Operation - THORLABS APD440A Operation Manual

APD440x
Mounting External Optics
The APD440x housing allows to mount external optics, filters, apertures or fiber adapters. For
this, it features Thorlabs' SM05 (0.535"-40) threads and SM1 (1.035"-40) threads that are com-
patible with any number of Thorlabs 1" and ½" threaded accessories. This also allows conveni-
ent mounting of lens tubes or cage systems. For accessories, please visit our website or con-
tact Thorlabs .
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The APD440x is delivered with an SM1 coupler (SM1T1) which adapts the external thread to an
internal SM1 thread and holds the SM1RR retaining ring and a reusable protective plasic cover
cap. Please unscrew the coupler if needed.

3.3 Operation

Attention
Prior to connecting the power supply to the mains power, ensure that the correct mains voltage
is selected on the power supply
power supply. The ±12 V, 250 mA power supply is included, no high voltage power supply is re-
quired for operation.
Attention
Exceeding the optical damage threshold input power will permanently destroy the detector!
Please see the Technical Data
Electrical Setup
Mount the detector using the combi-thread mounting holes on either side or on the bottom
·
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of the device.
· Plug the power connector cable into the POWER IN.
· Plug the power supply into an outlet.
· Connect the OUTPUT connector jack (BNC) to your data acquisition device with a
cable. Please note that a 50 W impedance device should be used for best RF performance.
· Switch on the power supply.
· Move the power slider to I to turn on the APD440x. The green LED on the APD440x indicates
the correct power supply.
Gain Adjustment
The Gain can be adjusted to achieve an optimal signal to noise ratio (SNR).
The photo-current generated by signal light is amplified by the gain. Because APDs generate
noise due to the multiplication process, the noise also increases as the gain is increased. This
means that the best SNR for a specific optical input signal exists at a specific gain that can be
adjusted.
How to adjust the gain:
· Turn the GAIN knob to minimum before applying the optical signal to the APD440x. This is
the condition when the APD440x is least sensitive, can tolerate its highest optical input level
and has the lowest noise level.
· Align the light source with the optical input. To avoid electrical saturation, keep the output
voltage below this maximum listed in the
attenuators are recommended to reduce the input light level in critical cases.
· Increase the gain to achieve the optimal signal.
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. Wrong settings for the mains voltage may damage the
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for the maximum input power.
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Technical Data . External neutral density filters or
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coaxial
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