Double-Referential Holography and Spatial Quadrature Amplitude Modulation

The wavelength diversity detection (WDD) method for a holographic data storage system (HDSS) actively utilizes scattering from the media to suppress speckle noise with a finite bandwidth light source. In this study, we analytically and numerically revealed signal degradation in the case of a phase-modulation HDSS under WDD in practical conditions, e.g. recording medium position shift; and we proposed an oscillator page recording method to suppress such degradation. Using phase modulation, an oscillator beam must retrieve the recorded phase from interference between the oscillator beam and the reproduced signal beam. The proposed method also records the oscillator beam as a hologram, and simultaneously reproduces the two beams. Simulation results indicate that the proposed method can compensate the degradation and drastically improve the signal-to-noise ratio from 6.5 to 39.1 dB at the largest possible media shift. Therefore, we confirmed feasibility to utilize WDD in PSK under the practical condition.

Section: Proposed Oscillator Page Recording Methodsmentioning

confidence: 99%

Wavelength diversity detection for phase-modulation holographic data storage system

Nakamura

Fujimura

2020

“…8,9) Several techniques to retrieve an amplitude and phase values from the restored complex amplitude image of the data page were proposed and approved experimentally. Coherent detection, 10,11) digital holography, [12][13][14] transport-ofintensity equation decision [15][16][17] and phase-shift embedding 18) are among the most successful.…”

Section: Introductionmentioning

confidence: 99%

Transparency function presentation of computer generated Fourier holograms for complex data page restoration

Zlokazov¹

2019

The present manuscript is dedicated to the development of a holographic data storage (HDS) system based on computer generated Fourier holograms (CGFH). The application of advanced modulation methods such as phase modulation and spatial quadrature amplitude modulation to represent digital data massives as complexly modulated two-dimensional data pages allows one to increase the information capacity of the HDS system. The application of CGFH for storing and reconstructing such data pages is discussed in this article. Particularly, the efficiency of implementation of different light modulation methods that can be used for CGFH transparency function physical realization, such as purely-amplitude, purely phase and combined amplitude and phase, are investigated by means of numeric simulations.

“…As a technique for avoiding the intensity peak of the signal beam, methods using a phase mask, such as a random phase mask, 16) deterministic phase shifter, 17) pseudorandom phase masks, 18) and an optimized phase mask using the Gerchberg-Saxton algorithm, 19,20) have been proposed. In addition, methods in which the data page is represented by the phase modulation 21,22) or the spatial quadrature amplitude modu-lation (SQAM) method 23,24) have been proposed. In these methods using phase modulation, the spatial spectral distribution of the signal beam can be uniform because the phase modulation supplies the high-frequency component to the signal beam.…”

Section: Introductionmentioning

confidence: 99%

Digital image multiplexing/demultiplexing method using spatial spectral diffusion and virtual phase conjugation technique for reduction of dynamic range consumption in holographic medium

Goto

Okamoto

Takabayashi

et al. 2017

Self Cite

The recording density in holographic data storage (HDS) systems is determined by the dynamic range of the recording medium. If a hologram is recorded with a small exposure, the consumption amount of the dynamic range per hologram is reduced, and the recording density can be improved. In this report, we propose a digital image multiplexing/demultiplexing method using spatial spectral diffusion and a virtual phase conjugation technique to reduce the consumption amount of the dynamic range in a recording medium. In our method, multiple signals are simultaneously recorded in a medium by multiplexing those signals using a beam combiner before recording, unlike the general multiplexing method of HDS. Then, each original signal can be reproduced independently by utilizing the property of a random diffuser and a phase-conjugated light. In the simulation, we confirmed that our method can improve the recording density because the consumption of the dynamic range is reduced.