Analog Recording on Phase-change Optical Disks

Abstract

Conventional optical recording methods strive to write a pattern of “perfect marks” on the media, then process the resulting read wave form electronically (using filters, equalizers, slicers) to extract the lengths/positions of the recorded marks. We propose to invert this process by concentrating at first on the read process, deciding which wave forms the read channel can and should supply given its particular constraints (e.g., spectral content, bandwidth, noise characteristics, restrictions of the peak amplitude, etc.). Once the desired read waveforms have been identified, we suggest strategies for recording“patterns” (e.g,, amorphous/crystalline regions on phase-change media, magnetic domains on MO media) that can produce the desired waveforms during readout. By employing the heretofore forbidden mark/space patterns at the medium, the proposed analog schemes should be capable of delivering higher recording densities. Also, by allowing the system designer to match the read waveforms to channel characteristics, the proposed schemes should use the available SNR more efficiently.