Optical Multi/Demultiplexing Circuit With Multimode Waveguide
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical wavelength multi/demultiplexing circuits face challenges in achieving broad transmission bandwidth, reducing transition region width between wavelength channels, and flattening phase spectra while maintaining low loss and loss flatness, particularly due to issues with parallel waveguide connection-type synchronized AWGs that result in increased loss variation and wavelength dispersion.
Innovation Solution
The implementation of a synchronized AWG-type optical wavelength multi/demultiplexing circuit using a multimode waveguide connection configuration with an asymmetric Mach-Zehnder interferometer and a mode converter/multiplexer, which optimizes the optical frequency response to achieve low loss and flat transmission characteristics by convolving the field shapes of fundamental and higher-order modes, and adjusting the optical delay lines to ensure the electric field amplitude remains centered and linearly dependent on signal wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If parallel waveguide connection-type synchronized AWG is used, then transmission bandwidth is broadened, but loss variation increases and wavelength dispersion occurs
Solution Approach 1:
A multimode waveguide is introduced as an intermediary component between the input waveguide and the AWG. This multimode waveguide supports multiple propagation modes (fundamental mode and higher-order modes) that interact with the AWG to flatten the transmission spectrum and reduce loss variation, while maintaining broad transmission bandwidth through proper mode coupling design.
Solution Approach 2:
The optical delay lengths of the delay lines are specifically designed to satisfy particular mathematical relations (Eq. 1 and Eq. 2 in the patent) that create constructive interference at desired wavelengths. By adjusting the delay length difference ΔL and optical frequency repetition period FSR to satisfy these relations, the transmission characteristics are optimized to reduce loss variation while maintaining broad bandwidth.
2Area of stationary object
If transmission bandwidth is broadened, then transition region width between wavelength channels should be reduced, but loss flatness becomes difficult to maintain
Solution Approach 1:
An asymmetric Mach-Zehnder interferometer configuration is employed where the two arms have different optical path lengths. This asymmetry is deliberately designed to create specific interference patterns that flatten the transmission spectrum. The asymmetric structure allows independent optimization of the transmission band characteristics, enabling broad bandwidth while maintaining loss flatness through proper design of the asymmetry parameters.
Solution Approach 2:
The optical delay lines are designed with periodic optical delay length differences that create constructive and destructive interference patterns at regular wavelength intervals. This periodic structure, when properly tuned to satisfy the patent's mathematical relations, produces a flattened transmission spectrum with reduced loss variation across the broad transmission band, while maintaining narrow transition regions between channels.
3Manufacturing precision
If asymmetric Mach-Zehnder interferometer is used to flatten transmission spectrum, then phase flatness is improved, but device complexity increases
Solution Approach 1:
The multimode waveguide serves multiple functions simultaneously: it acts as a mode converter, an interferometer arm, and a spectral shaping element. By integrating these functions into a single component rather than using separate elements, the device achieves phase flatness through the asymmetric Mach-Zehnder interferometer effect while minimizing overall device complexity. The multimode waveguide structure itself provides the interference mechanism needed for spectrum flattening.
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 results in a high rectangular transmission loss spectrum with reduced loss variation and phase flatness, maintaining low loss and broadening the transmission bandwidth while minimizing the guard bandwidth, effectively addressing the limitations of previous technologies.
Implementation Method 1
an Arrayed Waveguide Grating (hereinafter, AWG)
Implementation Method 2
synchronizing the multi/demultiplexing characteristics of two AWGs
Implementation Method 3
a Mach-Zehnder interferometer (hereinafter, MZI) 304 having a directional coupler 303 composed of two proximal waveguides
Implementation Method 4
2N optical delay lines (N being a positive integer greater than or equal to 2) having mutually different optical delay lengths
Data Source
AI summary
Provided is an optical wavelength multi/demultiplexing circuit with a high rectangular transmission loss spectrum that is able to secure loss flatness of a transmission band, maintain/reduce a guard bandwidth of wavelength channel spacing, and broaden a transmission bandwidth. The circuit uses a multimode waveguide for a connecting part between a field modulation device and an AWG. The field modulation device is constituted by a common input waveguide, an optical branching unit, optical delay lines, a multiplex interference unit, and a mode converter/multiplexer.