What is an Optical Drive?


What is an optical drive? Optical drives have largely taken over from the floppy disk drive as a faster and vastly increased storage capacity medium.

The old floppy drive capacity of 1.44MB has been increased to 600MB for the CD (Compact Disc) optical drives and 4.5GB for single layer DVD (Digital Versatile Disc) optical drives and 9GB for dual layer DVD optical drives.

So just what is an optical drive?

Magnetic and Optical Storage

On a PC there are in the main two types of bulk storage (although that has started to be challenged recently by the Solid State Disk drives).

Firstly we have magnetic storage such as that used by your hard disk drive or old floppy drive and secondly optical disc storage.

Both involve rotating disks which are written and read from but the optical drives use an optical light (laser) rather than a magnetised disk and read/write magnetic head.

Although it was once hoped that optical storage would advance to the point where it would challenge magnetic hard disk drive storage it has become evident that optical storage is less capable of being written to and read from as fast as the magnetic hard disc drives.

Backup

The optical drive has lent itself very well as a removable storage medium whereby a backup or distribution of software, data, music, films etc can be carried out with the main PC storage remaining with the hard disk drive, as it is a much faster device and capable of holding significantly more data.

The optical drives and media themselves are very inexpensive.

How does it work?

The optical drive writes and reads to a thin plastic disc which has a very fine spiral track with dips and bumps along it.

The disc has an aluminium backing on the other side and the drive uses a laser and receiving optics to read the surface of the spiral track by bouncing the beam from the laser off of the reflective layer of the disc formed by the metal coating on the far side of the disc behind the spiral track.

When the laser hits a dip the light is reflected back and when it hits a bump no light is reflected back and so a digital 1 0 etc data pattern is formed by the dips and bumps along the spiral track.

The dips and bumps are either created by being stamped or pressed at a factory or by a laser within your PC optical burner drive when you ‘burn’ your own disc for data storage.

The disc is spun with a motor assembly and the laser and associated lens, used to read the reflected light, is tracked along the spiral track using a precision tracking mechanism allowing the laser to read the data as it travels along the spiral.

What's available?

The first PC optical drives were only capable of reading from CDs distributed by software and music companies and the like but soon along came optical drives capable of writing to commercially available blank disc media.

This was quickly followed by DVD technology with increased capacity.

Dual layer discs are available effectively doubling the capacity of a single disc.

This is achieved by adding a second data layer with a semi-reflective backing.

Both of these layers are accessed from the underside of the disc by a change in focusing of the laser optics.

Interface

Internal optical drives will connect to the PC system using an IDE or SATA interface whilst external optical drives will typically use the USB or Firewire interfaces.

Blu-ray drives

The latest development of optical drives incorporates Blu Ray drive technology.

These drives are capable of a phenomenal 50GB of data storage in dual layer format and are also backward compatible with the older CD and DVD media.

Currently the Blu-ray drive is the new kid on the block and blank media prices are still high but that will soon change.

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