto, Katsunari
• Primary Examiner(s): Glick, Edward J.
• Assistant Examiner(s): Kao, Chih-Cheng Glen
• Application Number:
  US09/799,150
• Publication Number:
  US 20010026667A1
• Time in Patent Office: 1,282 Days
• Field of Search: 385/123, 385/124, 385/125, 385/127, 385/37, 385/11
• 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; and

a photonic crystal structure cladding provided in a surrounding of the core and having a diffraction grating with a lattice interval Λ

for realizing confinement of light within the core, the photonic crystal structure cladding being divided into four divided portions along a circumferential direction, all lattice holes in a first pair of divided portions that are facing each other along one direction having a larger lattice hole diameter d₂ than a smaller lattice hole diameter d₁ of all lattice holes in a second pair of divided portions that are facing each other along another direction orthogonal to the one direction, and in a graph in which a vertical axis represents d₁/Λ and

a horizontal axis represents d₂/Λ

, a ratio of the larger lattice hole diameter d₂ and the smaller lattice hole diameter d₁ takes a value within a region enclosed by four straight lines given by four equations;

2. 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 Λ

for realizing confinement of light within the core, the photonic crystal structure cladding being divided into four divided portions along a circumferential direction, only lattice holes closest to the core among lattice holes in a first pair of divided portions that are facing each other along one direction having a larger lattice hole diameter d₂ than a smaller lattice hole diameter d₁ of all other lattice holes among the lattice holes in the first pair of divided portions, all lattice holes in a second pair of divided portions that are facing each other along another direction orthogonal to the one direction having the smaller lattice hole diameter d₁, and in a graph in which a vertical axis represents d₁/Λ and

a horizontal axis represents d₂/Λ

, a ratio of the larger lattice hole diameter d₂ and the smaller lattice hole diameter d₁ takes a value within a region enclosed by four straight lines given by four equations;