Optical storage

Question 1

What is an optical disk?

Answer 1

A data storage medium using a reflective surface. Lasers shines through this surface to read the data.

Question 2

What are the different lasers used in optical disks?

Answer 2

CDs - Infrared, DVDs - Red Laser Blueray - blue or violet laser.

Question 3

How is data stored on an optical disk?

Answer 3

If a laser is shone onto the surface of the disk one of two things can happen:

1. • The light could hit a pit/bump in which case it is scattered. this is how a 0 is created.
2. The light could hit land/flat area. laser reflected straight back. This is how a 1 is created.

Question 4

What is the difference between CAV and CLV

Answer 4

CAV or constant angular velocity is when a disk always spins at the same speed whereas CLV or constant linear velocity the disk spins at different speeds depending upon where the laser is reading the disk.

Question 5

How is CAV and CLV measured?

Answer 5

CAV is measured in revolutions per minute and CLV distance per second.

Question 6

How are blocks of data different in CAV and CLV?

Answer 6

in CAV a sector of data takes up a larger len gth of track at the outside of the disk than on the inside of the disk, whereas in CLR a block of data is the same length regardless of location.