Two-Dimensional Optical Storage: High-Speed Read-Out of a 50 GByte Single-Layer Optical Disc with a 2D Format Using λ=405 nm and NA=0.85

Abstract

With ever increasing storage capacities, long read-out times of content are becoming a bottleneck for the convenient use of optical storage devices. Two-dimensional optical storage (TwoDOS) is a new concept that solves this data-rate problem through parallel read-out. Furthermore, an increase of at least a factor of 2 in storage capacity is achieved by exploiting a two-dimensional format. The advantages offered by TwoDOS are obtained without the need of changing the physics of the read-out system. Using Blu-ray Disc optics, single-layered 12 cm discs with capacities up to 50 GByte have been read out successfully. Signal level and error analysis show the feasibility of a further capacity increase. Also, bit-rates as high as 700 Mbit/s during read-out have been reached. All this is achieved by applying advanced signal processing and advanced disc mastering techniques and the proper design of the optical path.

Minimum-Latency Tracking of Rapid Variations in Two-Dimensional Storage Systems

“…For first-order loops the loop filter has transfer function , where is the total gain of the loop. The mismatch transfer function is evaluated to be (1) Let be a unit step function. Then, for , the mismatch can be approximated as an exponentially decaying function , where is the time constant of the loop expressed in sampling intervals.…”

“…7, a parameter-domain model of the minimum-latency first-order adaptation loops is shown together with the assumed parameter model. 1 The input-referred noises and are inputs of the model and are uncorrelated. Furthermore, a delay of bits is present in the inner loop to mimic the large detection delay of the inner row.…”

“…TEADILY increasing storage densities are a clear trend in storage systems [1]. Reduced margins (e.g., margins with respect to disc tilt, signal-to-noise ratio, SNR) and increased sensitivity to piece-wise and temporal variations of physical storage channel parameters are consequences of this trend and necessitate an increasing amount and an increasing accuracy of adaptivity (e.g., timing recovery, automatic gain control, and other adaptive loops) in the data receiver [2] [4].…”

Pushing the limits of optical storage

“…In both cases, perfect synchronization between the bit-rows is essential. We use parallel beams and a partitioned photo-detector to read the data from the disc 3,4 . These multiple beams are generated from a single laser, by a specially designed diffraction grating.…”

“…In our first studies, we used hexagonal Near Field patterns of data pits, but later we also obtained good results with d=1 run-length-limited codes. With this method we were able to reach data capacities up to 2 times the capacity in single-layer, 1-dimensionally coded BD discs (50 GB) 4 . The maximum data rate that we obtained experimentally is 700 Mbps.…”