Pioneer has developed a 16-layer read-only optical disc which it claims can store 400GB of data.

The per-layer capacity is 25GB, the same as that of a Blu-ray Disc, and the multilayer technology will also be applicable to multilayer recordable discs.

Multi-layered discs have been difficult to develop because 'crosstalk' from adjacent layers and transmission loss mean that getting a stable signal from the disc is often nearly impossible.

Pioneer achieved stability in the playback of recorded signals by employing a wide-range spherical aberration compensator and light-receiving element that can read out weak signals at a high signal-to-noise ratio in the optical pick-up mechanism.

The huge capacity of these discs means that the new technology will be best suited for applications such large volume data archiving, rather than consumer use.

Pioneer will present the details of this research at the International Symposium on Optical Memory and Optical Data Storage 2008 in Hawaii on 13 July.