Parallel sensing and demodulation systems for acoustic waves based on dual optical frequency combs

A parallel sensing and demodulation system for acoustic waves based on dual optical frequency combs, comprising:

• a first optical frequency comb, a tunable filter, a fiber optic Fabry-Perot interferometric sensor array, a first fiber optic coupler, a second optical frequency comb, a second fiber optic coupler, an optical pre-amplifier, a fiber optic attenuator, a photodetector, a data acquisition card, and a computer, wherein,
• the tunable filter is configured to use a pulse sequence of the first optical frequency comb as an incident light source for wavelength selection, split the incident light source into m beams of light, and input each of the beams of light into a corresponding fiber optic Fabry-Perot interferometric sensor of the fiber optic Fabry-Perot interferometric sensor array, respectively;
• each of the beams of light consists of comb peaks with three different wavelengths
• m
• ∈
• 1
• ,
• ⌊
• min
• ⁢
• {
• f
• r
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• 1
• ,
• f
• r
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• 2
• }
• Δ
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• f
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• m
• ≤
• N
• ;
• wherein fr1 denotes a repetition frequency of the first optical frequency comb, fr2 denotes a repetition frequency of the second optical frequency comb, Δfr denotes a difference in repetition frequency between the first optical frequency comb and the second optical frequency comb, N denotes a count of comb peaks of the first optical frequency comb, the difference in repetition frequency Δfr=|fr1−fr2|>2fa, wherein fa denotes a frequency of an acoustic wave signal;
• the repetition frequency fr1 of the first optical frequency comb and the repetition frequency fr2 of the second optical frequency comb are in a range of 20 GHz to 500 GHz;
• the fiber optic Fabry-Perot interferometric sensor array includes m parallel branches, each of the branches includes a fiber optic circulator and the fiber optic Fabry-Perot interferometric sensor, a Fabry-Perot cavity of the fiber optic Fabry-Perot interferometric sensor is configured to receive the acoustic wave signal;
• the fiber optic Fabry-Perot interferometric sensor array is configured as follows:
• each of the branches corresponds to each of the beams of light, each of the beams of light is injected into the fiber optic Fabry-Perot interferometric sensor from a first port of the fiber optic circulator, and a demodulated interferometric optical signal that changes in light intensity as the Fabry-Perot cavity receives the acoustic wave signal is output through a third port of the fiber optic circulator;
• the first fiber optic coupler is configured to couple the demodulated the interferometric optical signal output from each of the branches of the fiber optic Fabry-Perot interferometric sensor array to form a merging beam of light;
• the second fiber optic coupler is configured to couple the second optical frequency comb with the merging beam of light;
• the optical pre-amplifier is configured to amplify an optical signal coupled by the second fiber optic coupler;
• the fiber optic attenuator is configured to regulate an optical power of an optical signal amplified by the optical pre-amplifier;
• the photodetector is configured to obtain an analog electrical signal by detecting a beat frequency signal output from the fiber optic attenuator;
• the fiber optic Fabry-Perot interferometric sensor array is further configured to number comb peaks of the first optical frequency comb and the second optical frequency comb, with a pumping optical comb peak being numbered as 0 and comb peaks whose frequencies are smaller than the pumping optical comb peak being numbered as −1, −2, . . . , −N+1, −N, and comb peaks whose frequencies are greater than the pumping optical comb peak being numbered as 1, 2, . . . N−1, N;
• frequencies of a n-th comb peak of the first optical frequency comb and the second optical frequency comb peak are denoted as fn1=f01+nfr1 and fn2=f02+nfr2, respectively, and n∈[1, N];
• f01 denotes a center frequency of the first optical frequency comb and f02 denotes a center frequency of the second optical frequency comb;
• and Δf0 denotes a difference in center frequency between the first optical frequency comb and the second optical frequency comb;
• and an intensity of the first optical frequency comb is demodulated based on the acoustic wave signal received by the fiber optic Fabry-Perot interferometric sensor array, and a frequency of an intensity-demodulated signal is fn1±fa, wherein fn1=f01+nfr1;
• the second fiber optic coupler is further configured to couple the intensity-demodulated signal with the second optical frequency comb, and a frequency of the second optical frequency comb is denoted as fn2, wherein fn2=f02+nfr2;
• the data acquisition card is configured to acquire a coupled signal to:
• obtain a set of intensity-demodulated signals with a center frequency of Δf0±mΔfr and a sideband of fa, i.e., (Δf0±mΔfr)±fa, wherein Δfr=|fr1−fr2|≠0, and convert the analog electrical signal outputted by the photodetector into a digital signal and transmit the digital signal to the computer;
• and
• the computer is configured to perform a three-wavelength adaptive demodulation data processing on the digital signal.