A study on 3-level/2-level weighted PRML to (1,7) code at the optical diskrecorder

The bit error rate of a (1,7) code for a digital optical disk recorder when the code is regenerated by PRML combining partial response equalization an d 3-level/2-level weighted 4-state Viterbi decoding is derived and compared by simulation with the ideal regenerated waveform (Gaussian waveform). It is found that the bit error is best when the weight w is 0.625 for 10(6) sy mbols of data. For a shortest bit length of 0.28 mu m, the bit error rate ( BER) is 10(-4) at an SN ratio of 17.5 dB and zero error is obtained at 20 d B. Also, at the shortest bit length of 0.26 mu m, the BER is 10(-4) at an S N ratio of 19.5 dB and zero error is obtained at 22 dB. These results are 3 dB better than the case of 3-level 4-state Viterbi decoding (w = 1) and 7 dB better than 2-level 4-state Viterbi decoding (w = 0). Hence, practical r ealization of the shortest bit of 0.26 Irm is found promising. (C) 1999 Scr ipta Technica, Electron Comm Jpn Pt 2, 83(1): 7-16, 2000.