  Modal noise in optical fibers imposes limits on the signal to noise and
velocity precision achievable with the next generation of astronomical
spectrographs. This is an increasingly pressing problem for precision radial
velocity (RV) spectrographs in the near-infrared (NIR) and optical that require
both high stability of the observed line profiles and high signal to noise.
Many of these spectrographs plan to use highly coherent emission line
calibration sources like laser frequency combs and Fabry-Perot etalons to
achieve precision sufficient to detect terrestrial mass planets. These high
precision calibration sources often use single mode fibers or highly coherent
sources. Coupling light from single mode fibers to multi-mode fibers leads to
only a very low number of modes being excited, thereby exacerbating the modal
noise measured by the spectrograph. We present a commercial off-the-shelf
(COTS) solution that significantly mitigates modal noise at all optical and NIR
wavelengths, and which can be applied to spectrograph calibration systems. Our
solution uses an integrating sphere in conjunction with a diffuser that is
moved rapidly using electrostrictive polymers, and is generally superior to
most tested forms of mechanical fiber agitation. We demonstrate a high level of
modal noise reduction with a narrow bandwidth 1550 nm laser. Our relatively
inexpensive solution immediately enables spectrographs to take advantage of the
innate precision of bright state-of-the art calibration sources by removing a
major source of systematic noise.
