Introduction
Optical storage is a type of tertiary storage, which comes after a computer’s RAM and Hard Disk. CDs and DVDs are two types of Optical storage, which are low cost, removable, optical storage media. Hard disks are fixed storage within the computer. This is the usual concept whereas there are people who use optical storage similar to hard disks by fixing them inside the computer and thereby making them secondary memory. Optical storage is different from magnetic storage like magnetic tapes, hard disks and floppy disks, and flash memory that makes use of electrical charges. Optical storage media come in various forms depending upon the material, storage size and technology however it is much cheaper than other storage devices. Though hard disk can store large amount of data, it is not considered conveniently movable due to its size and since it is wired to components inside the computer. Optical media is very convenient and has higher recording compactness than other storage media yet they cannot replace a hard disk due to capacity constraint. CDs, DVDs, Laserdiscs, HD-DVDs, Blu-Ray discs etc are some of the popular existing and upcoming optical storage media. According to their usability / reusability the currently used optical media can be categorized as – DVD-ROM, DVD-Video, CD-ROM and CD which are read only (ROM means Read Only Memory); the write-once DVD-R and CD-R (R means Recordable), which use Write Once Read Many (WORM) technology; and DVD-RAM (RAM means Random Access Memory), CD-RW and DVD-RW which are re-writable(RW means Rewritable). CDs are the most widely used optical storage media. A laser ray touching the surface of the CD accesses the data in it. Phase-change disk, which is a sub-type of optical disks, uses a substance that can solidify into either a crystal or some formless shape. Rewritable media such as DVD-RWs and CD-RWs are usually made of Phase-change disks. Magneto-optic disks are composed of magnetic recordable substance but utilize optical technology like laser to write the data (Optical Storage: The Basics).
Optoelectronics
All machines and tools dependent on light come under Optoelectronics. Thus optical storage devices and fiber optics are covered under Optoelectronics (What is optoelectronics). Technically Optoelectronics is the blend of microelectronics and photonics. When they combine, they have the power to create, transfer and control data at exceptional rates. Optoelectronics has become a vital part of Information Technology, Communication and Entertainment businesses. Optical fibre is becoming more popular due to its low cost, weight, data loss and scattering and with the invent of optical fiber amplifier, it is being widely used in local networks and as compressed packaging substitute for electronic equipments. Optoelectronics packaging characterize a key-enabling technology for a broad range of electronic merchandise such as CD players, faxes, DVD players, LCD displays, LAN routers, Digital cameras, laptops, high performance computers, scanners and CD ROMs. A very common use for Optical fiber is for routing a DVD player’s digital audio output to an amplifier’s digital video input. Optoelectronic system consists of an electrical conductor, light emitting sources such as Light Emitting Diode (LED) or Laser Diode (LD), light transmission medium which includes course-plotting and coupling components and channels such as waveguide, free space or optical fiber, light detectors such as photodiode, photo transistors or photo conductors, and amplifiers such as lenses and diffractive components and electrical receiver (Tummala, 2001).
Fiber Optics
Fiber Optic cables transfer data through small wires at the speed of light. Radically different from copper cables, fiber optics present high data broadcast rates over extended distances due to high bandwidths and low attenuation. Light transmits via fibre cables in concurrence with the theory of total internal reflection. There are 3 types of fibre optics which are commonly used – single-mode, multi-mode and graded-index the use of which will depend upon the requirement. Fibre optic amplifiers have contributed to its extensive use in the field of long distance data transfer and voice communication. Fibre optics is also used in military, medical, scanning, sensing and imaging applications and fibre optic illumination (Azzawi, 2006).
Conclusion
Fibre optics and Optical storage devices have changed the phase of data transfer and storage, communication and medical treatment extensively. The hard disk data can be conveniently carried in a single or set of DVDs which may or may not be modified. It has proven to be a far more convenient and cost effective method of data storage and backup media. With fibre optics being widely used in local and wide area networks, data and voice communication has become less expensive and more reliable. The optical cables weigh much less than the earlier copper cables and the attenuation rate is also far lesser. With the invent and development of laser in 1960s, Optoelectronics have developed to such an extent that it has become an integral part of IT, communication, entertainment, military, security and more importantly medical usages. Scanning and Laser correction are the most important aspects of present medical treatment which owes a lot to the development of Optoelectronics.
References
Azzawi. A.A. 2006. Fiber Optics: Principles and Practices. Boca Raton: CRC Press.
Optical Storage: The Basics. (online). Web.
Tummala, R.R. 2001. Fundamentals of Microsystems Packaging. New York: McGraw-Hill Professional
What is optoelectronics. (online). Web.