A novel Mach-Zehnder interferometer (MZI) based on dual antiresonant reflecting optical waveguides (ARROWs) for sensing is proposed. By adjusting the degree of structural symmetry to control the coupling behavior of the dual ARROW, an interferometric sensor without any bending structure can be realized. Operating principles and simulation characteristics of the device are discussed in detail. The refractive-index detection limit of the order of 10/sup -5/ is achieved.