Pioneer has developed an optical disc that can hold up to 400G bytes of data easily surpassing previously announced prototypes.

The new disc manages to pack 16 layers, each with a 25G-byte capacity, into a conventional 12-centimeter diameter optical disc. The new discs are similar to Blu-ray Disc technology and slight changes to the hardware on a Blu-ray drive would allow the new Pioneer discs to be used on one.

Pioneer doesn't have any plans to commercially produce the disc but is looking to work with disc manufacturers who would make it themselves. The technology is about ready to enter commercialization, said Michiko Kadoi, a spokeswoman for Pioneer in Tokyo.

A one-sided Blu-rayDisc has 25G bytes of capacity, far less than the Pioneer disc.

Currently dual-layer 50G byte discs are the highest capacity discs available commercially. Various companies have worked on higher capacity discs and TDK previously announced development of a 6-layer disc with 150G byte capacity but that has yet to reach the market.

Getting a clear signal from each recording layer has been a stumbling block for higher capacity discs with more layers, but Pioneer says it has managed to solve this problem by employing technology it developed for DVDs. The new disc has a structure that reduces interference from adjacent layers and so accurate playback is possible from all 16 layers, the company said.

The initial prototype is a read-only disc but the same technology is also applicable to recordable discs.

A current 50G byte Blu-ray Disc can store about 6 hours of digital high-definition TV so the higher capacity discs, if commercialized, would be able to expand this to 48 hours.

Pioneer plans to detail the technology at the International Symposium on Optical Memory and Optical Data Storage 2008 that will be held in Hawaii from July 13.