Distributed Acoustic Sensing With Sensitivity-Enhanced Optical Cable

Fiber-optic distributed acoustic sensing (DAS) technology has many outstanding advantages, such as long sensing range, high detection efficiency, wide frequency response, low operation cost, long working lifetime, et al. It can be anticipated that DAS has great potential to become a next generation technology of long-distance vibration and acoustic wave detection in the future. However, despite the rapid development of DAS technology, the sensitivity of optical cable is still a main limitation in terms of the applications of DAS technology. In this paper, we propose and demonstrate a sensitivity-enhanced optical cable with smaller diameter, lighter weight, and greater flexibility than conventional cables. This novel cable is experimentally tested both in lab and field. The results show that the acoustic sensitivity of the cable has been significantly improved by ~10 times, comparing with a rigid cable that has much higher reflection and attenuation of acoustic waves. Hence, such a sensitivity-enhanced cable could be one of the best candidates for DAS applications as a general sensing cable. In addition, we found that the experimental results are in agreement with our theoretical analysis, providing a guidance for design of sensitivity-enhanced cables. Finally, this cable has been successfully demonstrated in the field test of borehole vertical seismic profiling (VSP), and good performances have been achieved. The perfect combination of sensitivity-enhanced cables and high-performance DAS systems would provide a powerful tool for many DAS applications.