32 channel WDM filter for optical interconnect
imec in Belgium has developed a 32 channel wavelength-division multiplexing (WDM) filter in silicon.
The WDM filter developed by imec is four times the capacity of today’s commercial transceivers and supports the continued scaling of the bandwidth density and power efficiency of next-generation silicon-photonics-based transceivers. This is key for the expansion of short-reach optical interconnects in high-performance AI/ML compute clusters.
The design has low optical insertion losses of 2dB and crosstalk levels better than 16dB are maintained, even at this high channel count. The silicon substrate undercut process and an optimized heater in the silicon boosts the thermo-optic tuning efficiency to 290GHz/mW.
Silicon photonics is a key technology platform for cost-effective integration of terabit scale transceivers, but there are challenges in bandwidth density, power efficiency and latency in AI/ML system interconnect. Scaling up link bandwidth by adding more wavelength channels is typically associated with significant optical losses and excessive tuning power when using silicon-integrated components.
- imec shows co-integration of SiN waveguides and active silicon
- £11m silicon photonics centre for Southampton
The silicon patterning in imec’s 300mm Silicon Photonics platform (iSiPP300) helps implement the ring resonator and interleaver components for the WDM filter with 32 wavelengths at 100GHz channel spacing in the O-band, matching the specifications of the CW-WDM multi-source agreement (MSA) for data centre equipment suppliers.
“imec’s optical I/O R&D program aims at disruptive scaling of both bandwidth density and power consumption of silicon-integrated optical interconnects, which often present conflicting requirements,” said Joris Van Campenhout, fellow and R&D programme director at imec.
“Our 32-channel WDM filter enables Tbps-scale aggregate bandwidth per optical fibre using individual lane rates of only 32Gbps, enabling error-free link operation without power-hungry digital signal processing. The compact footprint, low optical losses, and high wavelength tuning efficiency opens a pathway to Tbps/mm-scale optical interconnects with overall power
efficiencies of just 1pJ/bit.”
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