Coupled-Core Multi-Core Fiber Nonlinearity Mitigation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current optical communication systems face challenges in increasing data speed and reliability due to fiber nonlinearity, which is not effectively mitigated by existing technologies, especially as data requirements continue to rise.

Innovation Solution

The use of fibers with strong mode coupling and large modal delay, specifically through the implementation of coupled-core, multi-core fibers (CC-MCF) with different group velocities in each core, and intentionally designed large differential group delay (DGD) to match chromatic dispersion (CD) spreading, reduces impairments from nonlinearity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional single-mode fibers are used, then the fiber structure is simple and easy to manufacture, but fiber nonlinearity causes severe signal impairment and limits transmission capacity

Engineering Contradiction:

Improvesignal qualityVSAvoidfiber nonlinearity

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention divides the single fiber into multiple separate cores (e.g., seven cores arranged in a hexagonal pattern), where each core acts as an independent transmission channel. This segmentation allows the system to transmit multiple signals simultaneously through spatial division multiplexing, effectively increasing capacity while managing nonlinearity effects in each individual core.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention combines multiple separate cores into a single bundled structure that functions as one optical fiber. The cores are positioned close together and experience similar environmental conditions, allowing them to be managed as a unified system while benefiting from the nonlinearities being distributed across multiple channels rather than concentrated in one.

Inventive Principle:

Principle #5Merging (Combining)

2Productivity

If multiple cores are used to increase transmission capacity, then transmission density increases, but mode coupling and differential group delay cause signal mixing and interference

Engineering Contradiction:

Improvetransmission densityVSAvoidmode coupling management

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The invention introduces local variations in core properties, specifically differentiating the group velocity of each core through varied core sizes or refractive indices. This local quality differentiation creates controlled differential group delay between cores, which helps manage mode coupling effects and reduces signal interference while maintaining high transmission density.

Inventive Principle:

Principle #3Local quality

3Reliability

If differential group delay is increased to mitigate nonlinearity, then nonlinear impairments are reduced, but chromatic dispersion effects become more significant and require precise compensation

Engineering Contradiction:

Improvenonlinearity mitigationVSAvoiddispersion compensation accuracy

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The invention systematically varies key parameters including core size, refractive index, and spacing between cores to achieve the desired differential group delay. By changing these physical parameters during the fiber design and manufacturing process, the system optimizes the balance between nonlinearity mitigation and dispersion management, enabling precise control over signal characteristics.

Inventive Principle:

Principle #35Parameter changes

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

This approach significantly mitigates nonlinear impairments, allowing for increased transmission density and signal quality, with CC-MCF offering advantages over single-core fibers by requiring less DSP resources and maintaining performance even with small CD values.

Implementation Method 1

employing strong mode coupling and large modal delay... multiple cores that are strongly coupled such that signals carried in the multiple cores mix frequently and continuously

Methodology Applied

Scientific EffectMode coupling:

Implementation Method 2

employing strong mode coupling and large modal delay... providing a fiber exhibiting a large differential group delay (DGD)... any average spreading from the DGD is comparable to spreading resulting from chromatic dispersion

Methodology Applied

Scientific EffectDifferential group delay:

Implementation Method 3

any average spreading from the DGD is comparable to spreading resulting from chromatic dispersion (CD)

Methodology Applied

Scientific EffectChromatic dispersion: Dispersion (of waves)

Data Source

PatentUS10401564B2Fiber nonlinearity mitigation using strong mode coupling and large modal delay

Publication Date: 2019.09.03 NEC CORP

AI summary

Aspects of the present disclosure describe fiber nonlinearity induced transmission penalties are reduced both in fibers with large polarization-mode dispersion, and in coupled-core multicore fibers (CC-MCF). In the case of coupled multi-core fibers, the requirement for modal delay is less.