Optical fiber

• US 7,532,797 B2
• Filed: 08/22/2006
• Issued: 05/12/2009
• Est. Priority Date: 08/22/2005
• Status: Active Grant

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Hirano, Masaaki
• Primary Examiner(s): Doan; Jennifer
• Application Number:
  US11/791,702
• Publication Number:
  US 20080166097A1
• Time in Patent Office: 994 Days
• Field of Search: 385123-127
• US Class Current: 385/123
• CPC Class Codes: G02B 6/02214 tailored to obtain the desired dispersion, e.g. dispersion shifted, dispersion flattened
• CPC Class Codes: G02B 6/02261 Dispersion compensating fibres, i.e. for compensating positive dispersion of other fibres
• CPC Class Codes: G02B 6/0228 Characterised by the wavelength dispersion slope properties around 1550 nm G02B6/02228 takes precedence
• CPC Class Codes: G02B 6/03627 arranged - +
• CPC Class Codes: G02B 6/03644 arranged - + -

Abstract

The present invention relates to an optical fiber for light pulse expansion in which the ratio (β₃/β₂) of the third derivative β₃ to the second derivative β₂ is negative, the absolute value thereof is large, and the absolute value of the second derivative β₂ is also large. Such an optical fiber comprises at least a central core portion having a maximum refractive index N₁ and an outer diameter 2a, a depressed portion, provided on the outer periphery of the central core portion, having a minimum refractive index N₂ and an outer diameter 2b, and a cladding portion, provided on the outer periphery of the depressed portion, having a maximum refractive index N₃. The respective maximum refractive indices of the central core portion, the depressed portion and the cladding portion satisfy the relationship “N₁>N₃>N₂”.

Claims

1. An optical fiber comprising at least:

a central core portion having a maximum refractive index N₁ and an outer diameter 2a;

a depressed portion, provided on an outer periphery of said central core portion, having a minimum refractive index N₂ and an outer diameter 2b; and

a cladding portion, provided on an outer periphery of said depressed portion, having a maximum refractive index N₃,

wherein said respective maximum refractive indices of said central core portion, said depressed portion and said cladding portion satisfy the following relationship;

N₁>

N₃>

N₂,

wherein a relative refractive index difference Δ

₁ of said central core portion with respect to said cladding portion is larger than 1.0%, and a relative refractive index difference Δ

₂ of said depressed portion with respect to said cladding portion is smaller than −

0.3%, and

wherein, at a wavelength of 1.05 μ

m, the second derivative β

₂ of the propagation constant β

with respect to frequency ω

is positive, the third derivative β

₃ of the propagation constant β

with respect to frequency ω

is negative, and the ratio (β

₃/β

₂) of the third derivative β

₃ to the second derivative β

₂ is −

0.002 ps or less.

2. An optical fiber according to claim 1, wherein a ratio Ra(=2a/12b) of the outer diameter 2a of said central core portion to the outer diameter 2b of said depressed portion is 0.2 or more but less than 0.6.

3. An optical fiber according to claim 1, wherein the relative refractive index difference Δ

₁ of said central core portion is 1.7% or more.

4. An optical fiber according to claim 1, wherein the relative refractive index difference Δ

₂ of said depressed portion is −

0.5% or less.

5. An optical fiber according to claim 1, wherein the outer diameter 2a of said central core portion is 1.4 μ

m or more but 4.0 μ

m or less.

6. An optical fiber according to claim 1, having a bending loss of 100 dB/m or less at the wavelength of 1.05 μ

m, while being wound in a diameter of 40 mm.

7. An optical fiber according to claim 1, further comprising a ring portion, provided between said depressed portion and said cladding portion, having a maximum refractive index N₄ and an outer diameter 2c,

wherein the respective maximum refractive indices of said central core portion, said depressed portion, said ring portion and said cladding portion satisfy the following relationship:

N₁>

N₄>

N₃>

N₂.

8. An optical fiber coil including an optical fiber according to claim 1, while being winded into a coil shape.

9. An optical fiber coil according to claim 8, wherein the minimum wound diameter of said optical fiber is 120 mm or less.