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Recording of information: During recording, the input Signal is fed to a laser

diode. The laser beam from the laser diode is modulated by the input signal. It
switches the laser beam on and off. if the beam is on, it strikes the three recording
layers. The beam is absorbed by the bismuth-tellurium layer. Heat is generated
within the layer. This heat diffuses the atoms in the three recording layers. It
forms four-element alloy layer. Now, the layer becomes recorded layers.

Reading Information from disk: During disk read, a weaker, laser beam is
focused on to the disk. It is reflected back. The beam splitter mirror and lens
arrangement sends the reflected beam to the photo detector. The photo sensor
detects the beam and converts it into an electrical signal

WORM DRIVE Applications

 On-line catalogues
 Large-volume distribution
 Transaction logging Multimedia archival.

Rewritable Optical Disk Technologies

This technology allows erasing old data and rewriting new data over old data.
There are two types of rewritable technology: (i) Magneto-optical ii) Phase
change.