This thesis mainly focuses on sensor nodes design. A small two-axis and three-axis accelerometer using optic fiber with FBG written in the core as sensing element were originally designed due to the advantages of FBG mentioned above. The proposed design has a concentrated mass sitting in the middle of a rigid frame, and a glass fiber with a FBG written in the fiber core as a stiff spring is connected between each side of the frame and the mass. The two accelerometers can decouple the ground motion along different axes, resulting in virtually zero cross-sensitivity, which exceeds currently available seismometers. The accelerometer or seismometer has a working bandwidth below the structure’s natural frequency and linearly responds to ground movement. COMSOL Multiphysics by using Finite Element Method (FEM) was used to analyze and simulate the two devices.