16-Bit (4 × 4) Optical Random Access Memory (RAM) Bank

Abstract

During the past years, the limited access-times and memory bandwidth in electronic random-access memory (RAM) has triggered a concerted research effort towards deploying optical memory circuitry for exploiting the inherent high-bandwidth characteristics of light-based technologies. Yet the deployment of optical memory elements in functional optical RAM demonstrations has still been limited to single-bit capacity levels, with the few multi-bit demonstrations still offering only storage functionality without any true random-access capabilities. In this article, we demonstrate an experimental 16-bit all-optical RAM bank prototype that follows a 4 × 4 matrix organization and supports addressable random access storage of four 4-bit WDM-formatted optical Data Words at a 20 Gb/s memory-throughput. The proposed architecture constitutes of completely passive Row/Column decoding (RD/CD) subsystems, four Semiconductor Optical Amplifier Mach-Zehnder Interferometer (SOA-MZI) Access Gates (AGs) for enabling the access towards the 4 available Word Lines (WLs) and 16 all-optical Flip-Flops (AOFF) arranged in a 4 × 4 RAM bank. Each FF is incorporated in an indicative photonic integrated circuit (PIC). The experimental validation of the complete 16-bit RAM bank reveals error-free operation in Write mode with a peak power penalty between 8.3–10.2 dB at 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−9</sup> bit-error-rate (BER) measurements, indicating a roadmap for two-dimensional addressable (2D) RAM banks that can penetrate the optical computing application domain.