# US 9,435,943 B1 · Optical device

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- Number: US 9,435,943 B1
- Document ID: US9435943B1
- Status: Granted
- Kind: B1
- Application number: 15/045,645
- Filed: 2016-02-17
- Published: 2016-08-25
- Granted: 2016-09-06
- Earliest claimed: 2015-02-20
- Assignees: Fujikura Ltd.; National University Corporation Hokkaido University
- Applicants: Fujikura Ltd.; National University Corporation Hokkaido University
- Inventors: Katsuhiro Takenaga; Hitoshi Uemura; Kunimasa Saitoh
- Web page: https://patentgrep.com/patent/US9435943B1

## CPC

- G02B 6/02042: {Multicore optical fibres}
- G02B 6/02019: {Effective area greater than 90 square microns in the C band, i.e. 1530-1565 nm}
- G02B 6/02376: {Longitudinal variation along fibre axis direction, e.g. tapered holes}
- G02B 6/03644: {arranged - + -}
- G02B 6/368: {with pitch conversion between input and output plane, e.g. for increasing packing density}
- G02B 6/262: {Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements}
- G02B 6/3885: {Multicore or multichannel optical connectors, i.e. one single ferrule containing more than one fibre, e.g. ribbon type (optical ribbon cable G02B6/4403, G02B6/448)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

0.5377×r2−7.7≦V2/V1≦0.5377×r2−5.7, 3≦r2/r1≦5 are satisfied, where a radius of the inner core before tapered in diameter is defined as r1, a radius of the outer core before tapered in diameter is defined as r2, a refractive index volume formed of a product of a cross sectional area of the inner core and a relative refractive index difference of the inner core to the cladding before tapered in diameter is defined as V1, and a refractive index volume formed of a product of a cross sectional area of the outer core and a relative refractive index difference of the outer core to the cladding before tapered in diameter is defined as V2.

## Claims

### Claim 1

An optical device comprising:
a plurality of cores each including an inner core and an outer core surrounding an outer circumferential surface of the inner core, the outer core having a refractive index lower than a refractive index of the inner core; and
a cladding surrounding the outer circumferential surface of the core and having a refractive index lower than the refractive index of the outer core, wherein:
the optical device includes a tapered portion in which the each core is tapered in diameter from a first end to a second end of the core in a longitudinal direction and a pitch between the cores adjacent to each other is decreased;
when light propagates through the core tapered in diameter, a bending loss of an LP02 mode light beam and a bending loss of an LP21 light beam at a wavelength of 1.53 μm are 1.0 dB/m or greater at a radius of 140 mm, and a bending loss of an LP11 mode light beam at a wavelength of 1.625 μm is 0.5 dB/100 turns or less at a radius of 30 mm; and
0.5377×r2−7.7≦V2/V1≦0.5377×r2−5.7
3≦r2/r1≦5
are satisfied,
where a radius of the inner core before tapered in diameter is defined as r1, a radius of the outer core before tapered in diameter is defined as r2, a refractive index volume formed of a product of a cross sectional area of the inner core and a relative refractive index difference of the inner core to the cladding before tapered in diameter is defined as V1, and a refractive index volume formed of a product of a cross sectional area of the outer core and a relative refractive index difference of the outer core to the cladding before tapered in diameter is defined as V2.

### Claim 2 (depends on 1)

The optical device according to claim 1, wherein the radius r2 of the outer core before tapered in diameter is 15 μm or more.

### Claim 3 (depends on 1)

The optical device according to claim 1, wherein:
a length of the tapered portion is 4 mm or longer; and
a length of the core after tapered in diameter is 2 mm or longer.

### Claim 4 (depends on 3)

The optical device according to claim 3, wherein a length of the tapered portion is 6 mm or longer.

