Consideration is given to a new optical fiber technique for the measurement of the spatial distribution of physical fields (e.g., magnetic field, electric field, temperature, mechanical stress): polarization-optical time domain reflectometry (POTDR). The technique relies upon the time resolution of light backscattered from a pulse propagating in a monomode optical fiber to measure the spatial distribution of the fiber's polarization properties. These properties are modified by the field under investigation. The technique appears feasible and could form the basis for a new measurement technology.