Rev: 2.4, 16-Jul-2021 © 2021 Thorlabs Page 3
3 Operating Instructions
PDB2xx Series
3 Operating Instructions
· Turn the power switch of the power supply and on the PDB2xx Series to I. The status LED
next to the DC input connector will turn green to indicate that the power supply is operat-
ing correctly.
· Align the optical sources such that they are incident to the input apertures. The MONITOR
output ports can be used to check the detected signal from each free space input beam.
The maximum output voltage swing of the MONITOR outputs is 10V for high impedance
loads (1.5 V into 50 W loads). Saturation of the MONITOR output ports will occur at optical
input power greater than 1 mW.
· The RF output signal must not exceed the maximum RF OUTPUT voltage swing (see
Technical Data ) to avoid saturation. External neutral density filters or attenuators are
recommended to reduce the input light level.
· For balanced operation, illuminate both photodetectors simultaneously and use either the
RF OUTPUT or the MONITOR output ports to fine-tune the optical power balance by ob-
serving voltage on a digital voltmeter or other low-frequency measurement device.
· Do not exceed a maximum power density of 4 W/cm
2
for maximum linearity performance
when measuring focused beams, fiber outputs, or small diameter beams.
· For use in fiber coupled applications, Thorlabs S120-xx series fiber adapters can be easily
mounted to the optical input ports. Thorlabs offers such adapters as well for single-mode
fibers (connector styles FC, SC, ST and LC) and for multi-mode fibers (connector SMA).
· After finishing measurements, turn off the power with the ON/OFF switch (see Operating
Elements ).
Note
To prevent saturation of the balanced amplifier make sure that the power difference between
the optical input ports is less than the saturation power level (see "RF OUT CW Saturation
Power" in the Technical Data section ).
Attention
The damage threshold of the photodiodes is 20 mW! Exceeding this value will permanently
destroy the detector!
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