Tawei Ho

Least square equalization and variable thresholding for 3D page-oriented optical data storage systems

We describe equalization and detection techniques that overcome both inter-page interference (IPI) and intersymbol interference (ISI) in volumetric (3D) page-oriented optical data storage (PODS) systems.

Iterative detection for interpage interference in imaging page-oriented optical data storage

Page-oriented optical data storage (PODS) has advantages in data transfer rate and storage capacity over planar type data storage. The increase in capacity comes from the use of the third spatial dimension and increased packing density from reduced pixel pitch and inter-page spacing. We present a low complexity iterative detection procedure that combats inter-page interference (IPI) and intersymbol interference (ISI) while maintaining acceptable bit error rate performance.

Variable threshold detection for 3D page-oriented optical data storage systems

We propose a new method to determine dynamically the threshold in volumetric (3D) page-oriented optical data storage (PODS) systems that use an incoherent (non-holographic) imaging format. In these systems, the inter-symbol interference (ISI) and inter-page interference (IPI) that occurs with very high data packing density are two major sources of error during data retrieval. Traditional readout systems based on a fixed binary decision threshold provide poor results. Our variable threshold detection method identifies the amount of interference from three dimensions for each data element (pixel) and adjusts the threshold value based on that information. In simulation results, the variable threshold method exhibits significant improvement over traditional detection methods.

Iterative detection for imaging page-oriented optical data storage systems

Imaging page-oriented optical data storage, with its high bit packing density and many parallel readout channels, offers a solution for high capacity data storage with fast data transfer rate. As in any data storage system, increasing the packing density increases the effect of inter-symbol interference (ISI) and inter-page interference (IPI). We describe a combination of modulation encoding/decoding and error correction that overcomes this interference allowing high packing density in the presence of noise while maintaining acceptable bit error rate (BER). We also describe an extension of the algorithm to multi-level (grayscale) encoding.

Variable Threshold and Fixed-Point Arithmetic Least Square Equalization in Page-Oriented Optical Data Storage

We describe significant improvements from novel variable threshold and fixed-point arithmetic least square equalization modulation detection for volumetric (3D) page-oriented optical data storage (PODS) systems with extreme intersymbol interference (ISI) and interpage interference (IPI).

Multi-Level Encoding and Detection for Imaging Page-Oriented Optical Data Storage

Imaging page-oriented optical data storage can record data bits in grayscale, with potential total capacity benefits. We describe an extension of our binary iterative decision feedback modulation detection technique to multi-level operation.

Least square equalization for multi-level 3D page-oriented optical data storage systems

We describe non-adaptive and adaptive least square equalization and detection techniques for two-level and multi-level volumetric (3D) page-oriented optical data storage (PODS) systems. The procedures overcome the effects of noise and both inter-page interference (IPI) and intersymbol interference (ISI) to reduce system bit-error-rate (BER).

Iterative decision feedback processing for 3D imaging page-oriented optical data storage

We describe iterative decision feedback 3D signal processing techniques that overcome inter-page interference (IPI) and inter-symbol interference (ISI) in imaging page-oriented optical data storage systems. We compare their performance with alternative equalization and maximum-likelihood detection, describe resulting capacity improvements, and extensions to multi-level systems.

Flip-chip bonded optoelectronic integration based on ultrathin silicon (UTSi) CMOS

We describe the design and test of flip-chip bonded optoelectronic CMOS devices based on Peregrine Semiconductors 0.5 micron Ultra-Thin Silicon on sapphire (UTSi) technology. The UTSi process eliminates the substrate leakage that typically results in crosstalk and reduces parasitic capacitance to the substrate, providing many benefits compared to bulk silicon CMOS. The low-loss synthetic sapphire substrate is optically transparent and has a coefficient of thermal expansion suitable for flip-chip bonding of vertical cavity surface emitting lasers (VCSELs) and detectors. We have designed two different UTSi CMOS chips. One contains a flip-chip bonded 1 x 4 photodiode array, a receiver array, a double edge triggered D-flip flop-based 2047-pattern pseudo random bit stream (PRBS) generator and a quadrature-phase LC-voltage controlled oscillator (VCO). The other chip contains a flip-chip bonded 1 x 4 VCSEL array, a driver array based on high-speed low-voltage differential signals (LVDS) and a full-balanced differential LC-VCO. Each VCSEL driver and receiver has individual input and bias voltage adjustments. Each UTSi chip is mounted on different printed circuit boards (PCBs) which have holes with about 1 mm radius for optical output and input paths through the sapphire substrate. We discuss preliminary testing of these chips.