Device for wide-band spectral analysis of a signal of interest

A wideband device (D) for the spectral analysis of a signal of interest comprising:

• a source(S) designed to generate said signal of interest (Si);
• an optical splitter element (ES) designed to spatially split said signal of interest into a first signal (V1) and a second signal (V2);
• a first frequency-shifting optical cavity (DBDF, BDF1) comprising a first frequency shifter (AOM1) designed to shift the optical frequency of the first signal by a first frequency f1 per round trip in said first cavity, said first cavity having a first trip time τ1;
• a second frequency-shifting optical cavity (DBDF, BDF2) comprising a second frequency shifter (AOM2) designed to shift the optical frequency of the second signal by a second frequency f2 per round trip in said second cavity, said second cavity having a second trip time τ2;
• the first and the second optical cavity being designed such that a maximum number of round trips of said signal in the first and the second cavity is equal to predetermined N;
• a detector (PD) designed to coherently detect the first signal (W1) transmitted by the first cavity and the second signal (W2) transmitted by the second cavity and generate a photocurrent (Tr) proportional to a luminous intensity detected by said detector, a low-pass filter (LP) designed to filter frequencies of the photocurrent that are lower than min (f1/2, f2/2),
• a processor (UT) configured to compute a square modulus of the photocurrent filtered by said low-pass filter, from which a temporal representation of frequency information of said signal of interest is determined, said frequency information being:
• a real part of a fractional Fourier transform of said signal of interest, an order of said fractional Fourier transform being set by the value f1×τ1−f2×τ2 when the first cavity and the second cavity are configured to verify the condition f1×τ1+f2×τ2, modulo 1 or
• a power spectrum of said signal of interest when the first cavity and the second cavity are configured to verify the condition f1×τ1=f2×τ2 modulo 1.