
O P E R A T I O N S
Operating from the Front Panel
02_03
LDC-3926339
15
C H A P T E R
2
Operating in Constant Current Mode
There are two constant current modes: low bandwidth (ILBW) and high bandwidth
(IHBW). The low bandwidth mode uses a low-pass filter on the laser drive current
output to reduce noise, while the high bandwidth mode bypasses this filter. Use
low bandwidth mode for CW operation or if the modulation frequency is below 27
kHz; use high bandwidth mode if the modulation frequency is above 27 kHz.
1
Press
CHAN
to display the channel menu. From this menu, you can see the measured
parameters.
2
Use the INC/DEC keys or the Adjust knob to select the desired channel number
highlighted at the top of the display.
3
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 control 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.
4
Set the control mode.
4a
Press
NEXT
until the Mode field is highlighted.
4b
Select
Ilbw
or
Ihbw
using the INC/DEC keys or the Adjust knob.
Note:
Repeatedly pressing the INC/DEC keys or turning the Adjust Knob cycles through
the Constant Current low bandwidth (
Ilbw
), Constant Optical Power (
P
), Constant Current
high bandwidth (
Ihbw
), and Photodiode Current (
Ipd
) control modes.
Figure 2.6
Constant Current Mode Setup, Laser Page 1
5
Select the voltage limit (Vlim) and current limit (Ilim).
5a
Press
PREV
to select the voltage limit (
Vlim
) parameter.
5b
Using the Adjust Knob or the numeric keypad, set the Vlim value and press
ENTER
.
You must press Enter within three seconds of selecting the value.
Set the voltage limit slightly above the operating voltage of the laser diode to provide
maximum protection. The voltage limit protects your laser by shutting off the source driver
if the laser voltage exceeds the Vlim value.
5c
Press
PREV
to select the current limit (
Ilim
) parameter.
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