Coding applications in volume holographic memory systems

Abstract

Volume holographic memory (VHM) systems are page-oriented optical data storage systems with a relatively large storage capacity, a high aggregate data transfer rate, and a fast access time as compared with other conventional mass data storage systems. In addition to the noise sources commonly present in a conventional communication channel, the VHM systems use a two-dimensional (2-D) data format and therefore suffers from 2-D electrical/optical hybrid noises. In this dissertation, we apply digital communication coding techniques to such a page-oriented optical memory system. To establish a coding performance baseline, we take an information theoretical perspective to study the design of 4F optical imaging systems, and the storage capacity of page-wise accessed VHM systems. In addition to the information-based figure of merit, bit-error rate (BER) serves as a more practical data fidelity measure. A BER-based optical design and a constant BER recording schedule in VHM systems are shown to support the coding analyses based on the BER metric. We analyze the VHM storage capacity while applying Reed-Solomon error-correction coding (ECC) and demonstrate that the use of the 2-D interleaving together with ECC results in a significant capacity improvement in the presence of systematic errors. In addition, soft-decision iterative decoding affords us a 2-D parallel decoding scheme that unifies the 2-D page equalization and decoding. A highly parallel decoder is discussed in the context of the 2-D low-pass channel mitigation and error correction. In the last part of this dissertation, we consider hardware implementation issues in 2-D optical systems. We design two coding related components using the MOSIS Orbit 2 mum n-well process to fabricate two CMOS VLSI chips. Power consumption and aerial scaling laws are discussed for each applications.