Optical Drives

Lasers!

"Optical""optical" means something associated with vision or light; in this case, the light used to etch data onto a CD, DVD, or Blu-ray disc data storage means that a laser beam is used to save the data onto a disc.

The laser focuses on a layer beneath the plastic surace and burns tiny "pits" or trenches in the material. The length of the pit decides its value (e.g., "0" or "1").

Optical media"media" is the plural form of "medium," which means "method"--in this case, a method of saving data include CDs"Compact Disc," released in 1982, DVDs"Digital Video Disc" or "Digital Versatile Disc," released in the late 1990's, and Blu-ray"Blu-ray," released in 2006, is named after the color of the laser; blue light has smaller wavelengths, so can write more data in a smaller space. All are the same size and have almost the exact same appearance.

An optical driveRemember what a drive is? No? Then go back to the chapter on Hard Disk Drives! is a machine that reads and/or writes data on the optical discs. Because all optical discs are the same size, drives can be built to use all three types. Usually, however, they are known by the latest type of technology. For example, a DVD drive can use CDs and DVDs, but it is called a "DVD drive."

The different kinds of optical media can be listed this way:

Name Released Capacity Used for: Bigger than:
CD 1982 700 MB Music, data 1 CD = 500 floppy disks
DVD Late 90's 4.7 GB + Video, data 1 DVD = @ 7 CDs
Blu-ray 2006 25 GB + Video, data 1 Blu-ray = @ 5 DVDs

Optical media can also be classified by the ability to read and/or write. For example, when you buy a music CD in the store, you cannot add music to it. Those discs are read-only"ROM," Read-Only Memory. It is possible to buy blank discs which you can record data onto; these are called recordable discs. You can write data on recordable discs, but you cannot erase and then re-write. There is a final category, called re-writable, which allows you to write, erase, and the record again. CDs and DVDs have the same abbreviations for these, but Blu-rays are a little different.

Type Read-only Recordable Re-Writable
CD CD-ROM CD-R CD-RW
DVD DVD-ROM DVD-R DVD-RW
Blu-ray BD-ROM BD-R BD-RE

Caveat Emptor

When you buy blank optical discs for recording, they may be labeled "for audio," "for video," or "for data." However, all blank optical media can be used for any purpose. The "special" discs for "audio" or "video" are just priced higher, but for your purposes, they are the same as the ones for data. The special "audio" and "video" discs cost more as a kind of "piracy tax"; the money is usually just given to the music and movie companies.

For blank CDs, just get the cheapest ones; any discs should be OK. For blank DVDs, however, try to only buy the name-brand ones (the companies you recognize, like Sony, TDK, etc.), as the "off-brand" DVDs often fail.

Media Types

CD:

Compact Discs are primarily associated with audio content. If you are younger than 30, then for all of your life you have known about music CDs. The music CDs you buy in the store typically have only about a dozen tracks or songs. A standard music CD uses the AIFF music format, in which a normal song is about 50 MB in size. MP3s compress"compression" means that the same information (sometimes with quality loss) is stored in a much smaller space the same song to less than 5 MB. If you create an "MP3 CD," you can save more than 120 songs on the CD-R. If you use stronger MP3 compression, you can fit even more onto the disc.

Advantages of the CD: CDs are cheap, costing only 15 yen per disc if you buy a large number at once. CDs are a nearly universal format, meaning that almost any device will read them. CDs are excellent for long-term backup of small files, such as word-processing, spreadsheet, or other such files.

Disadvantages of the CD: CDs are slow and difficult to record. Unlike a Flash USB drive, writing files to a CD requires a multi-step process, and even just a small save can take a few minutes. CD-RWs are more expensive, and take a much longer time to erase and re-write--so much so that few people ever really use CD-RWs. CD-Rs are so cheap, there is not much reason to use a CD-RW.


DVD:

DVDs have the greatest variety. While CDs are pretty much all the same, there are more than a dozen different types of DVD. Some different types are hardly made any more and difficult to find (e.g., DVD-RAM and DVD+R), but there are still a few different types you'll discover.

One important feature introduced in DVDs is layers. In this technology, the laser focuses on different layers inside the disc, one above and one below, to write two different layers of data. This will increase the capacity, but not quite to double the size. Some DVDs also use both sides of the disc for "double-sided" discs with twice the capacity.

Type Capacity Layers Sides Recording Erase / Rewrite
DVD-ROM 4.7 GB 1 1 No No
DVD-R 4.7 GB* 1 1 Yes No
DVD-R DL 8.5 GB 2 1 Yes No
DVD-RW 4.7 GB 1 1 Yes Yes
DVD-RAM 4.7 ~ 9.4 GB 1 per side 2 Yes Yes
DS DL** 17 GB 2 2 No No

* When recording on a DVD-R, usually you are allowed to record only 4.4 GB.
** usually seen only used by companies creating video DVDs

Advantages of the DVD: DVDs are cheap, costing only 20 yen per disc if you buy a large number at once. DVDs have the best price-per-byte saved. DVDs are excellent for long-term backup of large files, such as digital photos, movies, or large numbers of audio files.

Disadvantages of the DVD: Like CDs, DVDs are slow and difficult to record. In fact, most of the disadvantages of the DVD are the same as for CDs.


Blu-ray:

The Blu-ray format is the next-generation DVD, intended mostly for high-definitionHi-def, or HD, means video which has higher resolution. Traditional TV shows 480 lines of resolution; HD shows 720 or 1080 lines. video but can also be used for data storage. Initially, there was a battle between Toshiba's HD-DVD and Sony's Blu-ray, but Blu-ray won in 2008, and is now spreading, albeit slowly.

CDs and DVDs use red lasers to write data. Red is a lower-frequency color, blue is higher frequency. This means that waves of blue light are smaller and closer together, allowing for more data to be written in a smaller space.

It's like using a thinner, sharper pencil to write smaller text. Imagine trying to write a note on an index card. If you use a thick felt pen, you can only write a few words. But if you use a sharp pencil, you can write much more.

Blu-ray also makes use of layers, just like DVDs. While DVDs use only two layers, Blu-ray media can have many more layers. Each layer can have a capacity of 25 GB. Right now, 25 GB and 50 GB discs are common, and 100 GB Blu-ray discs are beginning to appear. Companies making the discs have been able to create Blu-ray media with as many as 16 layers for 400 GB of storage; in a few years, they hope to make a 40-layer disc with a 1 TB capacity.

Blu-ray Capacities
Layers 1 2 4 8 16 40
Capacity 25 GB 50 GB 100 GB 200 GB 400 GB 1000 GB

Advantages of Blu-ray: Blu-ray disks have very high capacity, the highest of any removable storage media.

Disadvantages of the DVD: Like CDs and DVDs, Blu-ray devices are slow and difficult to record. Again, most of the disadvantages of the CD and DVD are the same for Blu-rays.

 

Types of Optical Drives

Here is a list of drives by which media they can play, and what they are named. For the test, remember what these names mean.

CD-ROM
CD-R/RW
Combo DVD
Super
Super-Multi
Blu-ray Combo Blu-ray Burner
CD-ROM
O
O
O
O
O
O
O
CD-R/RW
X
O
O
O
O
O
O
DVD-ROM
X
X
O
O
O
O
O
DVD-R/RW
X
X
X
O
O
O
O
DVD-R/RW DL X
X
X
X
O
O
O
Blu-ray BD-ROM X
X
X
X
X
O
O
Blu-ray BD-R/RE X
X
X
X
X
X
O