Lightwave Communications LDX-3232 manual Lasldi nrf value command

C H A P T E R 6

CALIBRATION AND TR OU BLESHOOTING

Remote Calibration of the LDX-3232 Current Source

a.Measure and record the resistance of a 1 Ω, 20 W resistor. (A 4-wire [Kelvin] resistance measurement is recommended.) Connect the load resistor across the LASER output terminals (Laser Anode and Laser Cathode) on the 9 pin connector of the rear panel.

b.Connect the calibrated DMM across the load resistor. Configure the multimeter to measure voltage in volts. You will be calculating the actual Laser current in the following manner using Ohm's Law.

I = V/ R

--where V is the accurately measured voltage across the resistor, and R is the accurately measured load resistance in Ohms. I is the actual Laser current in Amps.

c.The current source output must be on in order to enter the LASER I calibration mode. Enter the LAS:OUTPUT ON command to turn the current source output on.

d.Enter the LASER I calibration mode by issuing the LAS:CAL:LDI command. The display will indicate a current in mA.

e.Input the first actual (measured) output current (as an <nrf value>) via the

LAS:LDI <nrf value> command.

If this value is to be measured and entered remotely via a GPIB controlled DMM, for example, the measured value of the current should not be entered until the LDX-3232 Series Current Source is ready to receive it. The Current Source will be ready to receive the new measured value when, after a LAS:CAL:LDI? query is sent, the response from the Current Source is "1".

f.Once the newly measured I value is entered via the LAS:LDI command, the Current Source will apply a new current equal to about 25% of the previous set current.

g.Input the second actual (measured) output current (as an <nrf value>) as in Step e.

h.Once the second actual I value is entered via the LAS:LDI command, the new calibration constants will be calculated and stored into non-volatile memory. In low bandwidth calibration mode, the LDX-3232 Current Source will also perform current limit calibration as indicated by the CURRENT LIMIT LED flashing. The OPC? query may be used (after the LAS:LDI value is sent) to determine when the calibration is completed. Or, wait about two seconds before continuing with other GPIB commands.

i.Turn the current source output off. Change the Mode to IHBW (high bandwidth constant current mode) with the LAS:IHBW command. Repeat the calibration procedure as described above.

IPD Current Calibration

The following procedure is for calibration the LASER IPD constant current source. This procedure calibrates the feedback circuits for constant IPD and constant PPD modes. When these values are reached and are stable, the user enters the actual value of the current, as measured by an external DMM. The LDX-3232 Current Source then automatically calibrates the LASER feedback circuits.

96 LDX-3232