Abstract: A wideband device for measuring the cross-correlation of a first signal and a second signal, includes a first frequency-shifting optical cavity comprising a first frequency shifter designed to shift the optical frequency of the first signal by a first frequency f1 per round trip in the first cavity, the first cavity having a first trip time ?1; a second frequency-shifting optical cavity comprising a second frequency shifter designed to shift the optical frequency of the second signal by a second frequency f2 per round trip in the second cavity, the second cavity having a second trip time ?2; the first and the second optical cavity being designed such that a maximum number of round trips of the first and the second signal in the first and the second cavity is equal to predetermined N, a detector designed to coherently detect the first signal transmitted by the first cavity and the second signal transmitted by the second cavity and generate a photocurrent (Tr) proportional to a luminous intensity detected by th