Research On Sound Detection Optimization Based On Distributed Fiber Sensing Technology

Distributed optical fiber acoustic sensing(DAS)is an important part of the field of optical fiber sensing.Compared with traditional electronic acoustic sensors,DAS has the advantages of anti-electromagnetic interference,long sensing distance,large sensing bandwidth and dense sensing points.Phase-sensitive optical time domain reflectometry(Φ-OTDR)is an important sensing technology in DAS,which has broad application prospects in voice monitoring,perimeter security,seismic wave detection and other fields.In speech detection and other fields,two main problems have been widely concerned in recent years: the response sensitivity of single-mode fiber(SMF)to speech signals is insufficient,and the noise interference is serious,resulting in poor speech signal quality;Φ-OTDR has the problem of huge data volume,resulting in slow demodulation speed,which causes difficulties in real-time and offline processing.In view of the above two problems,this thesis makes corresponding solutions.The main contents of this thesis are summarized as follows:1.The principle of the distributed optical fiber acoustic sensor system is introduced.The principle and performance parameters of Φ-OTDR systems are described,the principle difference of the pulse compression Φ-OTDR system is analyzed,the performance of the traditional Φ-OTDR system is compared,and the demodulation scheme selected in this thesis is expounded.2.A speech enhancement system based on pulse compression Φ-OTDR is proposed.In order to improve the response sensitivity of optical fiber,the optical fiber is wrapped around the sensitized unit as an optical fiber microphone.In the case of a single optical fiber microphone,a single-channel speech enhancement system based on pulse compression Φ-OTDR and OM-LSA is proposed,which effectively improves the quality of the speech signal.In the case of multiple optical microphones,a multi-channel speech enhancement system based on pulse compression Φ-OTDR,GSC beamforming technology,and a multichannel OM-LSA post-filtering algorithm is proposed,which further improves the quality of the speech signal.A horizontal comparison between the noise reduction algorithms used in distributed optical fiber sensing and the proposed system proves the excellent performance of the system.3.The CUDA-based pulse compression Φ-OTDR phase demodulation system is implemented.This thesis introduces the basic framework structure of GPU and the basic principle of CUDA programming.The phase parallel demodulation program of pulse compression Φ-OTDR is implemented,and the experimental data is modulated,which reflects the accuracy and high efficiency of the scheme.Real-time phase demodulation is realized by setting reasonable system parameters.The distributed optical fiber sensing sound pickup system proposed in this thesis has great improvements in phase demodulation speed and speech signal quality,which provides a new possibility for practical and high-quality DAS systems.