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Simplified Schematics of the PWM Write Modulation System. This circuitry is intended to control the pulse duration and power of a laser driver that is used in Pulse Width Modulation (PWM) optical recording.
English (United States)
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This is the abbreviated version, containing approximately
52% of the total text.
Pulse Width Modulation Modulator for Optical Recording
Schematics of the PWM Write Modulation System
circuitry is intended to control the pulse duration and
power of a laser driver that is used in Pulse Width Modulation (PWM)
of portions of the data marks on the media uses a
short pulse such that the media does not move during the exposure
time, for example 10 ns when the media velocity of 18 m/sec.. In
this case, the pulse center timing accuracy can be about 180
picoseconds or about 1% of the channel clock period T. See (*) for
a description of the write process.
laser driver interface is given in Table I.
E, S0, and S1 signals are differential ECL signals for extremely fast
and consistent switching. The E control
signals govern the
application and removal of power to the laser driver. The S0 and S1
signals tell the laser what power to apply.
The S0 and S1 signals
must be stable during the time that the E control signal is applied.
consists of marks and spaces that are recorded on
optical media. The marks and spaces
should have a length that is
some integral number of channel clock periods.
It is assumed that
run length limited codes are used so that there is a minimum and
maximum run length for the marks and spaces.
shows a truth table for a typical modulator that
relates data code run length to laser power pulses. The basic
function comprises a run length detectio...