# US 8,787,719 B2 · Bend insensitive fiber

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- Number: US 8,787,719 B2
- Document ID: US8787719B2
- Status: Granted
- Kind: B2
- Application number: 13/652,656
- Filed: 2012-10-16
- Published: 2013-04-18
- Granted: 2014-07-22
- Earliest claimed: 2011-10-17
- Assignees: Samsung Electronics Co., Ltd.
- Applicants: Yeong-Seop Lee; Mun-Hyun Do; Si-Ho Song; Myung-Hwan Pyo; Dae-Hwan Oh; Won-Sun Lee; Dae-Seung Moon; Tae-Hyung Lee; Tae-Hun Kim
- Inventors: Yeong-Seop Lee; Mun-Hyun Do; Si-Ho Song; Myung-Hwan Pyo; Dae-Hwan Oh; Won-Sun Lee; Dae-Seung Moon; Tae-Hyung Lee; Tae-Hun Kim
- Web page: https://patentgrep.com/patent/US8787719B2

## CPC

- C03B 37/01413: {Reactant delivery systems (C03B37/01807 takes precedence; devices therefor in general B01D1/00, B01J4/00)}
- C03B 37/01807: {Reactant delivery systems, e.g. reactant deposition burners}
- C03B 2201/12: doped with fluorine (C03B2201/14 takes precedence)
- C03B 2203/23: Double or multiple optical cladding profiles
- C03B: MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES

## Abstract

Provided is an extreme bending insensitive optical fiber. The optical fiber includes a core comprising a maximum refractive index difference Δn1 in the optical fiber, an inner layer comprising a refractive index difference Δn2 that is smaller than the maximum refractive index of the core and decreases in a direction away from the core, the inner layer being positioned outside the core, and a trench layer comprising an inner-circumference refractive index difference Δn3 that is smaller than the refractive index difference of the inner layer and an outer-circumference refractive index difference Δn4 that is a minimum refractive index difference in the optical fiber.

## Claims

### Claim 1

An optical fiber comprising:
a core comprising a maximum refractive index difference Δn1 in the optical fiber;
an inner layer comprising a refractive index difference Δn2 that is smaller than the maximum refractive index of the core and decreases in a direction away from the core, the inner layer being positioned outside the core; and
a trench layer comprising an inner-circumference refractive index difference Δn3 that is smaller than the refractive index difference of the inner layer and an outer-circumference refractive index difference Δn4 that is a minimum refractive index difference in the optical fiber, the trench layer being positioned outside the inner layer,
wherein a refractive index difference of the trench layer gradually decreases from an inner surface to an outer surface of the trench layer, a ratio (Δn3/Δn4) of the inner-circumference refractive index difference Δn3 to the outer-circumference refractive index difference Δn4 is larger than 0.6 and smaller than 1, a ratio (a+b)/b of a radius ‘a’ of the core and a thickness ‘b’ of the inner layer is less than 2.8, and the optical fiber comprises a cutoff wavelength of 1260 nm or less, a bending loss α1 of 1.0 dB or less in bending by a radius of 10 mm or less at a wavelength of 1550 nm, and a ratio (α2/α1) of a bending loss α2 at 1625 nm to the bending loss α1 at 1550 nm being less than 2.7.

### Claim 2 (depends on 1)

The optical fiber of claim 1, wherein the maximum refractive index difference of the core is less than 0.48Δ% and the outer-circumference refractive index difference of the trench layer is less than −0.21Δ%.

### Claim 3 (depends on 1)

The optical fiber of claim 1, further comprising an outer layer that has a refractive index difference which is larger than the refractive index difference of the trench layer and smaller than the maximum refractive index of the core, the outer layer being positioned outside the trench layer.

### Claim 4 (depends on 1)

The optical fiber of claim 1, wherein the refractive index difference Δn2 of the inner layer is in a range of −0.07Δ% to 0.1Δ%.

### Claim 5 (depends on 1)

The optical fiber of claim 1, wherein the radius of the core is in a range of 3.0 μm to 7.0 μm.

### Claim 6 (depends on 1)

The optical fiber of claim 1, wherein the thickness of the inner layer is in a range of 4.5 μm to 17.5 μm.

### Claim 7 (depends on 1)

The optical fiber of claim 1, wherein the optical fiber has a bending loss of 1.0 dB/turn or less in bending by a radius of 2.5 mm at a wavelength of 1550 nm.

### Claim 8 (depends on 1)

The optical fiber of claim 1, wherein the ratio (α2/α1) of the bending loss α2 at 1625 nm to the bending loss α1 at 1550 nm is 2.5 or less.

### Claim 9 (depends on 1)

The optical fiber of claim 1, wherein the optical fiber has a zero-dispersion wavelength in a range of 1300 nm to 1324 nm and an inclination of the zero-dispersion wavelength is less than 0.092 ps/(nm2·km).

### Claim 10 (depends on 1)

The optical fiber of claim 1, wherein the inner layer comprises:
a first inner sub layer that has a refractive index difference which decreases in a direction away from the core; and
a second inner sub layer that has a constant refractive index difference.

### Claim 11 (depends on 1)

The optical fiber of claim 1, wherein the trench layer is formed by a modified chemical vapor deposition (MCVD) process, and the trench layer is formed by depositing SiO2 and an F-dopant on a substrate tube and increasing a flow rate of the F-dopant.

### Claim 12 (depends on 1)

The optical fiber of claim 1, wherein the trench layer is formed by an outside vapor deposition process, and the trench layer is formed by sequentially reducing a density of a soot forming the trench layer.