Multiresolution Coding Using Amplitude and Phase Modulations for Holographic Data Storage

Abstract

A new data coding method using both amplitude and phase modulations is proposed for increasing the coding rate in a holographic memory. The phase modulation code has a lower resolution than the conventional sparse block code used as the amplitude modulation code. The phase modulation code can add more than 1 bit to the amplitude modulation code. We show that the coding rate can be increased up to 0.78 from 0.67 in the 3:9 amplitude modulation code when the binary phase code is added. We also show that the bit error rate and signal-to-noise ratio in the amplitude data are improved by adding the phase modulation code in speckle shift multiplexing. The histogram of the phase distribution is also separated well.