System for performing optical spectroscopy including interferometer

A system for performing optical spectroscopy measurements includes a light source for generating an input optical beam and an interferometer. The interferometer includes a beam splitter that splits the input optical beam into first and second light beams; a first light path that directs the first light beam through a sample containing an analyte to a first output port; and a second light path that directs the second light beam to the first output port. At least one of the first and second light paths adjusts a relative phase of a corresponding one of the first and second light beams, so that the first and second light beams are out of phase at the first output port, substantially canceling background light and outputting sample light corresponding to a portion of the first light signal absorbed by the sample in the sample cell. A detection system detects the output sample light.