OE-CAM: A Hybrid Opto-Electronic Content Addressable Memory

Yousra Alkabani,Tarek El-Ghazawi,Mario Miscuglio,Volker J Sorger

doi:10.1109/jphot.2020.2966748

Yousra Alkabani, Tarek El-Ghazawi + Show 2 more

Open Access

https://doi.org/10.1109/jphot.2020.2966748

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Abstract

A content addressable memory (CAM) is a type of memory that implements a parallel search engine at its core. A CAM takes as an input a value and outputs the address where this value is stored in case of a match. CAMs are used in a wide range of applications including networking, cashing, neuromorphic associative memories, multimedia, and data analytics. Here, we introduce a novel opto-electronic CAM (OE-CAM) utilizing the integrated silicon photonic platform. In our approach, we explore the performance of an experimental OE-CAM and verify the efficiency of the device at 25 Gbit/s while maintaining the bit integrity under noise conditions. We show that OE-CAM enables a) two orders of magnitude faster search functionality resulting in b) a five orders of magnitude lower power-delay-product compared to CAMs implementations based on other emerging technologies. This remarkable performance potential is achieved by utilizing i) a high parallelism of wavelength-division-multiplexing in the optical domain, combined with ii) 10's of GHz-fast opto-electronic components, packaged in iii) integrated photonics for 10–100's ps-short communication delays. We further verify the upper optical input power limit of this OE-CAM to be given by parasitic nonlinearities inside the silicon waveguides, and the minimal detectable optical power at the back-end photoreceiver's responsivity given channel noise. Such energy-efficient and short-delay OE-CAMs could become a key component of functional photonic-augmented ASICS, co-processors, or smart sensors.

Highlights

A content addressable memory (CAM) is a memory with a search engine at its core used to find values stored within the CAM; upon finding a match it responds with the address where this value is stored
We show that opto-electronic CAM design (OE-CAM) enables a) two orders of magnitude faster search functionality resulting in b) a five orders of magnitude lower power-delay-product compared to CAMs implementations based on other emerging technologies
We focus on the design and evaluation of the optical search engine of OE-CAM

Summary

Introduction

A content addressable memory (CAM) is a memory with a search engine at its core used to find values stored within the CAM; upon finding a match it responds with the address where this value is stored. This search operation is usually executed within one clock-cycle because the CAM search engine is capable of searching all locations in parallel. CAMs are especially useful in different applications that demand short search-return and pattern matching. The output from the search engine is sent to a priority encoder that generates the

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