Digital holographic data storage systems currently under development have Terabit storage capacity, as is necessary for the next generation of huge entertainment and business databases. However, even at Gbit/second transfer rates, each search of such a database for a particular item will take a minimum of a quarter of an hour of dedicated, high-speed computing time. In contrast, an all-optical search can be performed in milliseconds, independent of the size of the database. This proposal presents a design which is capable of complex searches of a Gbit of holographically sotred digital data in a msec. While the properties of image-based (analog) volume holographic correlators are known, associative search/correlation of digital folume holographic data present unique problems and opportunities because of the spatially-varying digital data encoding. The choice of optical impmlementation, digital channel encoding, error-correction technique, and data page layout all effect the bit-error-rate, cross correlation suppression, level of association and generalization, and degree and type of shift-invariance of the search engine. The design presented in this proposal maximizes digital search capabilities, and can be added to holographic memory architectures at extremely low additional cost.
Keywords: Low Cost, Volume Correlator, Holographic Memory, Associative Memory