The balanced photodetector consists of two photodiodes and a differential amplifier. This configuration cancels out the common mode noise of the two. The method of balanced photodetection (or differential photodetection) has been developed for detecting small differences in optical power between two optical input signals while largely suppressing any common fluctuations in the inputs. Depending on the model, either a silicon or InGaAs detector is employed to enable detection in the UV to MIR. These devices are widely used in applications ranging from optical communication to quantum optics and precision measurement.
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