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Optical Storage Mediums

Optical Storage Mediums

James Ng

The most common way of storing data in a computer is magnetic. We have hard
drives and floppy disks (soon making way to the CD-ROM), both of which can store
some amount of data. In a disk drive, a read/write head (usually a coil of
wire) passes over a spinning disk, generating an electrical current, which
defines a bit as either a 1 or a 0. There are limitations to this though, and
that is that we can only make the head so small, and the tracks and sectors so
close, before the drive starts to suffer from interference from nearby tracks
and sectors. What other option do we have to store massive amount of data? We
can use light. Light has its advantages. It is of a short wavelength, so we
can place tracks very close together, and the size of the track we use is
dependent only on one thing - the color of the light we use. An optical medium
typically involves some sort of laser, for laser light does not diverge, so we
can pinpoint it to a specific place on the disk. By moving the laser a little
bit, we can change tracks on a disk, and this movement is very small, usually
less than a hairÕs width. This allows one to store an immense amount of data on
one disk. The light does not touch the disk surface, thereby not creating
friction, which leads to wear, so the life of an average optical disk is far
longer than that of a magnetic medium. Also, it is impossible to ÒcrashÓ an
optical disk (in the same sense as crashing a hard drive), since there is a
protective layer covering the data areas, and that the ÒheadÓ of the drive can
be quite far away from the disk surface (a few millimeters compared to
micrometers for a hard drive). If this medium is so superior, then why is it
not standard equipment? It is. Most of the new computers have a CD-ROM drive
that comes with it. Also, it is only recently that prices have come low enough
to actually make them affordable. However, as the acronym states, one cannot
write to a CD-ROM...