Coupled Resonator Optical Waveguide Delay Line Design
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Solution Overview
Problem
Conventional optical delay lines based on waveguides face challenges with higher-order dispersion, leading to signal distortion, particularly in achieving constant delay and amplitude across a frequency spectrum.
Innovation Solution
The use of coupled resonator optical waveguides (CROW) with tailored coupling coefficients and a reflecting configuration to achieve an all-pass Bessel filter, ensuring constant group delay and amplitude over a prescribed bandwidth by controlling the group velocity of optical signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional optical waveguides are used for delay lines, then the waveguide length can be greatly reduced by reducing group velocity, but higher-order dispersion causes signal distortion
Solution Approach 1:
The waveguide is segmented into a series of coupled resonators (micro rings) rather than using a continuous waveguide structure. This segmentation allows the light to propagate through discrete resonant elements, enabling control over group velocity and dispersion characteristics independently, thus achieving compact delay lines without signal distortion
Solution Approach 2:
The resonant frequencies and coupling coefficients of the resonators are carefully designed and tuned to achieve desired group velocity and minimize higher-order dispersion. By adjusting these parameters, the system achieves constant group delay across the operating bandwidth while maintaining compact dimensions
2Length of stationary object
If grating structures or CROW are used to achieve slow light, then the waveguide length is reduced, but higher-order dispersion causes signal distortion
Solution Approach 1:
Different resonators in the coupled-resonator waveguide can have different resonant frequencies and coupling coefficients, allowing local optimization of dispersion characteristics. This enables precise control over group velocity and higher-order dispersion terms across different sections of the delay line
Solution Approach 2:
The system allows for dynamic tuning of resonant frequencies and coupling coefficients to optimize performance for different operating conditions and signal wavelengths, providing adaptability in dispersion control
3Speed
If the group velocity approaches zero at frequencies close to band edges, then slow light is achieved, but higher-order dispersion increases causing signal distortion
Solution Approach 1:
The resonator parameters are pre-designed and optimized before operation to ensure that the operating frequency remains within the passband away from band edges. This preliminary design prevents the group velocity from approaching zero while still achieving the desired delay, thereby avoiding the dispersion-induced signal distortion that occurs near band edges
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 results in an ideal optical delay line with constant group delay and amplitude, minimizing signal distortion and enhancing the delay-bandwidth product, while maintaining efficiency and precision in optical signal processing.
Implementation Method 1
providing coupled resonator optical waveguides (CROW) comprising a plurality of resonators
Implementation Method 2
Another mechanism is the Bragg waveguiding, in which waveguiding is achieved through Bragg reflection from a periodic structure
Implementation Method 3
setting a coupling distance between each resonator of the CROW
Implementation Method 4
achieve an all-pass Bessel filter, ensuring constant group delay and amplitude over a prescribed bandwidth
Data Source
AI summary
Coupled-resonator optical waveguides (CROW) can be used to control a speed of an optical signal. In particular, the coupling distance between the resonators can be adjusted to precisely control a group delay of an optical wave. Systems and methods are described to control such coupling distance in a CROW.