A dual-frequency-comb spectrometer and a method for spectroscopic investigation of a sample are described. The spectrometer includes first and second frequency comb devices for emitting laser pulses along first and second light paths, wherein the repetition frequency of the laser pulses emitted by the second device is offset from that of the first device. First and second multi-core waveguides including at least two separate single core waveguides having field-coupling via a coupling gap therebetween are arranged in the first and second light paths. The sample is irradiated by the second frequency comb in the second light path. A detector device is arranged in a third light path where the first and second light paths are combined, for simultaneously sensing the first frequency comb and the second frequency comb after an interaction with the sample. A computing device receives output of the detector device and calculates spectroscopic properties of the sample.