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Laser mode hopping detection for heat-assisted magnetic recording device

  • US 9,984,719 B2
  • Filed: 12/02/2015
  • Issued: 05/29/2018
  • Est. Priority Date: 12/02/2015
  • Status: Active Grant
First Claim
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1. A method for detecting mode hopping in a laser diode of a storage device, the method comprising steps of:

  • receiving a time-variant signal from a photodetector optically connected to the laser diode while the laser diode is engaged for writing data to a recording media of the storage device, the time-variant signal indicating a light energy output of the laser diode;

    differentiating the signal over time to produce a differentiated signal representing a rate of change in the light energy output of the laser diode;

    determining whether the differentiated signal exceeds a threshold value indicating a rapid change in an oscillation wavelength of the laser diode; and

    upon determining that the differentiated signal exceeds the threshold value, asserting a fault signal to a controller of the storage device indicating a potential write-fault due to a mode hopping event in the laser diode.

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