A Time-Encoded Analog Photonic Interposer for Energy-Efficient Integration of Analog Vision Sensors and Analog Accelerators

By Subhradip Chakraborty ¹ , Zihan Yin ¹, Xuming Chen ², Chengwei Zhou ², Gourav Datta ², and Akhilesh Jaiswal ^1
1 University of Wisconsin–Madison, Madison, WI, USA
² Case Western Reserve University, Madison, WI, USA

Abstract

This work introduces a time-encoded analog photonic interposer that enables long-distance, high-fidelity transport of analog signals between spatially separated chiplets. Unlike prior silicon-photonic links limited to digital data, the interposer preserves analog information by converting amplitudes into timing intervals using an analog-to-time converter (ATC), transmitting them over a wavelength-division-multiplexed photonic link, and reconstructing values at the receiver without an explicit high-precision ADC/DAC data-converter pipeline. The link instead embeds an implicit 6-bit time-domain quantization and uses a single wavelength per processing element independent of bit precision. Evaluated in a fully analog vision pipeline with an in-pixel computing (IPC) sensor, it achieves a 2.04x energy--delay product (EDP) improvement over an 8-bit digital electrical baseline on the 560x560 Visual Wake Words dataset, with the advantage widening with link length even against a precision-matched 6-bit baseline. The pipeline holds 89.87% and 86.15% accuracy on ResNet18 and MobileNetV2 for VWW and generalizes across CIFAR-10 and ModelNet40 within 2% of the digital baseline.

Keywords: 2.5D Integration, Analog Photonic Interposer, Analog Accelerator, In-pixel Computing, Time-domain Computing

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