Cb. Peng et M. Mansuripur, Evaluation of partial-response maximum-likelihood detection for phase-change optical data storage, APPL OPTICS, 38(20), 1999, pp. 4394-4405
We describe the application of partial-response (PR) maximum-likelihood (ML
) detection in rewritable phase-change optical data storage. The input to t
his detector, which is simulated in software, is the actual signal (without
any equalization), reproduced from reading of the recorded sequence on an
optical disk. The detection algorithm involves the extraction of the impuls
e response from the readout signal, PR equalization, the adjustment of gain
and recovery of clock, ML sequence estimation with the Viterbi algorithm,
and analysis of PRML performance. With a laser wavelength of 0.69 mu m and
an objective lens with a numerical aperture of 0.6, three Linear densities
are examined: 0.35 and 0.31 mu m/bit without modulation code and 0.2 mu m/b
it with the (1, 7) modulation code. The equalized signal exhibits good eye
patterns, especially at the densities of 0.35 and 0.31 mu m/bit. Analyses o
f noise and bit-error rate indicate that jitter, rather than noise, is the
main obstacle to realizing ultrahigh density in phase-change media with PRM
L detection. We also briefly discuss the problem of the inherent nonlinear
effect in phase-change readout. (C) 1999 Optical Society of America. OCIS c
odes: 210.0210, 210.4590, 210.4770.