Mechanical and Civil Engineering Seminar

Distributed acoustic and seismic strain sensing with low noise, high spatial resolution, and high dynamic range using un-modified fiber optic cables is now possible. The OptaSense coherent time-domain reflectometry system uses only Rayleigh backscattering of light from the optical imperfections of single or multi-mode fibers to form virtual sensor channels. This system provides 4000 channels at 1 kHz bandwidth for up to 50 km of standard cable for large aperture sensing, or 5000 channels over 5 km of cable at up to a 20 kHz sample rate for precision sensing with full phase coherence among channels. OptaSense is being installed worldwide for security and leak monitoring on oil and gas pipelines and perimeters, and for down-hole sensing in tight gas and carbon sequestration applications replacing standard seismic arrays. In many applications, pre-existing cables that were installed for other uses, such as communications and distributed temperature sensing, can be exploited, thus saving the cost of a dedicated deployment.

Incidental to these primary missions, we have measured the signatures of earthquakes and other natural and anthropogenic seismic and acoustic sources pointing to a myriad of potential new applications. In this talk, we will introduce the technology and show data from example applications. Our goal is to determine if joint efforts between Caltech and QinetiQ OptaSense researchers can contribute to seismic and structural applications, including earthquake early warning and damage assessment systems.