A powerful class of techniques utilizing frequency combs is that of multiheterodyne techniques. These techniques use each individual, evenly space, spectral line of a comb as a local oscillator to measure a source's spectrum. By mixing an unknown source with that of a comb one can convert an optical signal into an electrical signal where standard radio-frequency (RF) electronics can be used. However, these techniques have been limited to measuring coherent sources, such as lasers, due to their inability to disambiguate signals that overlap in the down-converted intermediate frequencies (IF). This excludes most natural sources from being measured. In this manuscript, we present a new dual-comb technique that allows for the measurement of any arbitrary spectrum, even incoherent ones that span multiple comb lines.1, 2 It is shown that using the same equipment required in a dual-comb experiment one can calculate a correlation function between the two channels that has all the information required for accurate reconstruction. We brie y present the theory followed by simulation and an RF comb experiment.
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