A method for measuring fundamental mode cutoff wavelength of single polarization fiber comprising: (i) launching pulsed light of at least one wavelength .lamda..sub.i into one end of the single polarization fiber; (ii) measuring backscattered light intensity corresponding to said wavelength to obtain the backscattered light intensity as a function of fiber position, wherein the backscattered light propagates through the same end of the fiber; and (iii) determining at least one cutoff wavelength and the corresponding position within said fiber for the cutoff wavelength, based on a specified threshold light intensity level.