Optimization of Write Strategy in a Partial-Response-Maximum-Likelihood System for High-Density Recording

It is difficult to optimize the write strategy by conventional methods in high-density recording systems with very severe intersymbol interference. We have proposed a new method using the index accounting for the linearity of the channel, which is very important in the partial-response-maximum-likelihood detection scheme. It has been confirmed that the minimum bit error rate can be obtained when the linearity of the channel becomes maximum. We have shown the feasibility of a recording capacity of over 20 GB with 120-mm-diameter phase-change media using the blue-violet laser diode with an objective lens whose numerical aperture is 0.65.