Multiple LP mode fiber designs for mode division multiplexing

Patent metadata

Field	Value
Publication number	US-8948559-B2
Application number	US-201313838981-A
Country	US
Kind code	B2
Filing date	Mar 15, 2013
Priority date	Sep 5, 2012
Publication date	Feb 3, 2015
Grant date	Feb 3, 2015

Abstract

The specification describes modified step index and GRaded INdex (GRIN) fibers with low core relative delta (near 0.8%) which have desirable properties for transmission. These lower delta fibers have lower attenuation losses due to reduced Rayleigh scattering, which is desirable to improve performance in multiple mode multiplexing. The fiber designs include optimized raised triangle profiles, and depressed cladding profiles, to support two and four LP modes.

First claim

The invention claimed is:

1. An optical fiber, comprising:
a core and a cladding surrounding the core,
wherein the core and cladding have a refractive index profile that is structured to support propagation of a plurality of desired signal-carrying modes, while suppressing undesired modes,
wherein the core comprises a portion extending from the center of the core, n core , to radius a, in which the refractive index decreases linearly from n core to point a,
wherein the cladding comprises a down-doped cladding region abutting or adjacent to the core, and an undoped cladding region abutting the down-doped cladding region,
wherein the core, and cladding are configured to support propagation of a spatially multiplexed optical signal comprising a plurality of desired modes, while suppressing undesired modes,
wherein the core and surrounding cladding is configured such that undesired modes have respective effective indices that are close to or less than the cladding index so as to result in leaky modes that leak into the outer cladding region, and
wherein the index spacing between the desired mode having the lowest effective index and the leaky mode with the highest effective index is sufficiently large so as to substantially prevent coupling therebetween.

2. The optical fiber of claim 1 wherein the maximum refractive index value of point a is greater than half of the value at n core .

3. The optical fiber of claim 1 wherein the optical fiber is a Few Mode Fiber designed for 2 to 10 modes.

4. An optical fiber, comprising:
a core and a cladding surrounding the core,
wherein the core and cladding have a refractive index profile that is structured to support propagation of a plurality of desired signal-carrying modes, while suppressing undesired modes,
wherein the core comprises an alpha core,
wherein the cladding comprises a down-doped trench abutting or adjacent to the core, and an undoped cladding region abutting the trench,
wherein the core, and cladding are configured to support propagation of a spatially multiplexed optical signal comprising a plurality of desired modes, while suppressing undesired modes,
wherein the core and surrounding cladding is configured such that undesired modes have respective effective indices that are close to or less than the cladding index so as to result in leaky modes that leak into the outer cladding region, and
wherein the index spacing between the desired mode having the lowest effective index and the leaky mode with the highest effective index is sufficiently large so as to substantially prevent coupling therebetween.

5. The optical fiber of claim 4 wherein the optical fiber is a Few Mode Fiber designed for 2 to 10 modes.

6. The optical fiber of claim 4 wherein the core comprises a truncated alpha core.

7. The optical fiber of claim 4 wherein the cladding comprises a ledge between the core and the trench.

8. The optical fiber of claim 4 wherein the refractive index profile has:
Truncated core radius: 5 to 20 microns
Ledge: 1 to 5 microns
Trench: 1 to 10 microns.

9. The optical fiber of claim 8 wherein the trench has a width of less than 3 microns.

Assignees

• Ofs Fitel Llc

Inventors

• Gruner-Nielsen Lars
• Lingle Robert L
• Peckham David W
• Sun Yi

Classifications

• G02B6/0288 Primary

  Multimode fibre, e.g. graded index core for compensating modal dispersion · CPC title