Interlock Connections; Photodiode Connections; Setting The Pd Bias; Grounding Considerations - ILX Lightwave LDX-3200 Series User Manual

The 9-pin connector marked CURRENT SOURCE on the back panel is used to connect your laser diode to the
LDX-3200. There are connections provided for laser cathode and anode, photodiode cathode and anode, chassis
ground and interlock. The pinout diagram for this connector is shown in Figure 2.2.

Interlock Connections

In order for the laser output to be enabled a short circuit must exist between the Interlock pins (pins 1 and 2) of the
connector. The short can be a direct short across the pins or a switch to prevent laser operation until the switch is
closed. If a short does not exist between these two pins, the INTERLOCK LED will illuminate on the front panel and
the laser output will be disabled.
The interlock terminals on the LASER connector, pins 1 and 2, must be kept isolated from all other connections
including earth ground.

Photodiode Connections

Many laser diode modules contain an internal photodiode that monitors the back-facet emission of the laser. Usually,
this photodiode is internally connected to either the laser anode or cathode.
The photodiode and laser connections to the LDX-3200 Series Precision Current Source are electrically isolated from
ground and each other. So, if a 4 -pin connection is m ade (no common connections) no additional jumpers are
required. Figures 2.1A - 2.1D show the recommended connections and shielding for 3-pin lasers (where the common
connection is internal to the device). A 4-pin laser should be connected with the same shielding as shown in Figure
2.1, but the common connection (between the photodiode and the laser) is optional.

Setting the PD bias

The LDX-3200 Series Precision Current Source provides an adjustable reverse bias of 0 - 5 VDC for the photodiode.
To set the photodiode bias to 5 volts reverse bias, turn the back panel PHOTODIODE BIAS ADJUST fully clockwise.
To set the photodiode bias to 0 volts reverse bias, turn the back panel PHOTODIODE BIAS ADJUST fully counter-
clockwise

Grounding considerations

The LASER outputs of the LDX-3200 Series Precision Current Source are isolated from chassis ground allowing
either output terminal to be grounded at the user's option. Figure 2.1 shows the proper earth-ground shielding for
laser diode/photodiode connections.
HOW TO OPERATE YOUR LDX-3200
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1, 2 Interlock
3 Chassis Ground
4 Cathode Voltage Sense
5 Laser Cathode
6 PD Cathode (+)
7 PD Anode (-)
8 Anode Voltage Sense
9 Laser Anode
Figure 2.2 Back Panel LD Connector
CAUTION
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