Computer - Optical Storage (Discs)

What are Optical Storage (Discs)?

Optical discs are a common method of storing huge amounts of data due to their large storage capacity and durability. Optical discs read and write data using laser beam. The optical storage technology has been widely employed to large quantity data like storing music, movies, games, and computer software.

Optical-storage technology uses a laser beam to imprint digital data onto an optical disc by creating small indentations in a spiral pattern on the disk's surface. A low-power laser scanner is employed to "interpret" these indentations, where changes in the brightness of reflected light from the indentations are transformed into electrical signals. This technology is used in to design compact disc, which is capable of recording sound; the CD-ROM, which can store text, images, and sound; the WORM (write-once read-many) disc, which allows for one-time writing and multiple readings; and newer discs that offer complete rewritability. Overall, they are flat, circular polycarbonate discs with a reflective data layer and a protective outer layer.

Characteristics of Optical Storage Systems

Some of the key Characteristics or features and properties of Optical Storage Systems are as follows −

• High Storage Capacity − Optical storage has large storage capacity; CDs, DVDs, and Blu-ray discs has high storage capacity.
• Performance − The performance of Optical storage devices are up to mark as they deliver fast data transfer rates, less access time and high-speed buffering.
• Efficient reading and writing of data − Optical storage has efficient reading and writing of data.
• Durability and Reliability − The architectural design of optical storage devices reduces risk of damage or data corruption due to surface scratches, dust, and fingerprints. These features make it durable and reliable.
• Error correction − Optical media reading technology uses error correcting techniques like Reed-Solomon and Cross-Interleaved Reed-Solomon Error correcting to ensure data integrity.

Types of Optical Storage

Some of the common types of Optical Storage are as follows −

1. CD (Compact Disc)

The Optical Storage CDs were introduced in the early 1980s. In optical storage technology; CDs were introduced first. They can hold up to 700 megabytes of data and are commonly used for music, software, and data storage.

2. DVD (Digital Versatile Disc)

DVDs are extended version of CDs; they can have significantly more storage capacity like 4.7 GB single-layer and 8.5 GB dual-layers. This optical storage is most widely used in movie production, software distribution, and data backup.

3. Blu-ray Disc

Blu-ray is an advance optical discs storage method. A Blu-ray, may hold more data than DVDs. Standard discs can carry 25 GB (single-layer) or 50 GB (dual-layer), with larger capacities for specialised variants. Blu-ray discs are used for both HD video and data storage.

4. Archival Disc

Archival optical discs keep data for a long time. They are ideal for archiving data due to their large volume and longevity.

How Optical Discs work?

Optical discs work by using a laser to read and write data. Its working depends on the structure of an optical disc. The layered architecture includes −

• Label − A layer that can contain either printed text or images.
• Polycarbonate layer − A transparent overlay containing the actual data.
• Reflective layer − A thin coating of material that reflects laser light back onto the laser diode.
• Protective layer − A clear layer that shields the reflective layer from damage.
• Recording Mechanism − Lasers leave tiny pits and lands on CDs, DVDs, and Blu-rays. Pits and lands represent binary data.
• Reading Mechanism − The laser of the disc drive detects the reflections of pits and lands in order to read data. Drive translates reflections into digital data.

A less powerful laser is used to extract digital data from the designs on the reflecting layer. To write data, a more powerful laser burns a small portion of the reflecting layer, creating pits and bumps that represent binary data. Optical discs, a common form of data storage and video distribution, are increasingly competing with other storage technologies such as USB drives, external hard drives, and cloud storage. However, they are still employed in some cases where longevity, the capacity to keep data even when the machine is turned off, and resistance to data corruption are critical.

Advantages of Optical Storage

Some of the key advantages of Optical Storage are as follows −

• Durability − The lifespan of optical storage media is quite long which makes its durable.
• Environmental resistance − Optical discs are resistant to certain environmental variables, such as humidity and temperature. This increases their durability and stability.
• Error correction − Optical media reading technology uses error correcting techniques to correct errors to ensure data integrity.
• High storage capacity − The storage capacity of optical storage media is higher.
• Strong performance − The performance of Optical storage devices are up to mark as they deliver fast data transfer rates, less access time and high-speed buffering.
• Reliability − The Optical storage devices are reliable.

Disadvantages of Optical Storage

Some of the key disadvantages of Optical Storage are as follows −

• Compatibility − the architectural design of Optical Storage includes different disc formats and standards which makes compatibility issues.
• Access time − Generally, optical storage media has slower access times.
• Scratch and dust sensitivity − optical discs are susceptible to scratches and dust.
• Disk capacity − Disk storage capacity can be improved.
• Plastic disks − The plastic material used to frame an optical disk is not eco-friendly.