Pioneer developed a Blu-ray disc compatible disc that can hold 400GB of data on 16 layers. The company for now only has a read-only disc available but expects that it will also be able to produce recordable discs. Each of the layers can hold 25 GB of data, the equivalent of one singel Blu-ray disc layer.

Multi layer discs exist for a while. Normal DVD players and burners are usually able to read and write to dual layer discs and also with the introduction of Blu-ray there was a lot of talk about multiple layers straight away.

It has been a challenge for Pioneer to get a clear signal from each of the recording layer of the disc, in such a way that the data was read straight from one layer with no distortion of data from other layers. Pioneer invented a disc structure that can reduce crosstalk from adjacent layers, resulting in a 16-layer optical disc that can playback high-quality signals from every layer. 

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. Since the optical specifications of the objective lens, such as the distance from the lens to the disc, are the same as those for the current Blu-ray discs, it is possible to maintain compatibility between the new 16-layer optical disc and the Blu-ray discs.

As usual with these kind of technologies, no data on availability and pricing has been given.