Photonic lantern spatial multiplexers with mode selectivity

Patent metadata

Field	Value
Publication number	US-9411100-B2
Application number	US-201314033033-A
Country	US
Kind code	B2
Filing date	Sep 20, 2013
Priority date	Sep 20, 2013
Publication date	Aug 9, 2016
Grant date	Aug 9, 2016

Abstract

A photonic lantern spatial multiplexer that provides mode selectivity includes a multimode optical waveguide and a plurality of single mode optical waveguides. The single mode cores of the single mode optical waveguides merge with the multimode core of the multimode optical waveguide. At least two of the single mode cores have different respective single mode effective refractive indexes.

First claim

What is claimed is:

1. An apparatus, comprising:
a multimode optical waveguide having a multimode core;
a plurality of single mode optical waveguides, each having one of a corresponding plurality of respective single mode cores;
an adiabatically tapered capillary tube, the multimode core and the single mode cores located within the adiabatically tapered capillary tube, wherein the single mode cores merge with the multimode core; and
wherein respective single mode effective refractive indexes of at least two of the single mode cores are different.

2. The apparatus of claim 1 , wherein:
each of the single mode optical waveguides is configured to guide a different one of a plurality of transverse modes along a respective length thereof; and
the multimode optical waveguide is configured to guide a plurality of transverse multimodes along a length thereof.

3. The apparatus of claim 2 , wherein each non-degenerate transverse mode of the plurality of transverse modes maps to one of the plurality of transverse multimodes based on respective single mode effective refractive indexes of the single mode optical waveguides and each degenerate transverse mode of the plurality of transverse modes maps to a select number of the plurality of transverse multimodes based on the respective single mode effective refractive indexes, the select number of transverse multimodes corresponding to a particular degenerate transverse mode being equal to a number of single mode cores configured to carry the particular degenerate transverse mode.

4. The apparatus of claim 3 , wherein a first single mode core having a first single mode effective refractive index is configured to adiabatically couple a first non-degenerate transverse mode of an optical signal to a first transverse multimode associated with a first multimode effective refractive index of the multimode optical waveguide, the first single mode effective refractive index being greater than a respective single mode refractive index of each single mode core of the remaining plurality of single mode cores, and the first multimode effective refractive index being greater than any of other multimode effective refractive indexes associated with other transverse multimodes of said multimode optical waveguide.

5. The apparatus of claim 4 , wherein a second single mode core having a second single mode effective refractive index is configured to adiabatically couple a second non-degenerate transverse mode of an optical signal to a second transverse multimode associated with a second multimode effective refractive index of the multimode optical waveguide, the second single mode effective refractive index being less than the first single mode effective refractive index and greater than a respective single mode refractive index of each single mode core of the remaining plurality of single mode cores, and the second multimode effective refractive index being less than the first multimode effective refractive index and greater than any of other multimode effective refractive indexes associated with other transverse multimodes of said multimode optical waveguide.

6. The apparatus of claim 1 , wherein at least two of the single mode cores have different respective diameters.

7. The apparatus of claim 6 , wherein a first single mode core has a first diameter and a first effective refractive index and a second single mode core has a second greater diameter and a second greater effective refractive index.

8. The apparatus of claim 1 , wherein the at least two of the single mode cores include at least one dopant, the single mode effective refractive indexes of the at least two single mode cores being determined based at least on a concentration of the at least one dopant.

9. The apparatus of claim 1 , wherein each of the single mode optical waveguides is a three-dimensional waveguide or an optical fiber.

10. An apparatus, comprising:
a multimode optical waveguide having a multimode core;
a plurality of single mode optical waveguides, each having a respective single mode core, the single mode cores tapering to merge with the multimode core and wherein at least two of the single mode cores have different respective diameters; and
a cladding layer surrounding the plurality of single mode optical waveguides, the cladding layer forming the multimode core upon tapering of the single mode cores.

11. An apparatus, comprising:
a multimode optical waveguide having a multimode core;
a plurality of single mode optical waveguides, each having a respective single mode core; and
a photonic lantern spatial demultiplexer configured such that the single mode cores merge with the multimode core,
wherein each of the plurality of single mode optical waveguides is configured to guide a different one of a plurality of transverse modes along a respective length thereof,
wherein the multimode optical waveguide is configured to guide a plurality of transverse multimodes along a length thereof,
wherein the respective length of each of the plurality of single mode optical waveguides compensates for a differential group delay between the transverse modes after transmission through the multimode optical waveguide; and
wherein respective single mode effective refractive indexes of at least two of the single mode cores are different.

12. The apparatus of claim 11 , wherein the photonic lantern spatial demultiplexer further includes a capillary tube, the capillary tube being adiabatically tapered to merge the single mode cores with the multimode core.

13. The apparatus of claim 11 , further comprising:
a plurality of variable optical attenuators, each coupled to a respective one of the plurality of single mode optical waveguides, each of the variable optical attenuators operable to attenuate a respective one of the transverse modes on a respective one of the plurality of single mode optical waveguides.

14. The apparatus of claim 13 , further comprising:
a controller coupled to the plurality of variable optical attenuators and operable to set a respective attenuation amount of each of the plurality of variable optical attenuators such that the optical power of each of the transverse modes is substantially equal.

15. The apparatus of claim 11 , wherein each non-degenerate transverse mode of the plurality of transverse modes maps to one of the plurality of transverse multimodes based on respective single mode effective refractive indexes and each degenerate transverse mode of the plurality of transverse modes maps to a select number of the plurality of transverse multimodes based on the respective single mode effective refractive indexes, the select number of transverse multimodes corresponding to a particular degenerate transverse mode being equal to a number of single mode cores configured to carry the particular degenerate transverse mode.

16. The apparatus of claim 11 , wherein the at least two of the single mode cores have different respective diameters, each corresponding to the different respective single mode effective refractive indexes.

17. The apparatus of claim 11 , wherein each of the single mode cores has substantially the same diameter and at least two of the single mode cores include at least one dopant, the single mode effective refractive indexes of each of the at least two single mode cores being different based on a concentration of the at least one dopant.

18. The apparatus of claim 10 , wherein:
each of the single mode optical waveguides is configured to guide a different one of a plurality of transverse modes along a respective length thereof; and

Assignees

• Alcatel Lucent Usa Inc
• Alcatel Lucent

Inventors

• Fontaine Nicolas K
• Ryf Roland

Classifications

• G02B6/02042

  Multicore optical fibres · CPC title

• G02B6/2821

  using lateral coupling between contiguous fibres to split or combine optical signals · CPC title

• G02B6/0288

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

• H04J14/04

  Mode multiplex systems · CPC title

• G02B6/14 Primary

  Mode converters · CPC title