Sources of noise in phase-change disk data storage

In optical disk data storage, it is essential to control the sources of noise in order to achieve high signal to noise ratio (SNR) and eventually a low byte error rate. There are several major types of noise in optical recording: thermal, shot, laser, media and writing noise. Here, we separate various noises for phase-change (PC) disks and analyze the media noise in some detail. It is shown that the media noise, which corresponds to about 1% fluctuations of the disk reflection coefficient, is the limiting factor for high SNR if one uses the sum detection scheme in the data channel.