Frequency-Referenced Carrier Nonlinearity Cancellation

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Solution Overview

Problem

Current optical communication systems face limitations in mitigating nonlinear impairments in optical fiber links, particularly at longer distances and higher bit rates, as existing solutions fail to achieve the required performance and spectral efficiency while maintaining signal quality.

Innovation Solution

The use of frequency-locked or phase-referenced oscillators to pre-compensate and equalize nonlinear effects in optical communication systems, allowing for increased launch power and improved spectral utilization, enabling longer reach and performance without compromising signal quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of stationary object

If transmission power is increased to extend reach, then transmission distance is improved, but nonlinear impairments worsen

Engineering Contradiction:

Improvetransmission distanceVSAvoidnonlinear impairments

Core Design Contradiction:

Length of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The patent applies pre-compensation techniques where the nonlinear distortions are predicted and corrected before the signal is transmitted through the fiber. By calculating the expected nonlinear effects based on the transmitted signal characteristics and fiber parameters, the system pre-distorts the signal in the opposite direction, so that after propagation through the nonlinear medium, the signal is restored to its original form, thereby enabling higher launch powers without suffering from nonlinear impairments

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent employs feedback mechanisms where the received signal is analyzed to estimate the nonlinear distortions that occurred during transmission. This estimated distortion information is fed back to the transmitter or used in digital signal processing at the receiver to compensate for the nonlinear effects. The feedback loop allows the system to adapt to actual transmission conditions and continuously correct nonlinear impairments, enabling extended transmission distances at higher power levels

Inventive Principle:

Principle #23Feedback

2Reliability

If transmission power is reduced to avoid nonlinear effects, then signal quality is maintained, but spectral efficiency deteriorates

Engineering Contradiction:

Improvesignal qualityVSAvoidspectral efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

By applying pre-compensation for nonlinear effects, the system allows transmission at higher power levels without degrading signal quality. The pre-calculated compensation signals are combined with the data signals before transmission, enabling the system to operate at optimal power levels that maximize spectral efficiency while maintaining signal integrity through the nonlinear compensation process

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the parameters of the transmitted signal by applying pre-distortion that accounts for nonlinear effects. By modifying the signal characteristics in advance based on predicted nonlinear behavior, the system enables transmission at higher power levels with improved spectral efficiency while the nonlinear effects during propagation transform the signal back to the desired form, maintaining signal quality

Inventive Principle:

Principle #35Parameter changes

3Object-affected harmful factors

If dispersion engineering is used to mitigate nonlinear effects, then nonlinear impairments are reduced, but system complexity increases

Engineering Contradiction:

Improvenonlinear impairmentsVSAvoidsystem complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent replaces physical dispersion engineering approaches with digital signal processing techniques. Instead of requiring complex fiber design and dispersion management hardware, the system uses computational algorithms to model and compensate for nonlinear effects. This substitution of mechanical/physical approaches with electronic/digital methods reduces system complexity while achieving comparable or superior nonlinear mitigation performance

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Reliability

If electronic equalization is applied to compensate nonlinear effects, then signal quality is improved, but computational complexity increases

Engineering Contradiction:

Improvesignal qualityVSAvoidcomputational complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent reduces computational complexity by performing the bulk of nonlinear compensation work in advance during the pre-compensation stage at the transmitter. By calculating and applying the compensation signals before transmission, the system avoids the need for complex real-time iterative equalization algorithms at the receiver. The remaining computational task at the receiver is significantly simplified, maintaining signal quality while reducing overall computational complexity

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11418260B2Nonlinearity cancellation in fiber optic transmission based on frequency-mutually-referenced carriers

Publication Date: 2022.08.16 RGT UNIV OF CALIFORNIA

AI summary

A system and method for mitigating nonlinearity in an optical communication link with multiple carriers uses mutual frequency referencing to stabilize at least a portion of the multiple carriers. Using at least one frequency-referenced signal, carrier nonlinearity can be determined and compensated within the link by pre-distortion, back-propagation, or a combination of both. Mutual frequency referencing may be performed at the emitting end of the link, at the receiving end, or a combination of both.