A spectrograph to characterize comb spectra

We present a compact echelle spectrograph for characterizing properties of laser frequency combs with large mode spacing, e.g. for astronomical purposes (astro-combs). The spectrograph is inexpensive and easy to build thanks to the use of standard optical components and photographic equipment. Despite its compact dimensions, it features the same resolution as many full-sized spectrographs at astronomical observatories. This is accomplished through the use of a single-mode fiber as a spectrograph input, through which we can conveniently inject the light of an astro-comb.