Lightwave Communications LDX-3232 manual IPD Setpoint

CA LI BRATION AND TR OUBLESHOOTING

Remote Calibration of the LDX-3232 Current Source

C H A P T E R 6

Configure the current source in the following manner for the laser current source calibration:

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
IPD SETPOINT	80% of FS	LAS:LDI

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 (IPD) inputs equals the targeted setpoint.

d.After a few seconds, the Current Source will be ready for the actual IPD 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 IPD 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.

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