Optical Drives 3.3

Optical Disc

A round flat medium used to store data; read using a laser; slower than HDDs or SSDs.

CD (Compact Disc)

Originally developed for digital music; later used for data storage. 74–80 min of audio, 120mm diameter, 1.2mm thick.

CD-RW Writing Technology

Uses photo reactive crystalline coating and a high-power laser to change disc surface. Called "phase shifting."

DVD (Digital Versatile Disc)

Stores video, audio, and data. Single-sided disc holds 4.7 GB. Most drives support read/write.

DVD-ROM

Read-only format of DVD.

DVD-R

Recordable once; supported by older players.

DVD-RW

Rewritable DVD format using crystal encoding.

DVD-RW DL (Dual-Layer)

Two dye layers, 4.7 GB each, total 8.5 GB. Uses semi-transparent outer layer. More expensive.

DVD Dual-Layer Tech

Uses Opposite Track Path (OTP). Older drives may not support DL.

DVD Speeds

Measured in multiples of 1.35 MBps (1x = 1.35 MBps) or 11 Mbps.

Blu-ray Disc (BD)

Newer format for HD video and data. Uses blue laser with shorter wavelength for tighter data packing.

Blu-ray Capacities

Single layer = 25 GB; Double layer = 50 GB; Experimental 20-layer = 500 GB.

Blu-ray Speed

1x = 4.5 MBps.

Blu-ray Compatibility

Most drives have second laser to read CDs and DVDs. No CD/DVD support without it.

Blu-ray Adoption

Replaced DVD as HD standard. HD DVD discontinued by movie studios.

Working with Optical Discs

Disc may take time to spin up. Wait if inaccessible. Drive letters can change with hardware installs.

Access Time

Includes seek time, latency, and spin-up/down time; key performance measure for optical drives.

Manual Eject

If drive won't open, insert straightened paper clip into small hole below the tray.

Protecting Discs – Foil Discs

Some discs use foil on top layer—can be damaged by scratches or markers.

Protecting Discs – Scratches

Store discs in case. Wipe from center to edge to reduce scratch damage.

Protecting Discs – Heat/Aging

Keep discs away from sunlight and heat to avoid damage.