  We present an efficient tool capable of measuring the spectral correlations
between photons emerging from a Hong-Ou-Mandel interferometer. We show that for
our spectrally factorizable spontaneous downconversion source the
Hong-Ou-Mandel interference visibility decreases as the photons frequency
spread is increased to a maximum of 165 nm. Unfiltered, we obtained a
visibility of $92.0 \pm 0.2 \%$. The maximum visibility was $97 \pm 0.2 \%$
after applying filtering. We show that the tool can be useful for the study of
spectral correlations that impair high-visibility and high-fidelity
multi-source interference applications.
