Deterministic Scrambler for Multimode Optical Fiber Dispersion

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Solution Overview

Problem

Multimode optical fibers face limitations in bandwidth and data transmission capacity due to modal dispersion and mode-dependent loss, which are not adequately addressed by existing scramblers that require a large number of random mode-scramblers and provide limited performance.

Innovation Solution

A deterministic scrambler that permutes modes based on power values associated with waveguide modes to reduce modal dispersion and mode-dependent loss, requiring a small number of mode-scramblers and improving performance by redistributing optical signals efficiently.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a large number of random mode-scramblers are used to mitigate modal dispersion and mode-dependent loss, then the performance improvement is limited, but the device complexity increases significantly

Engineering Contradiction:
ImproveperformanceVSAvoidnumber of scramblers
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the fundamental parameter of scrambling from random to deterministic based on power values. By calculating power values for each mode and deterministically selecting which modes to scramble based on these power values, the system achieves better performance with fewer scramblers. This parameter change transforms the scrambling mechanism from stochastic to controlled, resolving the contradiction between performance and complexity.

Inventive Principle:
Principle #35Parameter changes

2Object-affected harmful factors

If conventional random scramblers are used to reduce mode-dependent loss, then some mitigation is achieved, but the bit error rate remains suboptimal

Engineering Contradiction:
Improvemode-dependent lossVSAvoidbit error rate
Core Design Contradiction:
Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent introduces feedback by calculating power values for each mode based on the actual signal characteristics and using this information to guide the scrambling selection. The system measures or estimates the power in each mode, then uses this feedback to deterministically select which modes to scramble, achieving optimal balance between mitigating mode-dependent loss and maintaining low bit error rate.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent changes the scrambling approach from random to deterministic based on power values. By calculating power values for each mode and deterministically selecting which modes to scramble based on these power values, the system achieves better performance with fewer scramblers. This parameter change transforms the scrambling mechanism from stochastic to controlled, resolving the contradiction between performance and complexity.

Inventive Principle:
Principle #35Parameter changes

3Productivity

If multimode fiber is used to support high data rates at short distances, then bandwidth is sufficient, but modal dispersion limits the information carrying capacity

Engineering Contradiction:
Improvedata rateVSAvoidinformation carrying capacity
Core Design Contradiction:
ProductivityVSLoss of information

Solution Approach 1:

The patent changes the fundamental parameter of scrambling from random to deterministic based on power values. By calculating power values for each mode and deterministically selecting which modes to scramble based on these power values, the system achieves better performance with fewer scramblers. This parameter change transforms the scrambling mechanism from stochastic to controlled, resolving the contradiction between performance and complexity.

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

The deterministic scrambler effectively mitigates the impact of modal dispersion and mode-dependent loss, achieving improved bit error rate and reduced mode-dependent loss, while requiring fewer scramblers compared to conventional approaches, thus enhancing the capacity and reliability of optical fiber transmission systems.

Implementation Method 1

When the light launched into the core strikes the cladding, it undergoes a number of internal reflections.

Methodology Applied
Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

In a multimode fiber, the time taken by light to travel through a fiber is different for each mode, which results in a spreading of the pulse at the output of the fiber (which is referred to as 'intermodal dispersion').

Methodology Applied
Scientific EffectModal dispersion: Dispersion (of waves)

Data Source

PatentEP3273623B1Optical fiber transmission link with multimode optical fiber and scrambler
Publication Date: 2024.09.18 INSTITUT MINES TELECOM TELECOM BRETAGNE
  • EP3273623B1 patent drawingFigure 1~2
  • EP3273623B1 patent drawingFigure 3
  • EP3273623B1 patent drawingFigure 4

AI summary

Embodiments of the invention provides a deterministic scrambler (1) arranged in a multimode optical fiber (130) for scrambling light, the light comprising a set of optical signals propagated in said multimode optical fiber according to a set of propagation modes, each propagation mode being associated with a power value, wherein the scrambler is configured to determine a permutation of said propagation modes depending on the power values associated with said propagation modes, the scrambler being configured to redistribute the optical signals according to said permutation of the propagation modes.