<title>Optical Disc Recording At 50 Megabits/Second</title>

Abstract

An optical disc system is being developed to address wideband archival digital data storage applications. This system, which has the capability for "instant" playback (i.e., within a few bit periods), is configured about an RCA-proprietary "trilayer" optical disc structure. The optical disc has the potential for achieving high packing density (1011 bits/disc) and high data transfer rates. This paper discusses the RCA approach and experimental results of the implementation of an error detection and correction (EDAC) scheme and of a 50 Mb/s delay modulation encoding channel. The EDAC has been simulated using a computer program with raw data obtained from a readout of an optical disc at 40 Mb/s. The codes employed are described. The EDAC chosen gives about 100-to-1 improvement in error rates for 10 percent overhead. The 50 Mb/s delay modulation (DM) channel implementation will be described. Waveforms for the encoding and decoding signals are shown, along with a description of the logic circuitry used. Approaches for interfacing the encode/decode circuitry with external data equipment are also considered. The discussion of the DM channel includes a description of the synchronization and data identification signals and the manner in which they are serialized and inserted into the data stream.