Researchers investigate holographic memory error rates

Researchers investigate holographic memory error rates

Among the papers at CLEO `96 reporting advances in holographic data storage was one from Michael Jefferson of the IBM Almaden Research Center (San Jose, CA) that discussed error studies in such systems. The IBM team evaluated materials and technologies at densities comparable to product-level storage, u¥to 1 megapixel/data page, instead of a proof-of-principal system with densities too low to evaluate material effects and system deficiencies. Jefferson stressed that the high data rates involved with holographic storage preclude using digital signal processing to achieve acceptable bit-error rates by correcting for system deficiencies. Errors arise from components, system integration, and the storage medium itself, which is the largest error generator.

Thermal fixing for nonvolatile holographic storage was described by J. F. Heanue of Optitek (Mountain View, CA). Data recorded in an iron-doped lithium niobate crystal are fixed by post-recording heating; both recording and readout occur at room temperature. An alternative, photorefractive-based recording, is susceptible to erasure upon readout because the electrons remain optically excitable. Compact, high-resolution holographic storage systems were addressed by Accuwave (Santa Monica, CA) researchers who use phase-conjugate holograms without any lenses, reducing system size and simplifying architecture.