Wavelength-division-multiplexing optical circuit for photonic integrated circuits
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Solution Overview
Problem
Fabricating WDM filters for photonic integrated circuits (PICs) is challenging due to the need for very accurate dimensions of optical waveguides, which can lead to reduced yield and performance.
Innovation Solution
The proposed optical circuit includes a modulation stage, a multiplexing stage, and a polarization rotator and combiner (PRC) stage, which allows for larger fabrication tolerances and improved yield by relaxing the fabrication requirements for WDM filters in PICs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional WDM filters are used in PICs, then wavelength multiplexing function is achieved, but manufacturing precision requirements are extremely high leading to reduced yield
Solution Approach 1:
The patent divides the WDM filter function into multiple stages: a first stage that combines wavelengths with larger spacing (2Δλ) and a second stage that combines wavelengths with smaller spacing (Δλ). This segmentation allows each stage to operate with relaxed precision requirements, as the first stage handles coarse grouping while the second stage handles fine tuning, thereby improving overall yield while maintaining wavelength multiplexing functionality.
2Reliability
If stricter fabrication tolerances are enforced, then WDM filter performance is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent segments the wavelength combining process into two stages with different precision requirements. The first stage combines wavelengths spaced by 2Δλ using relaxed tolerance waveguides, while the second stage combines wavelengths spaced by Δλ using slightly more precise waveguides. This segmentation allows the system to achieve good overall performance without requiring all components to meet strict fabrication tolerances, thereby improving ease of manufacture.
Solution Approach 2:
The patent changes the channel spacing parameter between the two stages: the first stage handles larger spacing (2Δλ) which is easier to fabricate, while the second stage handles smaller spacing (Δλ). This parameter change allows the system to tolerate variations in waveguide dimensions while still achieving the required wavelength multiplexing performance, thus relaxing fabrication tolerance requirements.
3Device complexity
If a single-stage WDM filter is used, then device complexity is low, but fabrication precision requirements are extremely high
Solution Approach 1:
The patent segments the multiplexing function into two stages: a first stage that combines wavelengths with larger spacing and a second stage that combines wavelengths with smaller spacing. Although this increases device complexity compared to a single-stage filter, it significantly reduces the manufacturing precision requirements for each individual stage, making the overall system more manufacturable while maintaining effective wavelength multiplexing.
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 solution enables high-yield and low-cost production of WDM optical circuits in PICs, even with larger fabrication tolerances, thereby improving the performance and reliability of WDM transceivers.
Implementation Method 1
The PRC stage is configured to combine the signal sets into an output signal. The output signal has a first of the signal sets at a first polarization combined with a second of the signal sets at a second polarization orthogonal to the first polarization.
Data Source
AI summary
An optical circuit is used with continuous wave signals having different wavelengths at a channel spacing from one another. A portion of the optical circuit is implemented in a photonic integrated circuit. Modulators in a modulation stage modulate the continuous wave signals to produce modulated signals. A multiplexing stage, which can have multiplexing filters, power combiners, or power couplers, multiplexes the continuous wave or modulated signals to produce multiplexed signals. The multiplexing stage may be placed either before or after the modulation stage. One or more polarization rotator and combiner (PRC) devices in a final stage combines the multiplexed signals into an output signal. The output signal has a first set of the different wavelengths at a first polarization and has a second separate set of the different wavelengths at a second polarization orthogonal to the first polarization.