Laser mode hopping detection for heat-assisted magnetic recording device
AssigneeSeagate Technology LLC
InventorsRobert Matousek, Todd Lammers, Jon David Trantham
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Abstract
Methods and apparatuses for detecting mode hopping in a laser diode or other optical energy source in heat-assisted magnetic recording. An output power of the laser diode or other optical energy source is measured and the output power is differentiated over time to determine a rate of change. If it is determined that the rate of change exceeds a threshold value, a fault signal is asserted indicating a potential mode hopping event.
Claims20
A method for detecting mode hopping in an optical energy source, the method comprising steps of:
- receiving a time-variant signal from a photodetector optically connected to the optical energy source indicating an output power of the optical energy source;
- differentiating the signal over time to determine a rate of change in the output power of the optical energy source;
- determining whether the rate of change exceeds a threshold value;
- and
- upon determining that the rate of change exceeds the threshold value, asserting a fault signal indicating a potential mode hopping event in the optical energy source.
A storage device configured to:
- measure an output power of an optical energy source in an optical heating element of a read/write head configured for heat-assisted magnetic recording (“HAMR”) during a write operation of data to a recording media of the storage device;
- determine a rate of change of the output power over time;
- and
- if the rate of change of the output power exceeds a threshold value, assert a fault signal to a controller of the storage device indicating a potential write fault.
A preamplifier for a hard disk drive (“HDD”) implementing heat-assisted magnetic recording (“HAMR”), the preamplifier comprising:
- a differentiator circuit configured to receive a signal from a photodetector and produce a differentiated signal representing a rate of change in output power of a laser diode at any given time, the photodetector optically coupled to the laser diode in a read/write head in the HDD;
- and
- a threshold detector configured to determine if the differentiated signal exceeds a threshold voltage level, and upon determining that the differentiated signal exceeds the threshold voltage level, assert a fault signal to a controller of the HDD.
Dependencies are inferred from the claim text.