Lightwave Communications LDX-3232 - Manual (Page 113)

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
Remote Calibration of the LDX-3232 Current Source
04_06 LDX-3232 97
C H A P T E R
6
Configure the current source in the following manner for the laser current source
calibration:
a. With the LASER output off, connect a calibrated ammeter to the PD Anode output of
the Laser Current Source output connector (9 pin on rear panel), and connect the
circuit of Figure 6.1 to the LASER and PD outputs with the correct load resistor for
the Current Source model you are calibrating (See Table 6.2).
b. Enter the LAS:OUT ON command to turn the LASER output on. Verify proper
operation, i.e. the IPD output should be close to the setpoint, and the unit should not
be in current limit (read the limit status via the LAS:COND? query, bit 0).
c. Enter the LAS:CAL:MDI command to place the Current Source in its LASER Current
Calibration mode. The Current Source will increase the laser current output until the
current at the PD monitor (I
PD
) inputs equals the targeted setpoint.
d. After a few seconds, the Current Source will be ready for the actual I
PD
current to be
entered via the LAS:MDI <nrf value> command. The measured value of the
current should not be entered until the Current Source is ready to receive it. The
Current Source will be ready to receive the current value when, after a
LAS:CAL:MDI?
query is sent, the response from the Current Source is "1".
e. Once the actual I
PD
value is entered via the LAS:MDI <nrf value> command, the
Current Source will store the new calibration value. It will then set the output to
approximately one-fourth (1/4) of the original current. (For example, if the first
calibration setpoint was 4000 µA, the second setpoint will be 1000 µA.) Then, it will
be ready to receive the second calibration value.
f. Input the second actual (measured) monitor diode current (as an <nrf value>) as
in Step d.
g. Once the second actual IPD value is entered via the LAS:MDI command, the new
calibration constants will be calculated and stored into non-volatile memory. The
OPC?
query may be used (after the LAS:MDI value is sent) to determine when the
calibration is completed. Or, wait about two seconds before continuing with other
GPIB commands.
Function State GPIB COMMAND
LASER MODE I (constant current low bandwidth) LAS:MODE:ILBW
RANGE Low (lowest per instrument model) LAS:RAN x
LIMIT 90% of FS (full scale of range) LAS:LIM:Ix
I
PD
SETPOINT 80% of FS LAS:LDI