Lightwave Communications LDX-3232 - Manual (Page 102)

FU N C T I O N S A N D FE A T U R E S
Using the LDX-3232 Current Sources’s BNC Interlock Connection
86 LDX-3232
C H A P T E R
5
Using the LDX-3232 Current Sources’s BNC Interlock
Connection
The LDX-3232 BNC interlock connection is designed to allow an external
emergency input signal to turn the current output off. The BNC interlock is TTL
compatible and configured to be normally closed (as opposed to the DB-9
interlock connection, that is normally open). The BNC interlock connection, when
left unconnected, is pulled to a logic high with a 100 k
Ω resistor. High values
(+5 V) will keep the interlock closed (current source in the operational state), while
low values (0 V) will open the BNC interlock (forces the output off). Once the
BNC interlock is opened, the output will stay off until the interlock is closed again,
and you re-enable the output.
BNC Interlock Usage Example
When using the LDX-3232 Current Source to drive a temperature controlled laser
diode, the BNC interlock can be used to accept an error signal from the laser
diode temperature controller unit. Linking the LDX-3232 Current Source to a
temperature controller* with the ability to signal when its temperature control has
gone outside of some tolerance window will allow the LDX-3232 to safely shutoff
its output before thermal damage occurs to the laser diode.
*The ILX Lightwave LDT-5900 series of temperature controllers include an output
BNC connector that is compatible with the BNC interlock feature of the LDX-3232.
The output BNC connector of the LDT-5900 has a TTL compatible output signal
that will signal when the temperature control has gone outside of a programmable
temperature window. For more information about the LDT-5900 series of
temperature controllers, please call 1-800-459-9459 (USA or Canada only),
1-406-556-2481 (International), or go to www.ilxlightwave.com.
Modulating the Laser Current Source
The LDX-3232 Current Source allows a modulated signal to be superimposed on
the source output current. For example, assume you are using an LED for your
experiment where you need to operate the LED in constant current at P
OP
=
100 mW, with a modulated signal from 3 to 30 kHz. The experiment requires the
LDX-3232's laser Current Source to be configured for the 2000 mA range, high
bandwidth mode with a limit of 1750 mA. The allowable bandwidth of the
modulated analog signal, defined as the 3 dB roll off point, is dependent on the
output current range and the mode (constant current low/high bandwidth). See the
section, LASER CURRENT SOURCE SPECIFICATIONS, in Chapter 1 for
external analog modulation bandwidth specifications.