Resources - Archiving & Storage Whitepapers - Blu-ray Disc FAQS

What is Blu-ray?
Blu-ray Disc (BD) is the next-generation optical disc format. While current optical disc technologies rely on a red laser to read and write data, the new format uses a blue-violet laser instead. Despite the different type of lasers used, our Blu-ray products are backwards compatible. The benefit of using a blue-violet laser (405nm) is that it has a shorter wavelength than a red laser (650nm), which makes it possible to focus the laser spot with even greater precision. This allows data to be packed more tightly and stored in less space, so its possible to fit more data on the disc even though its the same size as CD/DVD. This together with the change of numerical aperture to 0.85 us is what enables Blu-ray Discs to hold 25GB/50GB.

What Blu-ray Disc variants are available?
As with CD and DVD, Blu-ray Disc media comes in pre-recorded, recordable and rewritable variants. The pre-recorded disc is called BD-ROM. The recordable disc is called BD-R, and can be used for archival of huge amounts of data or video. The rewritable disc is called BD-RE, and offers the same large capacity in a disc format that allows for repetitive usage.

What is the capacity of a Blu-ray Disc?
All three Blu-ray Disc types come in two versions: single layer and double layer. A double layer disc may hold up to twice the amount of data or video compared to a single layer disc, and uses two independent layers placed on one side of the disc to store its information. A single-layer disc holds up to 25 gigabytes, while a double-layer disc holds up to 50 gigabytes of data, without the need to flip the disc. Blu-ray Disc format is easily extendable (future-proof) as it includes support for multi-layer discs. This allows the storage capacity to be increased to 100-200GB in the future simply by adding more layers to the discs.

What is the expected media life of Blu-ray Discs?
TDKs internal tests show that BD-R SL media are extremely suitable for long-term archival storage purposes. In a typical office environment (normal room conditions), the projected archival lifespan for a TDK BD-R 25GB (single layer) is 190 years .

Can I play a Blu-ray Disc on my DVD player?
Implementation of DVD or CD recording capability is a manufacturers option but Blu-ray Discs can not be played on DVD players. The red (DVD) laser is not capable of reading the very fine pits of a Blu-ray Disc, which requires a blue laser. DVD-Video players also lack the advanced technology to decode the High Definition picture from a Blu-ray Disc.

How fast can you read/write data on a Blu-ray disc? First generation drives are 2x (72Mbps), as
BD-ROM movies require a minimum data transfer rate of 54 Mbps. Blu-ray also has the potential for much higher speeds, as a result of the larger numerical aperture (NA) adopted by Blu-ray Disc. The large NA value effectively means that Blu-ray will require less recording power and lower disc rotation speed than DVD and HD-DVD to achieve the same data transfer rate. While the media itself limited the recording speed in the past, the only limiting factor for Blu-ray is the capacity of the hardware. If we assume a maximum disc rotation speed of 10,000 RPM, then 12x at the outer diameter should be possible (about 400Mbps). This is why the Blu-ray Disc Association (BDA) already has plans to raise the speed to 8x (288Mbps) or more in the future.

Will Blu-ray discs require a cartridge?
No, the development of new low cost hard-coating technologies has made the cartridge obsolete. Blu-ray will instead rely on hard-coating for protection, which when applied will make the discs even more resistant to scratches and fingerprints than todays DVDs, while still preserving the same look and feel. Blu-ray also adopts a new error correction system which is more robust and efficient than the one used for DVDs.