By Owais AliReviewed by Lexie CornerAug 5 2024Computer storage has evolved significantly from early punched cards to modern cloud storage, with each medium advancing in capacity, cost, and portability. Optical data storage has played a pivotal role in this revolution by offering lower costs per bit, greater storage capacity, and a reliable means of preserving and distributing data.
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Principles of Optical Data Storage
Commercialized in the early 1980s, optical data storage uses lasers to read and write data on reflective discs, utilizing diffraction and interference principles.
When a laser beam is focused on the disc's surface, it interacts with microscopic pits and lands to form binary data patterns. During the reading phase, the laser light reflects off these features, creating a pattern of light and dark spots, which a photodiode then converts into digital data.
However, writing (or burning) data requires a highly intense laser to induce physical or chemical changes in the disc's recording layer, altering light reflection to encode the data.
Modern optical data storage methods include bit-by-bit recording with lasers and holographic storage using interference patterns from split laser beams for higher data densities and faster access times.1,2
Types of Optical Storage Media
Over the years, optical media have evolved into various forms, including laser disc (LD), HD-DVD, and write-once, read-many (WORM) optical cartridges. However, the following three formats have become the leading standards in the optical storage market today.
- Compact Disc (CD): CDs were the first commercial optical storage format, quickly replacing vinyl records and cassette tapes as the preferred medium for audio. Initially, CDs were available only as read-only discs, but soon, recordable and rewritable versions were introduced, allowing for data storage. A CD stores up to 700 MB of data and is read by a low-intensity laser beam while rotating at 200 to 500 RPM speeds.
- Digital Versatile Disc (DVD): DVDs followed CDs as the second major optical storage format. Despite looking similar to CDs, DVDs can store up to 17 GB of data, depending on the format, due to their use of a shorter wavelength red laser,
- Blu-ray Disc: Introduced in 2006, Blu-ray discs represent the current pinnacle of mainstream optical storage technology. They use a blue-violet laser with a wavelength of 405 nm, enabling smaller pits and higher data density for superior audio and video quality. A single-layer Blu-ray disc stores 25 GB, while some variants can hold up to 128 GB of data.
All three formats share the same physical dimensions: 120 mm in diameter and 1.2 mm thick. This standardization allows Blu-ray drives to read DVDs and CDs and DVD drives to read CDs. However, this compatibility does not extend backward.3
Applications of Optical Data Storage
The versatility and reliability of optical data storage have led to its adoption across a wide range of applications.
Entertainment Industry
Optical storage has been pivotal in distributing entertainment media. CDs revolutionized the music industry, offering superior sound quality and durability compared to vinyl records and cassette tapes.
DVDs and Blu-ray discs did the same for the film industry, allowing for high-quality video and audio and additional features like multiple language tracks and bonus content.
Archival Storage
The longevity and stability of optical media make them ideal for long-term data archiving. Libraries, museums, and government agencies value optical storage for its durability and resistance to electromagnetic interference, ensuring that critical data remains intact and accessible for preserving historical, legal, and scientific records.
Software Distribution
Before the widespread adoption of high-speed internet, optical discs were the primary means of distributing software. They offered ample storage for large programs and the ability to include documentation, demos, and additional content.4
Educational and Research Use
Libraries, universities, and research institutions use optical storage to preserve and share large volumes of information. Digital libraries often rely on optical discs for storing and distributing academic journals, theses, and research papers.
Technological Challenges
While optical data storage has achieved considerable success, it faces several challenges in today's digital environment:
- The emergence of cloud storage, high-capacity hard disk drives (HDDs), and solid-state drives (SSDs) has diminished the role of optical storage by offering faster access times, greater convenience, and superior write speeds for frequent data backups and large file transfers.
- Despite their reliable data retention, optical discs are physically fragile and susceptible to damage from scratches or extreme conditions, which can result in data loss.
- Finally, as file sizes for high-resolution video and complex software continue to expand, even the high capacity of Blu-ray discs may fall short for some applications.5
However, ongoing research and development are addressing these challenges and pushing the boundaries of optical storage technology.
