  We demonstrate the generation of a low-noise, octave-spanning mid-infrared
supercontinuum from 1700 to 4800 nm by injecting femtosecond pulses into the
normal dispersion regime of a multimode step-index chalcogenide fiber with 100
$\mu$m core diameter. We conduct a systematic study of the intensity noise
across the supercontinuum spectrum and show that the initial fluctuations of
the pump laser are at most amplified by a factor of three. We also perform a
comparison with the noise characteristics of an octave-spanning supercontinuum
generated in the anomalous dispersion regime of a multimode fluoride fiber with
similar core size and show that the all-normal dispersion supercontinuum in the
multimode chalcogenide fiber has superior noise characteristics. Our results
open up novel perspective for many practical applications such as long-distance
remote sensing where high power and low noise are paramount.
