A fiber optic interferometric position sensor and measurement method thereof suitable for determining the moving direction of a measurement object in an environment of high electric or magnetic field strengths are disclosed. These nanomaterials are in the form of nanofibers, nanowires, nanorods, nanoscrolls andor nanotubes. In particular, the relationship between the allowable temperature difference and the diameter of seed crystal is preset so that the temperature difference between the seed crystal at the time the seed crystal is immersed in the melt and the melt falls within the allowable temperature difference at which dislocations are not introduced into the seed crystal. At least a portion of the active optical element is exposed to a working fluid within a vapor tight chamber of the heat transfer mechanism.