Symmetrical InGaAs photodetectors, also referred to as balanced detectors, are used in fiber-optic applications in optical coherence tomography and fiber sensor technology. Mach Zehnder interferometers are also available with integrated symmetrical detectors. To block the CW component (the unmodulated part) of the optical input signal, an AC-coupled version of each detector is offered. Note that the PDB480C-AC, PDB481C-AC, and PDB482C-AC are only available AC coupled. They each have two switchable gains and feature outstanding Common Mode Rejection Ratio (CMRR) of up to 50 dB. Fiber optic coupling sits right at the heart of modern spectroscopic instruments, letting us move light efficiently between a source, a sample, and a detector.
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