Hitachi-Maxell Develops 8 Layer 200GB Blu-ray Disc

[Ian]

Hitachi-Maxell is really moving on this. It wasn't that long ago that they demoed their 4 layer 100GB Blu-ray Disc.

http://www.hitachi.co.jp/New/cnews/mont ... /0518.html

I found this part to be the most interesting:

In the multilayer optical disk, in order most to read and write even in record layer of the inner part through the plural record layers to be piled up, layer forward becomes the interference, only the little signal light intensity it is possible to detect. In addition, it was necessary to make the reflectance ratio of layer forward low in order to ease this, you make either the signal light intensity of layer forward small did not obtain. When the signal light intensity decreases, the signal is buried to the electric noise which occurs in the photodetector and the circuit, the possibility error occurring in signal reading becomes high. It is possible to expand the signal which you grasp electrically, but in this case, there was a problem also noise is expanded in the same way.

At Hitachi, in order to solve such problem, the detection signal is expanded developed the technology which applies “homodyne detection method” to the optical disk anew then making use of the interference of light. When homodyne detection method, you divide light from the laser illuminant into 2 systems beforehand due to the half mirror, and the like modulate on the other hand with the signal and (below, signal light), playing back, it is the technology which expands the signal the light which one side has not been modulated anymore (below, reference beam) with by interfering. This time, in order to apply this homodyne detection method to the optical disk, optical system of the current optical disk and the optical system technology whose affinity is high were developed. Merit of this technology is as follows.

I hope we see a press release in English soon. This translation sucks.

[dolphinius_rex]

Wow... looks like 200GB Blu-Ray discs really might be in the forseeable future. We'll never see movies on them though

[Ian]

The catch is that you would need a whole new player or drive to read/write these. At least with their 100GB discs, they were able to modify an existing drive to do it.

[Wesociety]

Plus the discs themselves will be REALLY expensive.

[TheWizard]

How practical is this? While it would be great to hold 200GB of data on an optical disc, how well will the disc safeguard our data? My only worry is that the more layers they add to a disc, the more vulnerable it becomes.

[Ian]

Tech-On has some good info on this.

http://techon.nikkeibp.co.jp/english/NE ... 21/132854/

Homodyne detection, widely used in optical communications, is utilized to amplify the reproduction signal. In the homodyne detection, the light beam output from the laser light source is split into two light paths by means of a half mirror or other devices. One of the split light beams is used as the signal light after being modulated and the other is used as the reference light without modulation. Then, the signal and reference lights are interfered with each other on the detector to obtain an electric signal. With the use of this method, even if the intensity of the signal light is low, the amplitude of the coherent light obtained by multiplexing the two lights becomes greater than that of the original signal light, when the intensity of the reference light is high enough. Compared to the case where only the signal light is used, the reproduction signal is less likely to be blocked by electric noises generated by the photodetector and electric circuits since the intensity of light that can be input to the detector is higher. In the experiment, Hitachi succeeded in boosting the S/N ratio of the electric signal output from the photodetector by ten times.