Few-Mode Fiber Multiplexing with Combined Degenerate Modes

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Solution Overview

Problem

Existing mode division multiplexing in few-mode fibers faces high crosstalk issues due to degenerate modes with the same effective refractive index, leading to unpredictable light transfer between these modes.

Innovation Solution

A multiplexer/demultiplexer system that combines light from degenerate modes into a single data channel, using metasurface elements to control polarization and phase, allowing bidirectional propagation while isolating signals from each other.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If mode division multiplexing is used in few-mode fibers, then signal transmission capacity is improved, but crosstalk between degenerate modes increases

Engineering Contradiction:

Improvesignal transmission capacityVSAvoidcrosstalk between modes

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent combines multiple degenerate modes (specifically LP11a and LP11b modes) into a single data channel at the transmitter. By merging these modes before transmission and separating them coherently at the receiver, the system achieves high-capacity transmission while eliminating crosstalk issues that would otherwise occur between the degenerate modes during propagation through the few-mode fiber.

Inventive Principle:

Principle #5Merging (Combining)

2Productivity

If degenerate modes are used for multiplexing, then more data channels can be transmitted, but signal separation becomes unpredictable

Engineering Contradiction:

Improvenumber of data channelsVSAvoidsignal separation accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The system employs coherent detection with feedback control to track and compensate for phase variations between degenerate modes during transmission. The receiver uses pilot tones and phase-locked loops to maintain accurate phase relationships, enabling precise separation of the combined modes despite their degeneracy and the fiber's modal dispersion characteristics.

Inventive Principle:

Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Reduces crosstalk between degenerate modes by combining them into a single data channel, achieving low loss transmission and effective signal separation.

Implementation Method 1

using metasurface elements to control polarization and phase

Methodology Applied

Scientific EffectPolarization control: Polarisation

Implementation Method 2

using metasurface elements to control polarization and phase

Methodology Applied

Scientific EffectPhase control:

Implementation Method 3

transfer a first optical data signal between a first single-mode fiber and a first propagation mode of a few-mode fiber, the first propagation mode having a first effective refractive index

Methodology Applied

Scientific EffectMode propagation: Refraction

Data Source

PatentUS20260012282A1Mode division multiplexing using combined degenerate modes

Publication Date: 2026.01.08 CORNING INC

AI summary

An optical communication system can include a multiplexer/demultiplexer. The multiplexer/demultiplexer can transfer a first optical data signal between a first single-mode fiber and a first propagation mode of a few-mode fiber. The first propagation mode can have a first effective refractive index. The multiplexer/demultiplexer can transfer a second optical data signal between a second single-mode fiber and a combination of a second propagation mode of the few-mode fiber and a third propagation mode of the few-mode fiber. The second propagation mode and the third propagation mode can have a same effective refractive index that differs from the first effective refractive index. During propagation within the few-mode fiber, the second optical data signal can couple bidirectionally between the second propagation mode and the third propagation mode, while being substantially isolated from the first optical data signal in the first propagation mode.