The impact of attitude deformation of towed linear array and the fitting error of point attitude sensors on beamforming. We studied All-fiber acoustic-posture integrated towed linear array based on distributed feedback fiber laser (DFB-FL) hydrophone and optical frequency domain reflectometry (OFDR) distributed attitude measurement. Analyzed the principle of towed array direction finding, and the influence of towed array attitude deformation on directional error was analyzed. Designed an 8-element hydrophone towed linear array structure with a diameter of 16mm, effectively combining fiber laser hydrophones with attitude sensing multi-core optical fiber. Finally, the effectiveness of attitude correction was verified through static direction finding experiments in anechoic tank, and the accuracy of direction finding was better than 2° under the extreme "S-bend" shape conditions of the drag array attitude. It can effectively improve the accuracy of direction finding.
In order to reduce the phase noise introduced by the unbalanced interferometer in the distributed feedback (DFB) fiber microphone modulation system, a phase noise compensation method based on a stable laser source as an optical reference is proposed. The narrow linewidth laser source is incident on the unbalanced Michelson interferometer shared by the microphone, so that it has the same optical path difference. This optical phase noise information is used to offset the noise introduced by the interferometer, so as to achieve the purpose of noise suppression. The principle of the unbalanced interferometer composition and suppression are theoretically analyzed and experimentally verified. The experimental results show that under the quiet conditions of the laboratory, compared with the structure that has not been suppressed, the noise of the microphone primitive is reduced from about ± 0.2rad to within ± 0.04rad, the power spectral density is reduced to less than -58.95dB/Hz1/2. It can be suppressed by more than 32dB at the noise peak, and the suppression effect of the phase noise is very obvious.
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