Sensing Bandwidth Enlargement with Ten Orthogonal Codes in Quasi-distributed Acoustic Sensing System

In recent years, quasi-distributed acoustic sensing (QDAS) has attracted lots of attentions and shows great advantages in various fields such as structure health monitoring, intrusion sensing and so on. Sensing bandwidth is one of the essential indexes in QDAS, and there is a trade-off between sensing bandwidth and sensing distance. To break the limitation, the multiple-input multiple-output (MIMO) technology and ten orthogonal codes in the same frequency (OCSF) are utilized as an innovative technology to multiplex the sensing channel in a real-time long-distance QDAS system. In this paper, the sensing bandwidth of QDAS is enlarged to 5 kHz on 99.4 km sensing fiber, which is ten times of that in the conventional QDAS without channel multiplexing; a 4.9 kHz sinusoidal signal is retrieved in real time successfully, with 10 m spatial resolution and 43.8 p epsilon/root Hz noise level.