Abstract: The disclosure features optical scramblers that can be used with spectrographs and other optical measurement systems, including Doppler-based radial velocity measurement systems and other precision spectroscopy. In one aspect, an optical scrambler includes a first fiber configured to receive measured light from an optical collection system, a second fiber configured to deliver the measured light to a detection system, and an optical coupling element positioned between a light output surface of the first fiber and a light input surface of the second fiber and configured to deliver the measured light from the first fiber to the second fiber. The coupling element defines an output focal position for the measured light that is delivered to the second fiber and the output focal position is located within 50 microns of an output surface of the coupling element.