Teledyne LeCroy AORM - Advanced Optical Recording Measurements - Manual (Page 35)

AORM Software Package
923133 Rev A ISSUED: June 2013
33
• For the entire signal, only a space can be identified after a pit, and only a pit can be
identified after a space.
• All subsequent features are identified by crossing into the appropriate zone after the end
of the previous feature. For a pit this is Zone 3, and for a space it is Zone 1. The end of
the previous feature is the beginning of the current feature being identified. The
subsequent first time the signal crosses the voltage threshold is recorded as the time of
the feature being identified. At this point, the feature has been fully identified.
nT Pit/Space Categorization
Because optical recording data is encoded using a pulse-width modulation mechanism, it is often
useful to perform signal analysis for selected pulse widths. Exploiting the fact that optical
recording data widths are ideally integral multiples of the data clock period ‘T’, the AORM
Package separates optical recording signal pits and spaces into groups whose widths fall into the
same integral multiple of clock periods. As a result, ORMs can be configured to provide values for
only pits or spaces, or both of these for a selected ‘nT’ value (‘nT’ denotes an integer multiple of
the clock period) or for a range of ‘nT’s.
The ideal clock period (T) is configured on the parameter nT setup.
Categorization of pits and spaces by nT based on width is done using the following equation:
When this condition is met, the pit or space of width w is said to belong to the n th index.
( ) ( )
T n w T n
⋅ + < ≤ ⋅ −
5 . 0 5 . 0