Defect Tolerance of an Optically Reconfigurable Gate Array with a One-time Writable Volume Holographic Memory

Optically reconfigurable gate arrays (ORGAs) have been developed as a type of multi-context field programmable gate array to realize fast reconfiguration and numerous reconfiguration contexts. Along with such advantages, ORGAs have high defect tolerance. They consist simply of a holographic memory, a laser diode array, and a gate array VLSI. Even if a gate array VLSI includes defective areas, the ORGAs capability of perfectly parallel programmability enables avoidance of those defective areas through alternative use of other non-defective areas. Moreover, a holographic memory to store contexts is known to have high defect tolerance because each bit of a reconfiguration context can be generated from the entire holographic memory.Consequently, damage of a holographic memory rarely affects its diffraction pattern or a reconfiguration context. For that reason, ORGAs are extremely robust against component defects in devices such as a laser array, a gate array, and a holographic memory, and are particularly useful for space applications, which require high reliability.This paper presents experimentation related to the defect tolerance of new optically reconfigurable gate array with a one-time easily writable volume holographic memory.