# US 10,557,986 B2 · Few mode optical fiber

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- Number: US 10,557,986 B2
- Document ID: US10557986B2
- Status: Granted
- Kind: B2
- Application number: 16/518,990
- Filed: 2019-07-23
- Published: 2019-11-14
- Granted: 2020-02-11
- Earliest claimed: 2017-11-28
- Assignees: Sterlite Technologies Limited
- Applicants: Sterlite Technologies Limited
- Inventors: Srinivas Reddy Munige; Anand Kumar Pandey
- Web page: https://patentgrep.com/patent/US10557986B2

## CPC

- G02B 6/0288: {Multimode fibre, e.g. graded index core for compensating modal dispersion}
- G02B 6/02023: {Based on higher order modes, i.e. propagating modes other than the LP01 or HE11 fundamental mode (mode converters G02B6/14)}
- G02B 6/02042: {Multicore optical fibres}
- G02B 6/02261: {Dispersion compensating fibres, i.e. for compensating positive dispersion of other fibres}
- G02B 6/0281: {Graded index region forming part of the central core segment, e.g. alpha profile, triangular, trapezoidal core (G02B6/0288, G02B6/0286 take precedence)}
- G02B 6/03683: {arranged - - + +}
- G02B 6/03688: {having 5 or more layers}
- H04J 14/04: Mode multiplex systems
- G02B 6/02019: {Effective area greater than 90 square microns in the C band, i.e. 1530-1565 nm}
- G02B 6/03605: {Highest refractive index not on central axis}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)

## Abstract

The present disclosure provides a few mode optical fiber (100). The few mode optical fiber (100) includes a core region (102). A core region (102) defined by a region around a central longitudinal axis (116) of the few mode optical fiber (100). In addition, the core region (102) has a first annular region (106) extended from central longitudinal axis (116) to radius r1, a second annular region (108) extended from radius r1 to radius r2, a third annular region (110) extended from radius r2 to radius r3, a fourth annular region (112) extended from radius r3 to radius r4 and a fifth annular region (114) extended from radius r4 to radius r5. Also, the few mode optical fiber (100) has a cladding defined by the sixth annular region (104) extended from radius r5 to radius r6.

## Claims

### Claim 1

A few mode optical fiber comprising:
a core region, defined by a region around a central longitudinal axis of the few mode optical fiber, wherein the core region further comprises:
a first annular region with an updopant and having a first refractive index, defined by the central longitudinal axis and a first radius,
a second annular region having a second refractive index, between the first radius and a second radius,
a third annular region with a downdopant and having a third refractive index, between the second radius and a third radius,
a fourth annular region having a fourth refractive index, wherein the fourth annular region is between the third radius and a fourth radius, and
a fifth annular region with an updopant and having a fifth refractive index, wherein the fifth annular region is between the fourth radius and a fifth radius; and
a cladding region that is a sixth annular region between the fifth radius and a sixth radius, having a sixth refractive index;
wherein the few mode optical fiber is operated in six modes including two degenerate Lp01 modes and four degenerate Lp11 modes.

### Claim 2 (depends on 1)

The few mode optical fiber of claim 1, wherein the first radius is in a range of 3.8 microns to 4.2 microns, the first refractive index is in a range of 0.42 to 0.70, the second radius is in a range of 4.8 microns to 5.2 microns, the second refractive index is approximately zero, the third radius is in a range of 8.2 microns to 8.7 microns, the third refractive index is in a range of 0.4 to 0.58, the fourth radius is in a range of 8.3 microns to 9.9 microns, the fourth refractive index is approximately zero, the fifth radius is in a range of 10.9 microns to 12.6 microns, the fifth refractive index is in a range of 0.41 to 0.62, the sixth radius is 62.5 microns, the sixth refractive index is approximately zero.

### Claim 3 (depends on 1)

The few mode optical fiber of claim 1, wherein the first annular region, the second annular region, the third region, the fourth region, the fifth region and the sixth annular region are concentrically arranged about the central longitudinal axis.

### Claim 4 (depends on 1)

The few mode optical fiber of claim 1, wherein the few mode optical fiber has a spatial overlap between the Lp01 mode and the Lp11 mode of less than 10−5.

### Claim 5 (depends on 4)

The few mode optical fiber of claim 4, wherein the first annular region has an alpha profile defined by a peak shaping parameter alpha, the peak shaping parameter alpha being in a range of 2.7 to 10.

### Claim 6 (depends on 1)

The few mode optical fiber of claim 1, wherein the few mode optical fiber having dimensions at least one or more of:
a mode field diameter in a range of 7.4 μm to 8.4 μm for the Lp01 mode at a wavelength of 1550 nm,
an effective area in a range of 43 μm2 to 55 μm2 for the Lp01 mode at a wavelength of 1550 nm, and
an effective area in a range of 368 μm2 to 570 μm2 for the Lp11 mode at a wavelength of 1550 nm.

### Claim 7 (depends on 1)

The few mode optical fiber of claim 1, wherein the few mode optical fiber having at least one or more properties comprising:
a theoretical cutoff wavelength in a range of 2280 nm to 2810 nm for the Lp11 mode,
a theoretical cutoff wavelength in a range of 1950 nm to 2500 nm for the Lp02 mode,
a differential group delay between the Lp01 mode and the Lp11 mode of less than 0.2 ps/km at a wavelength of 1550 nm,
a dispersion in a range of 4 Ps/nm/km to 16 Ps/nm/km for the Lp01 mode at a wavelength of 1460 nm,
a dispersion in a range of 0.3 ps/nm/km to 6 Ps/nm/km for the Lp11 mode at a wavelength of 1460 nm,
a dispersion in a range of 4.1 Ps/nm/km to 21 Ps/nm/km for the Lp01 mode at a wavelength of 1530 nm,
a dispersion in a range of 4.5 Ps/nm/km to 11 Ps/nm/km for the Lp11 mode at a wavelength of 1530 nm,
a dispersion in a range of 4 Ps/nm/km to 22 Ps/nm/km for the Lp01 mode at a wavelength of 1550 nm,
a dispersion in a range of 5.8 Ps/nm/km to 12 Ps/nm/km for the Lp11 mode at a wavelength of 1550 nm,
a dispersion in a range of 4.5 Ps/nm/km to 23 Ps/nm/km for the Lp01 mode at a wavelength of 1565 nm,
a dispersion in a range of 6.8 Ps/nm/km to 13 Ps/nm/km for the Lp11 mode at a wavelength of 1565 nm,
a dispersion in a range of 3.9 Ps/nm/km to 26 Ps/nm/km for the Lp01 mode at a wavelength of 1625 nm,
a dispersion in a range of 10 Ps/nm/km to 17 Ps/nm/km for the Lp11 mode at a wavelength of 1625 nm.

### Claim 8 (depends on 1)

The few mode optical fiber of claim 1, wherein the few mode optical fiber has a macrobending loss of less than 2.1 dB/turn for 16 mm bending radius at a wavelength of 1625 nm for the Lp11 mode.