Optical Hybrid Waveguide Tapering for Phase Error Reduction
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Solution Overview
Problem
Optical coherent receivers face challenges with phase errors due to waveguide imperfections, particularly in multi-mode waveguides, which degrade performance and require complex active tuning or increased power consumption.
Innovation Solution
The design incorporates wide waveguides with controlled bends and a figure of merit (FoM) optimization, ensuring each waveguide has a consistent optical path length and reduced width variation to minimize phase errors, eliminating the need for active phase tuning and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If waveguide bends are used to route optical signals in multi-mode waveguides, then the optical path can be configured, but phase errors are introduced due to coupling into higher order modes
Solution Approach 1:
The patent changes the geometric parameters of the waveguide, specifically using a tapered waveguide design where the width varies along the propagation direction. This parameter change transforms the waveguide mode distribution, allowing it to support multiple modes while reducing the phase errors typically introduced by bends in uniform waveguides. The tapered structure gradually transitions the optical field distribution, minimizing abrupt mode coupling and associated phase errors.
2Measurement precision
If active phase tuning is implemented to correct phase errors, then phase accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent implements a self-service mechanism where the tapered waveguide structure inherently compensates for phase errors through its geometric design. The varying width creates a distributed phase correction effect along the waveguide path, eliminating the need for external active phase tuning elements. The waveguide structure serves its own phase correction function, reducing device complexity and power consumption while maintaining high phase accuracy.
3Reliability
If waveguide width variation is increased to reduce mode coupling, then phase error is reduced, but manufacturing precision requirements are affected
Solution Approach 1:
The patent applies preliminary action by pre-compensating for phase errors through the designed width variation profile in the tapered waveguide. The width variation is carefully calculated and implemented during the fabrication design phase to proactively counteract the phase errors that would otherwise be introduced by bends and mode coupling. This preliminary geometric compensation reduces the need for post-fabrication tuning and relaxes the stringency of manufacturing tolerances.
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 configuration significantly reduces phase errors, improves performance, and simplifies the optical coherent receiver design by eliminating the requirement for phase shifters, leading to lower power consumption and reduced complexity.
Implementation Method 1
A waveguide can be fabricated on and/or in a photonic integrated circuit, and can be used for efficient coupling or routing
Data Source
AI summary
An optical coherent receiver includes a 90-degree optical hybrid configured to receive an input signal and a reference signal, and mix the input signal with four quadrature states associated with the reference signal to generate four output signals. The 90-degree optical hybrid includes a plurality of 3-dB couplers; and a plurality of optical waveguides, wherein each optical waveguide of the plurality of optical waveguides couples two respective 3-dB couplers of the plurality of 3-dB couplers, and wherein each optical waveguide of the plurality of optical waveguides has a same optical path length. Each optical waveguide of the plurality of optical waveguides is dimensioned according to a figure of merit (FoM) to reduce a phase error.