3.6 Calibrating the optical power display
LDC2xx / page 21
3.6 Calibrating the optical power display
Additional to the photodiode current "I
PD
" also the optical power of the laser diode
can be displayed. The actual optical power is shown only after calibration of the
power display. For calibration the potentiometer "CAL PD" (L13) is used.
Select constant current mode CONST I.
With the knob (L10) either set a laser current "I
LD
" or a monitor current "I
PD
" where
the optical output power of the laser diode is known, e.g. from the data sheet of the
laser diode. The better way is to measure the laser power with an external optical
power meter.
Select the display "P
LD
" (L5) with the keys (L18) or (L19).
Calibrate the display "P
LD
" with potentiometer "CAL PD" (L13) to the value of the
actual optical power.
3.7 Analog modulation of the laser diode
To generate a time dependent injection current "I
LD
" or photodiode current "I
PD
" these
settings can be modulated via an independent ground-symmetric modulation input
"MOD IN" (R1). Maximum allowed input vo ltage is –10 V … +10 V, input resistance
>10 k
Ω
.
"I
LD
" and "I
PD
" are calculated as:
I
LD
= I
LD SET
+ I
MAX
* U
MOD
/ 10 V
or
I
PD
= I
PD SET
+ 0.2 mA * U
MOD
with:
I
LD SET
or I
PD SET
:
value set with (L10)
U
MOD
:
voltage at "MOD IN" (R1)
Start operation in constant cu rrent or constant power mode (refer to chapter 3.4 or
3.5) and adjust the desired set value with the knob (L10).
