Digital Nonlinear Phase Compensator for Submarine Cables

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Solution Overview

Problem

Legacy submarine fiber optic links face challenges due to higher nonlinearities caused by dispersion management features, limiting the data capacity and requiring costly upgrades to improve dispersion compensation.

Innovation Solution

A coherent optical receiver system that generates multiple data streams, calculates aggregate power, applies an adjustable temporal low pass filter, and phase-rotates the data streams to compensate for nonlinearities, extending the life of dispersion compensation fiber and enhancing performance in wavelength division multiplexing environments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If dispersion management features are added to legacy submarine fiber optic links, then dispersion is compensated and signal quality is improved, but nonlinearities increase and data capacity is limited

Engineering Contradiction:

Improvesignal qualityVSAvoidnonlinearities

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the parameter of dispersion by dynamically adjusting the dispersion compensation value based on the detected nonlinear phase rotation. The system measures the nonlinear phase rotation of received optical signals and uses this information to calculate an appropriate dispersion compensation value, thereby optimizing the balance between dispersion compensation and nonlinear effect mitigation.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If higher power is used per channel in subsea optical communication systems, then data capacity is improved, but nonlinearities increase and performance degrades

Engineering Contradiction:

Improvedata capacityVSAvoidnonlinearities

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent implements a feedback mechanism where the receiver detects the nonlinear phase rotation of incoming optical signals and feeds this information back to adjust the dispersion compensation value. This closed-loop system continuously optimizes the compensation parameters based on the actual nonlinear conditions, allowing the system to maintain high data capacity while mitigating nonlinear effects through adaptive parameter adjustment.

Inventive Principle:

Principle #23Feedback

3Reliability

If fixed DCF is installed in subsea links, then dispersion compensation is achieved, but the dispersion map remains fixed and cannot be optimized for modern coherent line cards

Engineering Contradiction:

Improvedispersion compensationVSAvoiddispersion map flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent transforms the static dispersion compensation approach into a dynamic system. Instead of relying on fixed DCF with a predetermined dispersion map, the system dynamically adjusts the dispersion compensation value based on real-time detection of nonlinear phase rotation. This enables the dispersion compensation to adapt to different operating conditions and modern coherent line card requirements without requiring physical changes to the submarine cable infrastructure.

Inventive Principle:

Principle #15Dynamics

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 solution effectively mitigates nonlinearities, extending the life of dispersion compensation fiber and improving performance by optimizing power compensation and phase rotation, thereby enhancing data capacity and reducing the need for costly upgrades.

Implementation Method 1

applies an adjustable temporal low pass filter to the first aggregate power and the second aggregate power resulting in a compensation power

Methodology Applied

Scientific EffectLow pass filter: Filter (electronic)

Implementation Method 2

phase-rotates the first data streams and the second data streams proportional to the compensation power

Methodology Applied

Scientific EffectPhase rotation: Phase Modulation

Data Source

PatentUS11018767B2Digital nonlinear phase compensator for legacy submarine cables

Publication Date: 2021.05.25 INFINERA CORP

AI summary

A method and system are herein disclosed. A coherent optical receiver receives a first optical data carrier signal at a first instant of time and a second optical data carrier signal at a second instant of time, generates at least four first data streams from the first optical data carrier signal and at least four second data streams from the second optical data carrier signal; and circuitry calculates a first aggregate power of the first data streams and a second aggregate power of the second data streams; applies an adjustable temporal low pass filter to the first aggregate power and the second aggregate power resulting in a compensation power, the adjustable temporal low pass filter adjusted to achieve a performance metric; and phase-rotates the first data streams and the second data streams proportional to the compensation power.