Bringing WDM Into Optical Static RAM Architectures

TLDR

Optical RAM offers a light‑based alternative to overcome the electronics memory wall, enabling picosecond‑scale access times. The study introduces wavelength‑division multiplexing (WDM) principles into optical RAM storage to provide new architectural perspectives. The architecture uses a 4×4 WDM optical RAM bank with a SOA‑based multi‑wavelength Access Gate and dual‑wavelength SOA‑based All‑Optical Flip Flops, enabling simultaneous random access to a 4‑bit word encoded across eight wavelengths. The design achieves 10 Gbit/s throughput with 15 mW/Gbit/s for the Access Gate and 120 mW/Gbit/s for the flip‑flops, demonstrating that WDM‑enabled optical RAM can simplify circuitry, reduce power, and allow reconfigurable optical cache mapping.

Abstract

Optical RAM appears to be the alternative approach towards overcoming the "Memory Wall" of electronics, suggesting use of light in RAM architectures to enable ps-regime memory access times. In this communication we take advantage of the wavelength properties of optical signals to present new architectural perspectives in optical RAM structures by introducing the WDM principles in the storage area. To this end, we report on a 4 × 4 WDM optical RAM bank architecture that exploits a novel SOA-based multi-wavelength Access Gate (WDM-AG) and a dual wavelength SOA-based SET-RESET All-Optical Flip Flop (AOFF) as fundamental building blocks. The WDM-AG enables simultaneous random access to a 4-bit optical word encoded in 8 different wavelengths, allowing for the four AOFFs of each RAM row to effectively share the same Access Gate. The scheme is shown to support a 10 Gbit/s operation for the incoming 4-bit data streams, with a power consumption of 15 mW/Gbit/s for the WDM-AG and 120 mW/Gbit/s for the AOFFs. The proposed optical RAM architecture reveals that exploiting the WDM capabilities of optical components can lead to RAM bank implementations with smarter column/row encoders/decoders, increased circuit simplicity, reduced number of active elements and associated power consumption, while enabling for re-configurability in optical cache mapping.