Phase noise suppression method of DFB fiber laser microphone based on optical reference

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/Hz^1/2. It can be suppressed by more than 32dB at the noise peak, and the suppression effect of the phase noise is very obvious.