Angle/fractal multiplexing using x-y Galvano mirror system and new method of improving random-access performance

Angle/fractal multiplexing using an x-y Galvano mirror and a new method of improving random access for a holographic digital data storage (HDDS) are discussed in this paper. Using angle/fractal multiplexing, total 1000 data pages were recorded on a 0.03% Fe-doped LiNbO₃ crystal. In this process, we introduced a random-access concept in a HDDS and proposed a new method to improve the random-access performance. The proposed method is the use of an additional signal beam to record a page count signal, and a basic experiment was performed to verify the idea. A 2 × 10^-4 raw bit error rate (BER) was achieved from the recorded data, and the effectiveness of the proposed page count signal during seek motion was proved by experiments. Finally, a random-access using a proportional-integration-derivative (PID) controller combining with a Kalman filter to estimate the precision of the output was carried out, and some comments on the results were presented.