Imec demonstrates compact 32-channel silicon-based wavelength filter with low loss and high tuning efficiency

Mar 25, 2024 | Press

LEUVEN (Belgium), March 25, 2024 — This week, in a top-scored paper at the OFC Conference (San Diego), imec, a world-leading research and innovation hub in nanoelectronics and digital technologies, is presenting a major advancement in silicon-based wavelength-division multiplexing (WDM) capability. A compact 32-channel silicon-based wavelength filter is demonstrated for the first time with low loss and high tuning efficiency, enabling a 4x increase in the number of transmitted and received wavelength channels compared to today’s commercial transceivers. The demonstrated capability will enable continued scaling of the bandwidth density and power efficiency of next-generation silicon-photonics-based transceivers, addressing the requirements for short-reach optical interconnects in high-performance AI/ML compute clusters.    

Continued scaling of optical interconnects is essential for achieving further performance and efficiency gains in AI/ML compute clusters. Silicon photonics is a key technology platform for cost-effective integration of Tbps-scale transceivers, but the demanding requirements for bandwidth density, power efficiency, and latency in AI/ML system interconnects require substantial improvements at the process, device, and circuit level. For example, 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.

By combining the advanced Si patterning capability in imec’s 300mm silicon photonics platform (iSiPP300) with innovative and highly optimized designs of Si ring resonator and interleaver components, imec has overcome these challenges, realizing a WDM filter with 32 wavelengths at 100GHz channel spacing in the O-band, matching the specifications of the CW-WDM multi-source agreement (MSA). Owing to the careful design optimization, low optical insertion losses of about 2dB and crosstalk levels better than 16dB are maintained, even at this high channel count. By leveraging imec’s local Si substrate undercut process and optimized heater designs, the thermo-optic tuning efficiency is among the best-reported values at 290GHz/mW. 

Joris Van Campenhout, fellow and R&D program director at imec: “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. Our new 32-channel WDM filter enables Tbps-scale aggregate bandwidth per optical fiber using individual lane rates of only 32Gbps, enabling error-free link operation without power-hungry digital signal processing. Leveraging its compact footprint, low optical losses, and high wavelength tuning efficiency, the demonstrated WDM filter opens a pathway to Tbps/mm-scale optical interconnects with overall power efficiencies of just 1pJ/bit.”

About imec

Imec is a world-leading research and innovation center in nanoelectronics and digital technologies. Imec leverages its state-of-the-art R&D infrastructure and its team of more than 5,500 employees and top researchers, for R&D in advanced semiconductor and system scaling, silicon photonics, artificial intelligence, beyond 5G communications and sensing technologies, and in application domains such as health and life sciences, mobility, industry 4.0, agrofood, smart cities, sustainable energy, education, … Imec unites world-industry leaders across the semiconductor value chain, Flanders-based and international tech, pharma, medical and ICT companies, start-ups, and academia and knowledge centers. Imec is headquartered in Leuven (Belgium), and has research sites across Belgium, in the Netherlands and the USA, and representation in 3 continents. In 2022, imec’s revenue (P&L) totaled 846 million euro.

Further information on imec can be found at