Observations of surface deformation are essential for understanding a wide range of geophysical problems, including earthquakes, volcanoes, landslides, and glaciers. More than 1200 Global Positioning System (GPS) stations onshore and five seafloor geodetic stations offshore were installed in Japan [1
]. Additionally, in America, the Plate Boundary Observatory (PBO) plan was founded by the National Science Foundation (NSF) as the geodetic component of the EarthScope project. The PBO consists of a network of 1100 permanent, continuously operating GPS stations, 74 borehole strainmeters, 26 shallow borehole tiltmeters, and six long baseline laser strainmeters [3
]. Since 2012, the Crustal Movement Observation Network of China (CMONoC) was built. Included in the CMONoC are 260 continuous observation stations and 2000 irregular observation stations [4
]. The geodetic technologies used in these three networks, such as GPS, InSAR, borehole and laser strainmeters, provide critical observations of surface deformation and reveal the detailed processes of seismogenic faults. However, the current geodetic technologies are costly and limited in their temporal or spatial resolutions [5
]. Cost-effective and distributed strainmeters are desired for geodic applications. Fiber optic sensors, such as fiber Bragg grating (FBG), represent an opportunity for distributed strain sensing [8
]. However, limited by its silica glass nature, the fiber optic sensor will easily break when it is subjected to large strains (about 10 mε or 1%) and/or a shear force [9
]. Inspired by the FBG sensor, a new coaxial cable Bragg grating (CCBG) sensor was put forward, which is sufficiently robust to survive and operate on large strains, while it holds comparable performances with the FBG sensor, such as distributed sensing, cost-effectiveness, and accuracy [10
]. A cost-effective geodetic strainmeter was designed with dual CCBGs to obtain a lower mixed frequency and minimize environmental noises.