Lightwave Communications LDX-3232 manual E R a T I O N

C H A P T E R 2

O P E R A T I O N

Operating a Laser in Constant Current (I) Mode

To set the current source limit, use the SELECT push button in the PARAMETER section of the front panel to select LIM I. Press and hold the (PARAMETER) SET push button and rotate the adjust knob to vary the limit setpoint value. Set the limit to 1750 mA. Once the (PARAMETER) SET push button is released, the new parameter value is stored in non-volatile memory.

When the LASER current limit is reached, the CURRENT LIMIT error indicator flashes. The current limit setting is independent of the voltage drop of the device connected to the LASER output, and therefore, no dummy load is required for precise adjustment of the current limit. Furthermore, since the current limit circuitry is fully independent of the main current control, the current limit can be adjusted safely, even while the LASER output is active.

An additional feature of the LDX-3232 instrument is an adjustable voltage limit. This allows an extra level of laser protection in the event of an intermittent open circuit. For maximum protection via the fastest open-circuit detection, the voltage limit should be set to a value slightly greater than the intended operating voltage.

To set the LASER voltage limit, use the SELECT push button in the PARAMETER section of the front panel to select COMP V and then press and hold the (PARAMETER) SET push button. While holding the (PARAMETER) SET push button, adjust the voltage limit using the adjust knob.

Now you are ready to enable the current source output for your laser diode.

In the MODE section of the front panel, press the push button labeled OUTPUT. The accompanying LED labeled ON will illuminate, indicating that the laser current source's output is enabled. The instrument will drive the current source to the value set by the corresponding MODE setpoint. When the LASER output is off, an internal short is placed across the LASER output. The OUTPUT switch has a toggling action. Pressing the switch again will disable the current source output and the ON LED will not be illuminated. The default condition for the current source output is off when the instrument is first powered up. With the laser output enabled, the LASER display should be indicating measured laser current. If the output won't function, check the following conditions:

16 LDX-3232