### Claim 5 (depends on 1)

The optical device according to claim 1, wherein
(V1′+V2′)/Vt≧1
is satisfied,
where a refractive index volume formed of a product of a cross sectional area of the inner core and a relative refractive index difference of the inner core to the cladding after tapered in diameter is defined as V1′, and a refractive index volume formed of a product of a cross sectional area of the outer core and a relative refractive index difference of the outer core to the cladding after tapered in diameter is defined as V2′, and
in a multicore fiber having a plurality of cores each to be coupled to each of the plurality of cores tapered in diameter, a refractive index volume formed of a product of a cross sectional area of the multicore fiber core and a relative refractive index difference of the multicore fiber core to a cladding surrounding an outer circumferential surface of the multicore fiber core is defined as Vt.

### Claim 6 (depends on 5)

The optical device according to claim 5, wherein a coupling loss of an LP01 mode light beam through the multicore fiber is equal to or greater than a coupling loss of an LP11 mode light beam through the multicore fiber.

### Claim 7 (depends on 2)

The optical device according to claim 2, wherein:
a length of the tapered portion is 4 mm or longer; and
a length of the core after tapered in diameter is 2 mm or longer.

### Claim 8 (depends on 7)

The optical device according to claim 7, wherein a length of the tapered portion is 6 mm or longer.

### Claim 9 (depends on 2)

The optical device according to claim 2, wherein
(V1′+V2′)/Vt≧1
is satisfied,
where a refractive index volume formed of a product of a cross sectional area of the inner core and a relative refractive index difference of the inner core to the cladding after tapered in diameter is defined as V1′, and a refractive index volume formed of a product of a cross sectional area of the outer core and a relative refractive index difference of the outer core to the cladding after tapered in diameter is defined as V2′, and
in a multicore fiber having a plurality of cores each to be coupled to each of the plurality of cores tapered in diameter, a refractive index volume formed of a product of a cross sectional area of the multicore fiber core and a relative refractive index difference of the multicore fiber core to a cladding surrounding an outer circumferential surface of the multicore fiber core is defined as Vt.

### Claim 10 (depends on 9)

The optical device according to claim 9, wherein a coupling loss of an LP01 mode light beam through the multicore fiber is equal to or greater than a coupling loss of an LP11 mode light beam through the multicore fiber.

### Claim 11 (depends on 3)

The optical device according to claim 3, wherein
(V1′+V2′)/Vt≧1
is satisfied,
where a refractive index volume formed of a product of a cross sectional area of the inner core and a relative refractive index difference of the inner core to the cladding after tapered in diameter is defined as V1′, and a refractive index volume formed of a product of a cross sectional area of the outer core and a relative refractive index difference of the outer core to the cladding after tapered in diameter is defined as V2′, and
in a multicore fiber having a plurality of cores each to be coupled to each of the plurality of cores tapered in diameter, a refractive index volume formed of a product of a cross sectional area of the multicore fiber core and a relative refractive index difference of the multicore fiber core to a cladding surrounding an outer circumferential surface of the multicore fiber core is defined as Vt.

### Claim 12 (depends on 11)

The optical device according to claim 11, wherein a coupling loss of an LP01 mode light beam through the multicore fiber is equal to or greater than a coupling loss of an LP11 mode light beam through the multicore fiber.

### Claim 13 (depends on 4)

The optical device according to claim 4, wherein
(V1′+V2′)/Vt≧1
is satisfied,
where a refractive index volume formed of a product of a cross sectional area of the inner core and a relative refractive index difference of the inner core to the cladding after tapered in diameter is defined as V1′, and a refractive index volume formed of a product of a cross sectional area of the outer core and a relative refractive index difference of the outer core to the cladding after tapered in diameter is defined as V2′, and
in a multicore fiber having a plurality of cores each to be coupled to each of the plurality of cores tapered in diameter, a refractive index volume formed of a product of a cross sectional area of the multicore fiber core and a relative refractive index difference of the multicore fiber core to a cladding surrounding an outer circumferential surface of the multicore fiber core is defined as Vt.

### Claim 14 (depends on 13)

The optical device according to claim 13, wherein a coupling loss of an LP01 mode light beam through the multicore fiber is equal to or greater than a coupling loss of an LP11 mode light beam through the multicore fiber.