Asynchronous Optical Modulator Bias Control via Multi-Tone Dither

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Solution Overview

Problem

Asynchronous optical modulation systems face challenges in determining bias ϕ due to unknown and random delays τ, which obscure the feedback signal, making it difficult to adjust the transmission point of the optical modulator effectively.

Innovation Solution

The system generates multiple dither signals with specific frequency ratios, allowing the detector circuit to independently determine the feedback signal magnitude and sign components, thereby isolating the bias ϕ from the delay τ, and adjusts the transmission point based on these components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single dither signal is used in asynchronous optical modulation systems, then the system structure is simple, but the delay τ obscures the feedback signal making bias determination inaccurate

Engineering Contradiction:

Improvesystem structureVSAvoidbias determination accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The feedback signal determination is segmented into two independent components: magnitude determination using one dither signal and sign determination using another dither signal. This segmentation allows each component to be determined independently without being obscured by the delay τ, resolving the contradiction between simple structure and accurate measurement.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The feedback signal, which is normally a single scalar value, is decomposed into two separate dimensions: magnitude and sign. By determining these dimensions independently through different dither signals, the system achieves accurate bias determination without requiring complex synchronization mechanisms.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Measurement precision

If synchronous bias control is used, then the feedback signal can be determined accurately by accounting for delay, but the system requires complex synchronization between drive circuit and detector circuit

Engineering Contradiction:

Improvefeedback signal determination accuracyVSAvoidsynchronization mechanism

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The delay τ is extracted and isolated to only affect the sign determination component, while the magnitude determination remains independent of delay. This extraction allows accurate feedback signal determination without requiring complex synchronization between the drive circuit and detector circuit.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

A second dither signal with a different frequency is introduced as an intermediary to determine the sign of the feedback signal. This intermediary signal allows the system to obtain complete feedback information (magnitude and sign) without requiring synchronization, as the second dither signal's frequency relationship with the first allows delay-independent magnitude determination.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If multiple dither signals with specific frequency ratios are used, then the feedback signal can be determined independently of delay, but the device complexity increases

Engineering Contradiction:

Improvefeedback signal independence from delayVSAvoiddither signal generation

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The frequencies of the dither signals are specifically chosen to satisfy a rational ratio relationship. This parameter change in the frequency domain enables the magnitude determination to be independent of the time delay τ, achieving reliable feedback signal determination without complex delay compensation mechanisms.

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 enables accurate and unbiased feedback for adjusting the optical modulator's transmission point, improving the stability and quality of the optical data signal by eliminating the effects of random delays, ensuring reliable data transmission.

Implementation Method 1

a photodetector that detects a portion of the modulated optical signal

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Implementation Method 2

an optical modulation system that converts an electrical data signal into a phase-modulated and amplitude-modulated optical signal

Methodology Applied

Scientific EffectElectro-optic Effect: Electro-Optic Effects

Data Source

PatentUS10623105B2Asynchronous bias control for an optical modulator using a multiple tone detection technique with phase correction

Publication Date: 2020.04.14 INFINERA CORP

AI summary

In an asynchronous optical modulation system, a drive circuit may generate a plurality of dither tones in accordance with a predetermined dither frequency ratio. Based on the components of the dither frequency ratio, the optical modulation system may be configured to determine a feedback signal magnitude component that is independent of the delay τ and a feedback signal sign component that is also independent of the delay τ. A feedback signal that is independent of the delay τ can then be reconstructed based on the feedback signal magnitude component and the feedback signal sign component.