Electrical Domain Dispersion Compensation for Optical Signals

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Solution Overview

Problem

Optical communications systems face significant challenges in mitigating dispersion effects, which limit signal reach and increase costs due to the need for expensive optical compensators and amplifiers, especially when dealing with high bandwidth and non-ideal light sources.

Innovation Solution

The method involves digitally filtering communications signals in the electrical domain using a compensation function to generate a predistorted signal that compensates for chromatic dispersion and component non-linearities, allowing for effective dispersion compensation regardless of the detection type used in the receiver.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If optical dispersion compensators are used to compensate for chromatic dispersion, then signal quality is improved, but system cost and device complexity increase significantly

Engineering Contradiction:

Improvesignal qualityVSAvoidsystem cost

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces optical domain dispersion compensation mechanisms (optical compensators, dispersion compensation modules) with electrical domain signal processing. The core invention uses electrical filtering and equalization techniques applied to the detected electrical signal to compensate for chromatic dispersion effects, thereby eliminating the need for complex optical compensators and reducing system cost and complexity while maintaining signal quality

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the domain of dispersion compensation from optical frequency domain to electrical time domain. By transforming the compensation function into the electrical domain and applying it through digital or analog filtering, the system achieves dispersion compensation without requiring optical components that operate in the optical domain, thus simplifying the overall system architecture

Inventive Principle:

Principle #35Parameter changes

2Length of moving object

If optical amplifiers are deployed to extend signal reach, then transmission distance is improved, but noise accumulation and cost increase

Engineering Contradiction:

Improvesignal reachVSAvoidnoise accumulation

Core Design Contradiction:

Length of moving objectVSLoss of energy

Solution Approach 1:

The patent replaces optical amplification with electrical domain signal regeneration and processing. By performing dispersion compensation and signal equalization in the electrical domain after detection, the system can extend signal reach without introducing additional optical noise that would result from cascaded optical amplifiers

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces an electrical domain intermediary processing stage between optical detection and final signal recovery. This electrical processing stage acts as a mediator that can compensate for dispersion and extend reach without requiring optical amplification, thereby avoiding noise accumulation from optical amplifiers while still achieving extended signal transmission distance

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If electrical domain compensation is implemented, then system cost and complexity are reduced, but adaptation to different detection types is limited

Engineering Contradiction:

Improvesystem costVSAvoiddetection type compatibility

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent creates a universal electrical domain compensation framework that can be applied to multiple detection types including direct detection, coherent detection, and differential detection. The electrical filtering and equalization techniques described are detection-type agnostic and can be adapted to various receiver architectures, thereby achieving both cost reduction and broad adaptability

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9559778B2Optical dispersion compensation in the electrical domain in an optical communications system

Publication Date: 2017.01.31 CIENA CORP

AI summary

Optical dispersion imposed on a communications signal conveyed through an optical communications system is compensated by modulating the communications signal in the electrical domain. A compensation function is determined that substantially mitigates the chromatic dispersion. The communications signal is then modulated in the electrical domain using the compensation function. In preferred embodiments, compensation is implemented in the transmitter, using a look-up-table and digital-to-analog converter to generate an electrical predistorted signal. The electrical predistorted signal is then used to modulate an optical source to generate a corresponding predistorted optical signal for transmission through the optical communications system.