Fault tolerance of a dynamic 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 particularly 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 perfectly parallel programmable capability of ORGAs enables perfect avoidance of those defective areas through alternative use of other non-defective areas. Moreover, holographic memories to store contexts are known to have high defect tolerance because each bit of a reconfiguration context can be generated from the entire holographic memory. For those reasons, the damage of some part of the device rarely affects its diffraction pattern or a reconfiguration context. Consequently, ORGAs are very 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 experimental results of defect tolerance of a new dynamic optically reconfigurable gate array with a one-time easily writable holographic memory.