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Network-on-Chip Using Silicon Photonics Waveguide Arrays
Philippe Velha, Nicola Andriolli, Isabella CeruttiScuola Superiore Sant’Anna, Pisa, Italy
Odile Liboiron-LadouceurMcGill University, Montreal, Canada
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Datacom and Computercom Applications
• Optical network-on-Chip (NoC) – networks interconnecting cores, memories, and/or systems– applications: multi/many-core computing systems, embedded
systems, SoC– main requirements and challenges: chip integration, energy
efficiency, low-latency, packaging scalability
Picture from arteris at www.design-reuse.com
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State of the Art
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• Photonic integrated NoCs realized mainly based on optical space switching- switching elements: ring resonators, Mach-Zehnder
interferometers, or semiconductor optical amplifier gates Rather limited flexibility and scalability:
if ports ↗, switching elements ↗↗ footprint ↗, power consumption ↗
• Novel domain for multiplexing and switching: mode• Mode multiplexing and demultiplexing demonstrated in Si
PICs:- possibility of handling the individual modes with good
performance
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Proposed NoC Architecture
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• For scalability, two switching domains:- mode domain- wavelength domain enhance the NoC flexibility,
scalability, parallelism and throughput
• M tiles with N input/output ports each
• In the MN×MN architecture, destination tiles and ports are uniquely identified by wavelengths and modes
• Mode switching is used to select the output tile
• Wavelength switching is used to select the output port
1M
Output Tile 1
Tile M1M
… … Tile 2
Mode switching
Wavelengthswitching
…
……
…Controller/Schedul
er
Input Tile1
Tile 2
Tile M
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P. Velha, I. Cerutti, O. Liboiron-Ladouceur, N. Andriolli, “A Silicon Photonics Network-on-Chip Architecture based on Mode and Wavelength Switching,” Proceedings of Group IV Photonics (GFP), Vancouver, Canada, agosto 2015
WavelengthWavelengthselectorselector
Controller & Controller & SSchedulercheduler
WavelengthWavelengthselectorselector PIC
Tile i
…Tile 1
TX
TX
Tile Mringwaveguide
in port N
RXRX
RXRX
out port 1
out port N
in port 1Tile j
…
Tile k
…
Mode-Wavelength Architecture The Design
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Innovative approachSupermodes instead of Modes
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• Missing component: mode selector• dynamic and flexible selection and de/multiplexing of the modes
• Proposed approach: use of supermodes• different from the set of modes propagating in standard multi-
mode waveguides • advantages:
• larger design flexibility• easier integration of electrical controls (e.g., each waveguide
can be individually tuned)• footprint hardly larger than the size of a standard multi-mode
waveguide
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Conventional multiplexing technique:
space division multiplexing
Optical multiplexing using modes
Novel optical techniques: supermodes
Multi-mode waveguide (MMW)MMW
Array of single-mode waveguides (SMW)SMW
SMW
SMW
Array of coupled single-mode waveguides
CSMWCSMWCSMW
Comparison of Multiplexing Techniques
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Aperiodic array of waveguides
• Si-based fabrication• Fabricated through SiEPIC program in an E-beam run at the
Univ. of Washington on 220nm SOI with single-etch process
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Super-Modes Generated by Parallel, Coupled Waveguides
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simulations spectra measurements
Results obtained on an array of five coupled Si waveguides with a width a [430, 440, 450, 440, 430] nm and a gap of [540, 530, 530, 540] nm
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Mode Selector Arrays of Coupled Single-mode Waveguides
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Results obtained on an array of five coupled Si waveguides with a width a
[430, 440, 450, 440, 430] nm and a gap of
[550, 500, 500, 550] nm φ=πφ=0
φ φ
(a) (b) (c)
Mode 1
Mode 1 Mode 3
Mach-Zehnder configuration with phase shifters capable of inducing a generic shift on each arm [5], to enable the generation of the desired supermode
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Conclusions
• Mode-wavelength architecture has the potential of high scalability, low footprint, low power consumption
• Supermodes are a new domain to explore for switching and multiplexing– high scalability, low crosstalk, limited footprint– easy generation of supermodes– mode switching feasible with phase shifter
• Further investigation is required for developing supermodetheory and components
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Thank you!Emails: [email protected]
This work was supported by MIUR through FIRB project MINOS, by MAE through the high-relevance bilateral project NANO-RODIN