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Pulse Width Modulation Modulator for Optical Recording

IP.com Disclosure Number: IPCOM000117934D
Original Publication Date: 1996-Jul-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 105K

Publishing Venue

IBM

Related People

Belser, K: AUTHOR [+3]

Abstract

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.

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Pulse Width Modulation Modulator for Optical Recording

      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.

      The writing 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.

      The proposed laser driver interface is given in Table I.  The
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.

      PWM data 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.

      Table II 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...