A Distributed Coaxial Cable Strainmeter for Earth Monitoring

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1442623WeiThis grant supports development and testing of a distributed coaxial cable strainmeter that has the potential to offer high accuracy (~ ppm) and high temporal resolution (~1 sec) measurements with unprecedented high spatial (~ 10 m) resolution over kilometers. The concept will rely on tests of coaxial cables that have been imparted with periodic electromagnetic impedance discontinuities (a Bragg grating) which allow for weak reflections of a pulsed input of an electromagnetic wave through the coaxial waveguide or implanted reflectors within the coaxial cable that will enable a coaxial strainmeter based on Fabry-Perot interferometry. A vector network analyzer then is then used to analyze transmission and reflection spectra. The PI would also explore novel signal amplification techniques to reduce losses from returned EM pulses along longer lengths of cable with multiple sensors points along the length of the cable. The potential of the coaxial cable based strainmeter to survive large deformations (5%) and strong lateral collision/impact, may provide valuable and otherwise inaccessible information under certain extreme conditions where fiber optic based strain technologies may fail (e.g., landslides, subglacial deformation, steel structure deformation). The development will engage a graduate student to assist with: 1) development of new modelling methodology for device design and optimization, 2) explore hybrid software-hardware signal processing technology; and 3) build a portable prototype coaxial strainmeter; and 4) characterize the prototype?s performance in the laboratory and in the field.***