Dennis Gabor's groundbreaking contributions in the 1 940 s initially illuminated the enigmatic and potentially boundless field of holography. Over the subsequent decades, through his relentless perseverance, he continuously deepened and refined the theoretical framework of this technology. Holography, once perhaps confined to the realm of scientific fancy, gradually evolved into a pivotal tool for exploring new horizons in information storage, led by Gabor's visionary guidance. As the 1960s dawned, the rapid advancement of science and technology paved the way for Van Heerden, who, with his prescient vision, boldly foresaw the vast potential applications of holographic technology in data storage. This idea, akin to a seed, swiftly germinated and flourished with the nourishment provided by laser technology. The emergence of lasers furnished the crucial light source necessary for holographic data storage technology, thereby transitioning holographic data storage from theoretical discourse to practical implementation and gradually positioning it as a shining star in the landscape of next-generation optical storage.The unique advantage of holographic optical data storage resides in its unprecedented capacity to store information in a three-dimensional space within the recording medium. This distinctive feature allows for the parallel writing and reading of data, in stark contrast to traditional two-dimensional data transmission methods. By adopting this three-dimensional storage approach, holographic data storage technology not only vastly enhances storage capacity but also markedly boosts data transmission speed. Consequently, holographic data storage demonstrates unparalleled superiority in addressing the challenges posed by the big data era. The core of holographic data storage technology hinges on the volumetric recording of spatial light wave distributions, ushering in an entirely novel mode of data page storage. Leveraging the selective properties of thick holograms, holographic data storage facilitates parallel data processing and multiple recordings within the same medium area, resulting in faster data transmission rates and higher storage densities. This technology not only transcends the confines of traditional optical disc storage but also pioneers new avenues in the realm of data storage.To date, the domain of holographic data storage has delved into a variety of devices and technical solutions, with off-axis and coaxial systems emerging as the two most central system architectures. Furthermore, technologies rooted in computer-generated hologram and self-referencing have sequentially emerged, providing fresh momentum to the advancement of holographic data storage technology. As research continues to deepen, holographic data storage technology has made significant progress in multiple dimensions, including data recording density, data transmission rate, data storage security, environmental tolerance, and rewritable media. To further enhance the recording density of holographic data storage, researchers have proposed various innovative methods, among which multiplexing technology is key to achieving high storage density.Volume holographic data storage technology, leveraging the Bragg selectivity of volume holographic gratings, enables the storage of multiple sets of data at the same location within the storage medium, with each data page being individually readable. The implementation of this technology hinges on two primary categories of methods: spatial multiplexing and orthogonal/incoherent multiplexing. Spatial multiplexing techniques, specifically angle multiplexing and shift multiplexing, accomplish multi-address storage of information by adjusting either the angle or the relative position between the reference light and the object light. This approach effectively harnesses the storage volume, ultimately enhancing storage density and efficiency. To address the significant crosstalk noise issue in spatial multiplexing technology, researchers have introduced orthogonal/non-correlated coding multiplexing strategies for reference light. This strategy, based on the fundamental physical properties of light waves, has promoted the development of amplitude coding, phase coding, and polarization coding multiplexing technologies. By adjusting the pattern parameters of the reference light, multiple holograms can be stored in a superimposed manner, and through carefully designed grating superposition, only a specific diffraction efficiency is maximized, thereby effectively reducing crosstalk noise and enhancing the storage efficiency of the system.It is noteworthy that these multiplexing technologies do not exist in isolation but can be integrated and applied together to further promote the increase in storage density. When combined with multi-dimensional modulated data information, holographic data storage technology is expected to achieve unprecedented storage densities. Looking ahead, with the continuous progress of materials science, optical engineering, and information technology, holographic data storage multiplexing technology will continue to make new breakthroughs and contribute more to the informatization process of human society. Beyond the traditional application field of data storage, holographic multiplexing technology also exhibits broad application prospects in areas such as three-dimensional display, augmented reality, and optical communications. These emerging applications will not only further enrich the connotation of holographic data storage technology but also inject new vitality into the development of the world economy. Therefore, we have reason to believe that holographic multiplexing technology will play an increasingly important role in the future, becoming an important force in driving scientific and technological progress and economic development.