Optoelectronic QAM Modulator Reducing Optical Loss

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Solution Overview

Problem

Conventional optoelectronic devices for quadrature-amplitude modulation (QAM) face significant optical loss and practicality issues due to the use of nested Mach-Zehnder in-phase modulators and ring resonator modulations, which lead to high power consumption and sensitivity to environmental conditions.

Innovation Solution

An optoelectronic device comprising an input waveguide, two intermediate waveguides with modulating and phase shifting components connected to electronic drivers, and an output waveguide, which enables QAM-N modulation without the need for digital-to-analogue converters and with lower power consumption, using components like electro-absorption modulators and DC phase shifters to produce a compact and efficient transmitter.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If nested Mach-Zehnder in-phase modulators are used for QAM modulation, then QAM modulation capability is achieved, but optical loss increases significantly

Engineering Contradiction:

ImproveQAM modulation capabilityVSAvoidoptical loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent divides the modulation function into separate modules: a PAM modulator for amplitude modulation and a separate phase modulator for phase modulation. This segmentation allows each module to be optimized independently and avoids the nested structure that causes cumulative 3dB loss in conventional approaches.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent combines the PAM modulator and phase modulator into a single integrated device structure that shares common components like the waveguide and driver electronics. This merging reduces the total number of optical components and coupling interfaces, thereby reducing overall optical loss while maintaining QAM modulation capability.

Inventive Principle:

Principle #5Merging (Combining)

2Adaptability or versatility

If ring resonator modulations are used for QAM modulation, then QAM modulation capability is achieved, but sensitivity to environmental conditions increases

Engineering Contradiction:

ImproveQAM modulation capabilityVSAvoidsensitivity to environmental conditions

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces ring resonator-based modulation (which relies on mechanical/thermal effects for phase shifting) with electro-absorption modulators that use the electro-optic effect. This substitution eliminates the need for thermal tuning and feedback control systems, thereby reducing sensitivity to environmental conditions while maintaining QAM modulation capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If nested Mach-Zehnder in-phase modulators are used for QAM modulation, then QAM modulation capability is achieved, but device complexity increases

Engineering Contradiction:

ImproveQAM modulation capabilityVSAvoiddevice complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent extracts the phase modulation function from the nested Mach-Zehnder structure and implements it as a separate, simplified phase modulator module. This extraction allows the phase modulation to be performed without requiring multiple 3dB couplers and nested interferometers, thereby reducing device complexity while maintaining QAM capability.

Inventive Principle:

Principle #2Taking out (Extraction)

4Adaptability or versatility

If ring resonator modulations are used for QAM modulation, then QAM modulation capability is achieved, but power consumption increases

Engineering Contradiction:

ImproveQAM modulation capabilityVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The patent replaces thermally-driven ring resonator modulation with electro-absorption modulators that use voltage-driven electro-optic effects. This substitution eliminates the need for power-intensive thermal tuning and feedback control circuits, thereby significantly reducing overall power consumption while maintaining QAM modulation capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 device achieves efficient QAM-N modulation with reduced power consumption and simpler driver signals, maintaining high integration density and stability across various environmental conditions.

Implementation Method 1

a first electro-absorption modulator, coupled to receive light from the input waveguide, and operable to produce a first output or a second output

Methodology Applied

Scientific EffectElectro-absorption: Absorption (EM radiation)

Implementation Method 2

a phase shifter, coupled to the electro-absorption modulator

Methodology Applied

Scientific EffectPhase shifting: Refraction

Data Source

PatentUS11296794B2Optical modulator and method of use

Publication Date: 2022.04.05 ROCKLEY PHOTONICS LTD

AI summary

An optoelectronic device for quadrature-amplitude modulation (QAM) and a method of modulating light according to the same. The device comprising: an input waveguide; two intermediate waveguides, each coupled to the input waveguide via an input coupler; and an output waveguide, coupled to each of the intermediate waveguides via an output coupler; wherein each intermediate waveguide includes a modulating component connected in series with a phase shifting component, and each modulating component is connected to a respective electronic driver, the electronic drivers together being operable to produce a QAM-N modulated output from light entering the device from the input waveguide.