Optimization of write strategy in a PRML system for high density recording

Recently, there has been much research on high density recording using an NA = 0.85 objective lens . The use of PRML (partial response-maximum-likelihood) is an efficient way to handle inter-symbol interference (ISI) that degrades the bit-error-rate at a very high recording density. We have shown that the recording capacity of about 32 GB is achieved with the use of PR channel with a constraint length of 5, i.e., PR (12221) and Viterbi detection in the NA = 0.85 system. This paper describes the method for optimizing a write strategy in the PRML system. We have confirmed that the write strategy can be optimized in terms of a linearity of the channel. It has been found that the recording density near the optical cut-off frequency can be achieved by using the optimized write strategy and PRML.