Azimuthal dependence of modal interference in closely spaced single-mode fiber joints

We introduce a closed form expression describing modal interference in closely spaced single-mode fiber joint pairs for operation below cutoff wavelength of the intermediate fiber. The expression shows that modal interference is dependent on the cosine of the azimuthal angle between the lateral offsets of the fiber cores at the two joints. This azimuthal dependence is verified experimentally for operation both below and above the intermediate fiber cutoff wavelength. The result suggests that modal interference in field installable fiber-optic connectors incorporating short fiber stubs can be reduced or eliminated through proper tuning of the lateral offset azimuth.<>