Optical Fiber and Optical Transmission Medium

• US 20080124036A1
• Filed: 09/13/2006
• Published: 05/29/2008
• Est. Priority Date: 10/11/2005
• Status: Active Grant

• Current Assignee: Furukawa Electric Company Limited
• Original Assignee: Furukawa Electric Company Limited
• Inventors: Mimura, Yu, Miyabe, Ryo
• Granted Patent: US 7,529,453 B2
• Time in Patent Office: Days
• US Class Current: 385/125
• CPC Class Codes: G02B 6/02333 Core having higher refractive index than cladding, e.g. solid core, effective index guiding
• 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 6/02361 Longitudinal structures forming multiple layers around the core, e.g. arranged in multiple rings with each ring having longitudinal elements at substantially the same radial distance from the core, having rotational symmetry about the fibre axis
• CPC Class Codes: G02B 6/02376 Longitudinal variation along fibre axis direction, e.g. tapered holes
• CPC Class Codes: G02B 6/02385 Comprising liquid, e.g. fluid filled holes
• CPC Class Codes: G02B 6/03622 having 2 layers only
• CPC Class Codes: G02B 6/03638 having 3 layers only

Abstract

The present invention can easily realize an optical fiber and an optical transmission line that can propagate a light in a single mode while lowering a macro-bending loss against a small-diameter bending. An optical fiber 1 according to the present invention includes a first cladding region 3 having a refractive index lower than a refractive index of a core region 2 on outer circumference of the core region 2. Sub-medium regions 5a to 5f, 6a to 6f are arranged in multilayer in the first cladding region 3, which have a refractive index lower than a refractive index of a main-medium region of the first cladding region 3. The sub-medium regions 5a to 5f having a circular shape with a lateral cross section of a diameter d1 is arranged in an inner cladding area 3a of the first cladding region 3, and the sub-medium regions 6a to 6f having a circular shape with a lateral cross section of a diameter d2 (>d1) is arranged in an outer cladding area 3b of the first cladding region 3.

Claims

1-19. -19. (canceled)

20. An optical fiber including a core region and a cladding region, wherein

the cladding region includes a first cladding region on an outer circumference of the core region, the first cladding region consisting of a main-medium region and a sub-medium region, a refractive index of the sub-medium region being lower than a refractive index of the main-medium region,

the sub-medium region includes a plurality of inner sub-medium regions arranged along the outer circumference of the core region and a plurality of outer sub-medium regions arranged on an outer side of the inner sub-medium regions along the outer circumference of the core region, and

a lateral cross section of the outer sub-medium regions is larger than a lateral cross section of the inner sub-medium regions.

21. The optical fiber according to claim 20, wherein a center of each lateral cross section of the outer sub-medium regions is located in a region sandwiched by lines formed by connecting a center of each lateral cross section of the inner sub-medium regions adjacent to each other and a center of a lateral cross section of the core region.

22. The optical fiber according to claim 20, wherein the center of each lateral cross section of the inner sub-medium regions and the center of each lateral cross section of the outer sub-medium regions are respectively located in a concentric manner centering on the center of the core region.

23. The optical fiber according to claim 20, wherein

the inner sub-medium regions are respectively arranged at six folds rotationally symmetric centering on the core region, and

the outer sub-medium regions are respectively arranged at six folds rotationally symmetric centering on the core region.

24. The optical fiber according to claim 20, wherein

a hole is formed at each position where the sub-medium region is arranged, along a center axis of the core region, and

the sub-medium region is composed of any one of a gaseous substance, a liquid, and a solid substance that fills inside of the hole.

25. The optical fiber according to claim 20, wherein

the cladding region further includes a second cladding region on an outer circumference of the first cladding region, the second cladding region being homogeneous, and

a relative refractive index difference between the core region and the second cladding region is equal to or larger than 0.3% and equal to or smaller than 0.4%.

26. The optical fiber according to claim 25, wherein a medium of the second cladding region is a pure silica glass.

27. The optical fiber according to claim 25, wherein a medium of the second cladding region is a fluorine-doped silica glass.

28. The optical fiber according to claim 25, wherein a medium of the second cladding region is same as a medium that forms the main-medium region of the first cladding region.

29. The optical fiber according to claim 20, wherein the core region is formed by a silica glass doped with at least one of germanium and phosphor.

30. The optical fiber according to claim 20, wherein a light having a wavelength of equal to or longer than 1500 nanometers propagates through the optical fiber in a single mode.

31. The optical fiber according to claim 20, wherein a light having a wavelength of equal to or longer than 1280 nanometers propagates through the optical fiber in a single mode.

32. The optical fiber according to claim 20, wherein

a mode field diameter at a wavelength of 1550 nanometers is equal to or larger than 6 micrometers and equal to or smaller than 11 micrometers, and

a macro-bending loss with a curvature radius of 7.5 millimeters at the wavelength of 1550 nanometers is equal to or less than 0.1 decibel per meter.

33. The optical fiber according to claim 20, wherein a macro-bending loss with a curvature radius of 5.0 millimeters at a wavelength of 1550 nanometers is equal to or less than 0.1 decibel per meter.

34. An optical transmission medium comprising:

an optical fiber in a state in which the optical fiber is bent with a curvature radius of equal to or larger than 3 millimeters and equal to or smaller than 60 millimeters, the optical fiber including a core region and a cladding region, wherein

the cladding region includes a first cladding region on an outer circumference of the core region, the first cladding region consisting of a main-medium region and a sub-medium region, a refractive index of the sub-medium region being lower than a refractive index of the main-medium region,

the sub-medium region includes a plurality of inner sub-medium regions arranged along the outer circumference of the core region and a plurality of outer sub-medium regions arranged on an outer side of the inner sub-medium regions along the outer circumference of the core region, and

a lateral cross section of the outer sub-medium regions is larger than a lateral cross section of the inner sub-medium regions.

35. The optical transmission medium according to claim 34, wherein the optical fiber is in a state in which the optical fiber is rolled in a coil with the curvature radius of equal to or larger than 3 millimeters and equal to or smaller than 60 millimeters.

36. The optical transmission medium according to claim 34, wherein the optical fiber is connected to an other optical fiber in a state in which an end of the sub-medium region formed in the cladding region along the center axis of the core region is blocked.

37. The optical transmission medium according to claim 36, wherein the end of the sub-medium region is blocked by filling a predetermined filling agent in the end of the sub-medium region.

38. The optical transmission medium according to claim 36, wherein the end of the sub-medium region is blocked by collapsing the end of the sub-medium region.