Experimental evaluation of user capacity in holographic data-storage systems

Area of Science:

• Optical data storage
• Information theory
• Materials science

Background:

• Holographic storage systems face challenges in maximizing data density while maintaining signal integrity.
• Conventional recording schedules often prioritize diffraction efficiency, potentially compromising raw bit-error rate (BER).

Purpose of the Study:

• To develop and experimentally validate a procedure for estimating the capacity of holographic storage systems based on raw BER.
• To investigate the impact of modulation and error-correction coding on storage capacity and identify optimal system parameters.

Main Methods:

• An experimental procedure was established to correlate the number of stored holograms with the raw BER.
• Capacity scaling was analyzed against raw BER, incorporating modulation codes and thresholding techniques.
• Experiments were conducted using Lithium Niobate (LiNbO3) in a 90-degree geometry.

Main Results:

• Scheduling recording exposures for a uniform raw BER improves storage capacity compared to equalizing diffraction efficiency.
• Error-correction coding increases the number of storable holograms but introduces a capacity cost per hologram due to redundancy.
• A trade-off between coding redundancy and capacity cost was quantified, identifying an optimal operating point.

Conclusions:

• The developed experimental procedure enables realistic comparison of system choices for holographic storage.
• Optimizing recording schedules for uniform raw BER is crucial for enhancing holographic storage capacity.
• The study quantifies the trade-offs associated with error-correction coding, guiding the design of efficient holographic storage systems.