Operating Instructions; Operating Principle - THORLABS PDB47 C Series Operation Manual

Balanced amplified photodetectors

Table of Contents

3 Operating Instructions

Turn the power switch of the power supply to I. The green LED next to the DC input con-

nector indicates correct power supply.

Connect the optical source(s) to the optical input(s). Please note that the PDB47xC is de-

signed for FC/APC connectors!

MONITOR outputs can be used for convenient alignment of a coarse input power balance.

The maximum output voltage swing of the MONITOR outputs is 10V for high impedance

loads. Saturation of the MONITOR outputs 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

For balanced operation illuminate both photodetectors simultaneously and use the

MONITOR outputs to fine-tune the optical power balance by observing voltage on a digital

voltmeter or other low-frequency measurement device.

After finishing measurements, turn power off.

Attention

The damage threshold of the photo diodes is 10 mW (PDB470C) resp. 5 mW (PDB471C)! Ex-

ceeding this value will permanently destroy the detector!

Thorlabs PDB47xC Balanced Amplified Photodetectors consist of two well-matched, pigtailed

photodiodes and an ultra-low noise, ultra-low distortion high-speed transimpedance amplifier

that generates an output voltage (RF OUTPUT) proportional to the difference between the

photo currents of the two photodiodes, i.e. the difference between the two optical input signals.

Additionally, the unit has two monitor outputs (MONITOR+ and MONITOR-) to observe the op-

tical input power level on each photodiode separately. Due to their increased cut-off frequency,

these outputs can also be used to measure low frequency modulated signals on each detector

separately. This allows a signal normalization up to 3 MHz.

The PDB47xC is powered by an external linear power supply (±12 V, 250 mA - included) via a

PICO M8 power connector.

) to avoid saturation.

3 Operating Instructions

Table of Contents

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