Optical Interconnects for Chip Multiprocessor Architectures

Chip multiprocessor architectures face mounting pressure to sustain ever-increasing data bandwidths while containing power consumption and latency. Traditional copper interconnects encounter fundamental limitations in signal attenuation, crosstalk and clock skew as link densities rise. Optical interconnects promise to alleviate these bottlenecks by exploiting low-loss silicon photonic waveguides, wavelength division multiplexing and compact switching elements to deliver multi-terabit per second channels across die or between chiplets. Key enabling components include microring resonators and Mach–Zehnder interferometers for modulation and switching, heterogeneous integration of III–V light sources and germanium photodetectors for emission and reception, and optical phased arrays for flexible free-space links within multilayer substrates. Architectures based on photonic networks-on-chip combine non-blocking optical routers with intelligent wavelength routing to orchestrate traffic among cores, memory banks and specialised accelerators. The adoption of optical interconnect fabrics offers reduced latency, enhanced energy per bit and immunity to electromagnetic interference, fostering scalable heterogeneous computing systems in data centres, high-performance computing clusters and emerging chiplet ecosystems.

Research from Nature Portfolio

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Research from all publishers

Recent studies have demonstrated on-chip optical wireless switches based on thin-film lithium niobate on insulator, using reconfigurable optical phased arrays at both transmitter and receiver ends. These devices exploit compact LN-based antenna elements and phased-array beam steering to establish dynamic point-to-point links with multi-gigahertz bandwidth, while tolerating fabrication imperfections and optimising geometric parameters for minimal loss.

Design frameworks for optical wireless interconnections in 2.5 D manycore systems have leveraged integrated optical phased arrays to create reconfigurable N×N switching matrices. Three-dimensional simulations reveal how in-plane taper antennas can route signals across a multilayer silicon interposer, accounting for multipath propagation and enabling high-bandwidth, low-latency chiplet communication without physical waveguide crossings.

Complementary work on fully integrated optical wireless network-on-chip architectures has proposed 3×3 switching matrices that combine phased-array beamforming with on-chip multilayer modelling. This approach achieves reconfigurable connectivity among multiple nodes with bit rates exceeding 10 Gb/s, demonstrating tolerance to cladding-layer variations and offering a path to scalable, energy-efficient photonic fabrics for future multicore processors.

Optical Interconnects for Chip Multiprocessor Architectures publication trend

The graph below shows the total number of articles in optical interconnects for chip multiprocessor architectures across all publications each year (not limited to Nature Index journals).

Technical terms

Optical interconnect: A data link that transmits information by modulating light within waveguides or free-space paths, offering higher bandwidth and lower loss than electrical conductors.

Silicon photonics: The integration of photonic components—waveguides, modulators, detectors—on a silicon substrate, using CMOS-compatible fabrication for large-scale manufacturing.

Optical phased array (OPA): An assembly of individually controlled optical emitters whose relative phase shifts steer a light beam electronically, enabling reconfigurable free-space links.

Microring resonator: A ring-shaped waveguide that supports resonant optical modes, used for filtering, modulation and switching by tuning its refractive index or geometry.

Network-on-chip (NoC): A scalable on-chip communication architecture that interconnects cores or modules via a packet-switched network fabric, here implemented with photonic switches and waveguides.

Wavelength division multiplexing (WDM): A technique that multiplexes multiple data channels onto different optical wavelengths on a single waveguide to increase aggregate throughput.

References

1. LNOI Wireless Switches Based on Optical Phased Arrays for On-Chip Communication. IEEE Journal on Selected Areas in Communications (2024).
2. Design of reconfigurable on-chip wireless interconnections through Optical Phased Arrays.. Optics Express (2021).
3. Reconfigurable Optical Wireless Switches for On-Chip Interconnection. IEEE Journal of Quantum Electronics (2022).