Silicon Photonic Multiplexers Segmented Filtering
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Solution Overview
Problem
Existing optical multiplexers/demultiplexers for silicon-photonic communication networks face challenges in achieving high-density integration due to large size, high insertion loss, and reliability issues, particularly in dense wavelength division multiplexing (DWDM) links, where ring resonator-based devices require significant temperature tuning and coupled-waveguide grating devices are impractical for small bandwidths.
Innovation Solution
An optical multiplexer/demultiplexer system incorporating multiple coupled-waveguide grating devices with band-pass filter characteristics and add/drop filters, including ring resonators and Echelle gratings, that provide coarse and fine optical filtering, with thermally tunable ring resonators and varying grating periods to support multiple optical channels while reducing the number of waveguides and silicon area usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If ring resonators are used to implement add/drop filters in optical multiplexers/demultiplexers, then the device can be made compact, but the free spectral range (FSR) becomes larger than needed and thermal tuning requires hundreds of degrees temperature increase
Solution Approach 1:
The optical filtering function is segmented into two distinct components: coupled-waveguide grating devices provide coarse optical filtering for multiple channels, while ring resonator add/drop filters provide fine optical filtering for individual channels. This segmentation allows each component to operate within its optimal performance range, with the grating device handling the bulk of wavelength selection and the ring resonator providing precise channel isolation.
Solution Approach 2:
The patent changes the operating parameters of the ring resonators by coupling them to grating devices that pre-filter the optical spectrum. This allows the ring resonators to operate with smaller FSR values and reduced temperature tuning ranges, as they only need to provide fine filtering within a narrower bandwidth rather than handling the full spectral range alone.
2Adaptability or versatility
If the radius of ring resonators is decreased to support more optical channels, then the number of channels increases, but bending loss increases and insertion loss increases
Solution Approach 1:
The optical filtering function is segmented into two distinct components: coupled-waveguide grating devices provide coarse optical filtering for multiple channels, while ring resonator add/drop filters provide fine optical filtering for individual channels. This segmentation allows each component to operate within its optimal performance range, with the grating device handling the bulk of wavelength selection and the ring resonator providing precise channel isolation.
Solution Approach 2:
The coupled-waveguide grating devices act as intermediary components that pre-filter the optical spectrum before it reaches the ring resonator add/drop filters. This intermediary filtering reduces the spectral bandwidth that the ring resonators must handle, allowing them to operate with smaller radii while maintaining low insertion loss and acceptable bending loss.
3Area of stationary object
If coupled-waveguide grating devices are used for add/drop filtering, then compactness is achieved, but they have high losses for small bandwidths and are impractical for closely spaced channels
Solution Approach 1:
The optical filtering function is segmented into two distinct components: coupled-waveguide grating devices provide coarse optical filtering for multiple channels, while ring resonator add/drop filters provide fine optical filtering for individual channels. This segmentation allows each component to operate within its optimal performance range, with the grating device handling the bulk of wavelength selection and the ring resonator providing precise channel isolation.
Solution Approach 2:
The patent changes the operating parameters of the ring resonators by coupling them to grating devices that pre-filter the optical spectrum. This allows the ring resonators to operate with smaller FSR values and reduced temperature tuning ranges, as they only need to provide fine filtering within a narrower bandwidth rather than handling the full spectral range alone.
4Measurement precision
If large temperature cycling is applied to tune ultra-compact ring resonators, then alignment with carrier wavelength is achieved, but reliability is adversely impacted
Solution Approach 1:
The optical filtering function is segmented into two distinct components: coupled-waveguide grating devices provide coarse optical filtering for multiple channels, while ring resonator add/drop filters provide fine optical filtering for individual channels. This segmentation allows each component to operate within its optimal performance range, with the grating device handling the bulk of wavelength selection and the ring resonator providing precise channel isolation.
Solution Approach 2:
The patent changes the operating parameters of the ring resonators by coupling them to grating devices that pre-filter the optical spectrum. This allows the ring resonators to operate with smaller FSR values and reduced temperature tuning ranges, as they only need to provide fine filtering within a narrower bandwidth rather than handling the full spectral range alone.
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 compact, high-density optical multiplexing and demultiplexing, improving integration density and reducing silicon area usage, facilitating the scaling of on-chip communication networks while maintaining reliable operation across multiple optical channels.
Implementation Method 1
multiple coupled-waveguide grating devices that optically couple to the bus optical waveguide
Implementation Method 2
A given coupled-waveguide grating device has a band-pass filter characteristic that encompasses multiple optical channels
Implementation Method 3
multiple add/drop filters that optically couple to the coupled-waveguide grating devices. A given add/drop filter has a filter bandwidth corresponding to a given optical channel
Implementation Method 4
thermally tuning such a ring resonator to align the add/drop filter with the carrier wavelength associated with a given optical channel
Implementation Method 5
Dense wavelength division multiplexing (DWDM) is a technology for implementing on-chip optical communication networks
Data Source
AI summary
An optical multiplexer/demultiplexer is described. In this optical multiplexer/demultiplexer, multiple coupled-waveguide grating devices are optically coupled to a bus optical waveguide. A given coupled-waveguide grating device has a band-pass filter characteristic that encompasses multiple optical channels, thereby providing coarse optical filtering. Moreover, the optical multiplexer/demultiplexer includes multiple add/drop filters (such as ring resonators) that optically couple to the coupled-waveguide grating devices. A given add/drop filter has a filter bandwidth corresponding to a given optical channel, thereby providing fine optical filtering. Furthermore, the band-pass filter characteristic of the given coupled-waveguide grating device is approximately equal to or less than a free spectral range (FSR) of the given add/drop filter.