[OPTICAL REVIEW Vol. 14, No. 4 (2007) 219-223]
© 2007 The Optical Society of Japan

Analysis of Diffuser Shift Margin in Spatial Spread-Spectrum Holographic Multiplexing

Terumasa ITO, Atsushi OKAMOTO, and Kunihiro SATO1

Graduate School of Information Science and Technology, Hokkaido University, Sapporo 060-0814, Japan
1Faculty of Engineering, Hokkai-Gakuen University, Sapporo 064-0926, Japan

(Received February 1, 2007; Accepted April 2, 2007)

We present a novel numerical model for analyzing shift margin in spatial spread-spectrum (SSS) multiplexing, in which the spatial phase of signal beams, not in reference beams, is modulated and demodulated by a random diffuser to multiplex holograms. The shift margin is determined not by the Bragg effect of a thick hologram, but mainly by the phase correlation property of the diffuser used. In our model, we simulate signal data patterns and a smooth rough surface of a diffuser using oversampling and zero-padding, which allows us to cover crosstalk calculations and direct bit-errors calculations, with a fine shift resolution and a wide diffusion angle range. Calculation results revealed that the practical shift margin that ensures a signal to noise ratio more than 3.0 and a bit-error rate less than 10-2 is in the range of 0.3ωeff–0.5ωeff, where ωeff is the effective autocorrelation length of the diffuser transmission function. This model will be helpful in designing the optimum random diffuser profile for SSS multiplexing.

Key words: holographic recording, multiplexing, spatial spread-spectrum, shift margin