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-R

Recordable once; supported by older players.

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 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.

CD - Storage Capacity

Standard CD holds 74–80 minutes of audio or 650–737 MB (847 MB total with error correction)

CD - Physical Dimensions

120 mm diameter, 1.2 mm thick

CD-RW

Rewritable; uses photoreactive crystalline coating; write laser causes crystals to form; has 3 speed ratings: write, rewrite, and read

How CDs Work

Pits do not reflect light, lands do; binary data read by laser and interpreted as 0s and 1s via photosensitive device

DVD - Storage Capacity

Single-layer holds 4.7 GB; uses narrower data track vs CD

DVD - Sensitivity to Errors

Narrow tracks require precise laser aim; wobble or imbalance can prevent data reading

DVD-ROM

Read-only format; 4.7 GB capacity; rated in 11 Mbps multiples (e.g., 18x = 198 Mbps)

DVD-RW

Rewritable; 4.7 GB capacity; can be rewritten ~1,000 times; uses same crystal reflection method as CD-RW

DVD-R DL (Dual Layer)

8.5 GB capacity; uses opposite track path (OTP) to reduce seek time; slower write speeds; may have playback delay at layer switch

Blu-ray - Storage

Single-layer = 25 GB, Dual-layer = 50 GB, Triple-layer = 100 GB, Quad-layer = 128 GB

Ultra HD Blu-ray

Supports 4K video (3840x2160), 60 fps, immersive audio; 3 sizes: 50, 66, 100 GB. Supports Digital Bridge (copy to external/portable)

Blu-ray Speed

1X = 4.5 MBps (bytes); 2X = 9 MBps needed for HD video; practical max is ~12X due to wobble at high speeds

CD-ROM

Read-only; stores data using lands and pits; uses reflective light; early drives: 150 kB/s; speeds are multiples of 150 kB/s (e.g., 72x = 10,800 kB/s)