Lightwave Communications LDX-3232 - Manual (Page 107)

C A L I B R A T I O N A N D T R O U B L E S H O O T I N G
Local Calibration of the LDX-3232 Current Source
04_06 LDX-3232 91
C H A P T E R
6
Figure 6.1 I
PD
Calibration Circuit
Local Calibration of the LDX-3232 Current Source
There are three calibration adjustments required for the LASER current source of
the LDX-3232 Current Source. They are calibration of the constant current source
for both bandwidths and ranges, calibration of the laser voltage measurement,
and calibration of the constant light power (I
PD
) feedback circuits.
The LDX-3232 Current Source implements a two-point calibration for the Laser
current source. Two currents (approximately 80% and 20% of FS) are applied to
a test load, and the resulting actual currents are fed back (by the user) to the
Current Source. The Laser Current Source calibration program uses the two sets
of data to calculate new calibration constants. These calibration constants are
used to set the actual current output of the current source.
Current Source Calibration
The following procedure is for calibrating each range of the current source.
Calibration must be performed on both bandwidth modes. A total of four
calibrations will be performed on the current source. Start with the low range, low
bandwidth mode. Configure the Laser Current Source in the following state:
Function State
MODE I (constant current low bandwidth)
RANGE low (lowest per instrument model)
CURRENT LIMIT 90% of FS (full scale of range)
SETPOINT 80% of FS
U 1 TIL117
1
2
3
4
5
6
A
V
R 3 R2
100
9-Pin D-Sub
LD C athode (5)
LD Anode (9)
PD C athode + (6)
PD Anode - (7)
Voltm eter
Am m eter
R1
49
Ipd C urrent
R4
1 M
CA LIB R ATIO N C IR C U IT