Shedding light on the future of SP for optical recording

Optical recording has lagged behind magnetic recording in two key areas: writable/erasable/rewritable media and density gains from advanced signal processing. While there are some writable optical-disk products available, their writing capability pales in comparison to magnetic recording. A great deal of research and development in writable/erasable/rewritable optical media continues and we address this in the article. Of particular interest is the use of near-field optical approaches to dramatically increase the storage density in both magnetic and optical recording. To a great extent, this article is about the future of signal processing for optical recording, since advanced signal processing has not been applied to any great extent in optical recording. The intention is twofold: (1) to provide a summary of current and existing optical recording technologies, and (2) to encourage and motivate work in advanced signal processing for these and other optical systems. We begin by summarizing the optical recording and readback processes and then describe writable optical channels and the gains associated with using partial-response coding techniques. We then describe nonbinary recording and the potential gains due to signal processing. The digital versatile disc (DVD), multilayer recording, and holographic recording are also discussed.