Operating A Laser In Constant Power Mode (P); Figure 2.8 Laser - ILX Lightwave LDC-3926339 User Manual

Operating a Laser in Constant Power Mode (P)

The LDC-3926339 module allows you to operate the current source driver in
Constant Optical Power (P) mode. In P mode, the module drives current to the
laser to maintain a set power value (in mW).
The control loop feedback parameter is a monitor photodiode current. The
controller converts the monitor photodiode current to optical power via a user
defined photodiode responsivity, CalPD. If laser power changes due to internal or
environmental conditions, the controller increases or decreases the current to the
laser to maintain the power setpoint.
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Calculate the photodiode responsivity (CalPD) value.
The photodiode responsivity, CalPD, is a transfer function that converts photodiode
current to optical power of the laser diode.
Measure the output power of the laser with a calibrated detector.
Measure the corresponding monitor photodiode current (MPD).
Using the measured values for output power and MPD, calculate the responsivity
(CalPD) by dividing the photodiode current by the optical power. The units required
are mA/mW.
Press CHAN to display the channel menu.
Use the INC/DEC keys or the Adjust knob to select the desired channel number
highlighted at the top of the display.
Press the LAS soft key to enter page 1 of the laser channel setup menu.
From LAS page 1 menu, set the Current setpoint (ISet), the Current limit (Ilim), the
Voltage limit (Vlim), and the mode (Mode). This page also displays measured current
output and laser forward voltage. You can also turn the controller on or off from this page.
Figure 2.8 Laser Page 1
Set the current source mode to Constant Optical Power mode (P).
Press NEXT until the Mode field is highlighted.
Select P using the INC/DEC keys or the Adjust knob.
O P E R A T I O N S
Operating from the Front Panel
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LDC-3926339