Current Research and Emerging Technologies
High Capacity Diamond-Based Optical Storage
A study published in Nature Nanotechnology proposed a novel technique to boost optical data storage capacity using diamonds. This method involves multiplexing data in the spectral domain by encoding information into different color centers within the diamond using lasers of slightly varied wavelengths.
This approach allows data storage at sub-diffraction resolution, supporting high-capacity storage with the ability to write, erase, and rewrite data multiple times.6
Holographic Data Storage Advancements
As cloud data demands high capacity and rapid access, HDDs face performance and capacity limitations. Holographic data storage could replace HDDs, offering high capacity and improved access rates. However, issues like data durability from erasure need addressing.
Recent advancements involve a media and workload-aware energy optimization framework, including optimizing iron (Fe) concentrations in iron-doped lithium niobate and a stretched-exponential erasure model. These improvements have achieved record read counts and density, showing notable gains in energy efficiency and capacity.2
5D Optical Storage
Researchers from The University of Southampton have significantly improved optical data via five-dimensional (5D) data recording using nanostructured glass and femtosecond lasers. This technology encodes data in three spatial dimensions and two birefringence parameters, enabling storage of up to 360 terabytes per disc. It boasts exceptional thermal stability up to 1,000°C and an extraordinary lifespan of 13.8 billion years at 190 °C.
This innovative method offers a highly stable and long-lasting solution for archiving critical information, making it ideal for national archives, museums, and libraries.7
Folio Photonics' 16-Layer Optical Discs
Folio Photonics, a US-based innovator in storage media, has achieved a breakthrough in optical storage, developing the first economically viable enterprise-scale discs with up to 16 layers per side, surpassing the current three-layer limit. Their innovation offers a capacity of 10TB per cartridge, starting at 1TB per disc, with plans to scale to multi-TB capacities.
The discs cost less than $5/TB—five times cheaper than HDDs—and provide 80 % power savings, a 100-year media lifespan, and immunity to electromagnetic pulse (EMP) attacks. This technology addresses current storage solutions' high cost, cyber security risks, and sustainability challenges.8
Optical data storage media has gradually lost popularity in recent years as cloud storage has become a more cost-effective solution for large data volumes. However, it retains niche applications, and recent developments suggest that optical disks may soon regain commercial viability.
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References and Further Reading
- IBM. (2024). Optical storage: A new combination of materials and lasers revolutionized data access and retrieval. [Online] IBM. Available at: https://www.ibm.com/history/optical-storage
- Chu, J., et al. (2024). Can holographic optical storage displace Hard Disk Drives?. Commun Eng. doi.org/10.1038/s44172-024-00225-0
- Sheldon, R. Brown, R. (2021). Optical storage. [Online] Tech Target. Available at: https://www.techtarget.com/searchstorage/definition/optical-storage
- Gu, M., Li, X., Cao, Y. (2014). Optical storage arrays: a perspective for future big data storage. Light: Science & Applications. doi.org/10.1038/lsa.2014.58
- Wagner, K., Pereira, S., Gabriel, C., Bachor, H. (2007). Exploring the limits in Optical Data Storage. Quantum-Atom Optics Downunder. doi.org/10.1364/QAO.2007.QWE11
- Monge, R., Delord, T., Meriles, CA. (2024). Reversible optical data storage below the diffraction limit. Nat. Nanotechnol. doi.org/10.1038/s41565-023-01542-9
- University of Southampton. (2016). Eternal 5D data storage could record the history of humankind. [Online] University of Southampton. Available at: https://www.southampton.ac.uk/news/2016/02/5d-data-storage-update.page
- Gorman N. (2022). Folio Photonics Announces Breakthrough Multi-Layer Optical Disc Storage Technology to Enable Industry-Disruptive Cost, Cybersecurity and Sustainability Benefits. [Online] Foliophotonics. Available at: https://foliophotonics.com/news/folio-photonics-announces-breakthrough-multi-layer-optical-disc-storage-technology-to-enable
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