Thermal interference in high density magneto-optical recording and a method of compensation

Abstract

In order to achieve high density recording in a magneto-optical disk, much attention has been paid to reduce thermal interference between the recording pulses1,2. This is because thermal interference causes the variation of the recorded domain size and shape2. The domain size and shape fluctuation introduces peak shift and amplitude variation of the optical readout. This effect is significant3 when the separation between the data bits is small in a high density recording medium. For a disk drive using domain-edge recording, the peak shift introduces timing jitter relative to the timing clock pulse. In a sampled servo disk drive, the amplitude variation results in deterioration of the margin of the amplitude threshold detection4. The timing jitter in edge-recording disk drive and erosion of amplitude threshold detection margin in a sampled servo disk drive both result in carrier-to-noise ratio reduction and thus larger bit error rate of the system. In this paper, a sampled servo drive is used to study the readout amplitude variation due to thermal interference in successive recording pulses. A simple compensation technique is demonstrated to achieve uniform optical readouts of the recording data bits in successive recording pulses.