Browse Prior Art Database

Verifying Optical Recording

IP.com Disclosure Number: IPCOM000040367D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Spires, RK: AUTHOR [+2]

Abstract

To verify recording in magneto-optic materials, it is desirable to have a dual-acting read channel. This read channel reads recorded data during a read-while-write operation with a degraded signal-to-noise ratio (SNR). Such a degraded read operation amplifies any defects in the written data. Subsequent read-only operations with an improved SNR reliably read all of the recorded data. A read channel may have this selectable SNR in two ways. The first way is that a read laser (not shown) would have reduced power during read-while-write and have its power increased during a readback operation. This produces a degraded SNR during read-while-write, so that data errors will occur as write checks. The SNR is increased during readback by increasing the laser's power. This avoids readback errors.

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Verifying Optical Recording

To verify recording in magneto-optic materials, it is desirable to have a dual- acting read channel. This read channel reads recorded data during a read-while- write operation with a degraded signal-to-noise ratio (SNR). Such a degraded read operation amplifies any defects in the written data. Subsequent read-only operations with an improved SNR reliably read all of the recorded data. A read channel may have this selectable SNR in two ways. The first way is that a read laser (not shown) would have reduced power during read-while-write and have its power increased during a readback operation. This produces a degraded SNR during read-while-write, so that data errors will occur as write checks. The SNR is increased during readback by increasing the laser's power. This avoids readback errors. Second and more subtle method of degrading the SNR during a read- while-write is to have two lasers. It is known that there can be two rotation amplitude peaks to the magneto-optic Kerr rotation phenomenon. From the graph it is seen that a read-while-write laser at peak RB produces a more significant Kerr rotation than the lower laser power produces at peak RW. Thus, the readback laser power would increase SNR by a factor of three over the read- while-write laser power level. Therefore, one can detect errors in data before long streams of data were recorded. Thus, the data could be corrected immediately, instead of at the end of the data writing pass....