# US 7,613,374 B2 · Optical fiber and optical-fiber transmission line

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- Number: US 7,613,374 B2
- Document ID: US7613374B2
- Status: Granted
- Kind: B2
- Application number: 12/133,782
- Filed: 2008-06-05
- Published: 2008-11-06
- Granted: 2009-11-03
- Earliest claimed: 2006-10-04
- Assignees: Furukawa Electric Co., Ltd.
- Inventors: Katsunori Imamura
- Web page: https://patentgrep.com/patent/US7613374B2

## CPC

- G02B 6/02009: {Large effective area or mode field radius, e.g. to reduce nonlinear effects in single mode fibres}
- G02B 6/02019: {Effective area greater than 90 square microns in the C band, i.e. 1530-1565 nm}
- G02B 6/02242: {having a dispersion slope <0.06 ps/km/nm2}
- G02B 6/03644: {arranged - + -}
- G02B 6/0288: {Multimode fibre, e.g. graded index core for compensating modal dispersion}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An optical fiber that transmits a signal light in a fundamental propagation mode has a cutoff wavelength longer than a wavelength of the signal light, a wavelength dispersion of the fundamental propagation mode of −5 ps/nm/km to −1 ps/nm/km at a wavelength of 1550 nanometers, an effective core area of the fundamental propagation mode larger than 45 μm2 at the wavelength of 1550 nanometers, and a dispersion slope of the fundamental propagation mode smaller than 0.03 ps/nm2/km at the wavelength of 1550 nanometers.

## Claims

### Claim 1

An optical fiber that transmits a signal light in a fundamental propagation mode, the optical fiber having
a cutoff wavelength longer than a wavelength of the signal light,
a wavelength dispersion of the fundamental propagation mode of −5 ps/nm/km to −1 ps/nm/km at a wavelength of 1550 nanometers,
an effective core area of the fundamental propagation mode larger than 45 μm2 at the wavelength of 1550 nanometers, and
a dispersion slope of the fundamental propagation mode smaller than 0.03 ps/nm2/km at the wavelength of 1550 nanometers, wherein the dispersion slope of the fundamental propagation mode is smaller than 0 ps/nm2/km at the wavelength of 1550 nanometers.

### Claim 2 (depends on 1)

The optical fiber according to claim 1, wherein the optical fiber comprises:
a center core region;
an inner core layer that is formed around the center core region and that has a refractive index lower than a refractive index of the center core region;
an outer core layer that is formed around the inner core layer and that has a refractive index higher than the refractive index of the inner core layer; and
a cladding layer that is formed around the outer core layer and that has a refractive index higher than the refractive index of the inner core layer and lower than the refractive index of the outer core layer, wherein
a relative refractive index difference of the center core region with respect to the cladding layer is equal to or smaller than 0.65%,
a ratio of an outer diameter of the inner core layer to a diameter of the center core region is equal to or larger than 1.3,
a ratio of an outer diameter of the outer core layer to the diameter of the center core region is equal to or larger than 2.0, and
the diameter of the center core region is equal to or larger than 5.9 micrometers.

### Claim 3 (depends on 1)

The optical fiber according to claim 1, wherein
the wavelength of the signal light is 1530 nanometers to 1570 nanometers, and
the cutoff wavelength is equal to or longer than 1600 nanometers.

### Claim 4 (depends on 1)

The optical fiber according to claim 1, wherein a bending loss of the fundamental propagation mode in a case of winding 16 turns with a winding diameter of 20 millimeters is equal to or smaller than 10 dB/m at the wavelength of 1550 nanometers.

### Claim 5

An optical fiber transmission line comprising:
an optical fiber that transmits a signal light in a fundamental propagation mode, the optical fiber having
a cutoff wavelength longer than a wavelength of the signal light,
a wavelength dispersion of the fundamental propagation mode of −5 to −1 ps/nm/km at a wavelength of 1550 nanometers,
an effective core area of the fundamental propagation mode larger than 45 μm2 at the wavelength of 1550 nanometers, and
a dispersion slope of the fundamental propagation mode smaller than 0.03 ps/nm2/km at the wavelength of 1550 nanometers, wherein the dispersion slope of the fundamental propagation mode is smaller than 0 ps/nm2/km at the wavelength of 1550 nanometers.

### Claim 6 (depends on 5)

The optical fiber transmission line according to claim 5, further comprising a single-mode optical fiber having a cutoff wavelength shorter than the wavelength of the signal light, the single-mode optical fiber being configured to be connected to the optical fiber, wherein
the optical fiber transmission line transmits the signal light from the single-mode optical fiber side.

### Claim 7 (depends on 6)

The optical fiber transmission line according to claim 6, wherein the single-mode optical fiber has a wavelength dispersion of −8 ps/nm/km to −1 ps/nm/km at the wavelength of 1550 nanometers, a dispersion slope larger than the dispersion slope of the fundamental propagation mode of the optical fiber at the wavelength of 1550 nanometers, and an effective core area larger than the effective core area of the fundamental propagation mode of the optical fiber at the wavelength of 1550 nanometers.