Orthogonal reference pattern multiplexing for collinear holographic data storage

An orthogonal reference pattern multiplexing (ORPM) method for collinear holographic data storage (CHDS) is investigated to increase the data storage density and realize parallel optical image superimposition. Holograms are multiplexed in the same volume of the recording medium with multiple orthogonal reference patterns (RPs). The physical principle of this method is analyzed based on scalar diffraction theory. The orthogonal condition of the RPs is derived in order to suppress the interpage cross talk. The parameters of the radial-line RP have significant influence on the signal-to-noise ratio (SNR) of the reconstructed data page. They are optimized to reduce the intrapage cross talk. With a random binary phase mask (RBPM) located closely before the spatial light modulator, SNR of the reconstructed data page is seven times the SNR without the RBPM. Three data pages are multiplexed in the same volume of the medium using the ORPM method. The reconstructed data pages for the CHDS system show the effectiveness of the RBPM in suppressing the intrapage and interpage cross talk.