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Here is its block diagram:
The APC loop offers the best performance for a stable the optical power, since it is able to react against
eventual deviations.
POWER VERSUS CURRENT CHARACTERISTICS AND MODULATION
Here are the typical characteristic functions obtained when driving the laser using one of these methods:
- setting an internal (=software) set point,
- applying an external signal for analog modulation, or
- applying an external signal for digital modulation
APC MODE, INTERNAL SET POINT
Here is a typical characteristic curve of a LaserBoxx LBX or LCX driven by an internal set point, in APC mode:
The characteristic curve is linear between 0mW and the nominal power, the effect of the APC loop being that
the monitored power is strictly equal to the power set point. Note that the exact value of the nominal power
(200mW in the example above) is specified on the manufacturing test report of each unit.
Reading or setting the optical power in done in milliwatt.
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