Wide-band device for measuring the cross-correlation of signals

A method for measuring the cross-correlation of a first and a second signal (Si1, Si2) using a first frequency-shifting optical cavity (BDF1) having a first trip time τ1 and a second frequency-shifting optical cavity (BDF2) comprising a second frequency shifter (AOM1) having a second trip time τ2, a maximum number of round trips of the first signal and of the second in the first and the second cavity being equal to predetermined N, said method comprising the following steps:

• F. generating said first signal s1(t) and said second signal s2(t);
• G. injecting said first signal into the first frequency-shifting optical cavity (BDF1) and shifting the optical frequency of the first signal by a first frequency f1 per round trip in said first cavity, injecting said second signal into the second frequency-shifting optical cavity (BDF2) and shifting the optical frequency of the second signal by a second frequency f2 per round trip in said second cavity;
• H. coherently detecting the first signal transmitted by the first cavity and the second signal transmitted by the second cavity and generating the photocurrent (Tr) proportional to the detected luminous intensity, a maximum number of round trips of the first and the second signal respectively in the first and the second cavity before they are transmitted being equal to predetermined N, and
• I. filtering frequencies of the photocurrent that are lower than
• min
• ⁡
• (
• f
• 1
• 2
• ;
• f
• 2
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• ,
• J. computing a Fourier transform of said filtered photocurrent, so as to generate an output signal (SS) that is representative of a real-time cross-correlation between the first signal and the second signal, C(T)=s1(t)s2*(t−τ, with τ=n(τ1−τ2), n∈[1, N].