Coding tradeoffs for high-density holographic data storage

We present an initial experimental evaluation of coding and signal processing tradeoffs in high-density holographic data storage. Block-based and low-pass modulation codes, predistortion of holographic pages during recording (pre-processing), and conventional equalization (post-processing) axe compared using a few recorded holograms. The relative gain in number of stored holograms is obtained by measuring BER as a function of readout power; the effect on density is gauged by the size of the Fourier plane aperture in the holographic system. Results show that equalization provides a 20% density gain, and predistortion a 60% gain. The total improvement in density by combining small apertures with both of these signal processing options is >100% with an 8:12 strong balanced block code, a 6:9 lowpass/sparse code, and a parity thresholding technique with 9.1% overhead.