Abstract: Methods for identifying optical fibers which exhibit elevated levels of polarization mode dispersion (PMD) are provided. The methods employ difference traces obtained from optical time domain reflectometer (OTDR) measurements. The presence of a cyclical pattern in such a difference trace has been found to be indicative of a fiber having an elevated level of PMD.

Abstract: The present invention relates to a method of measuring spectral attenuation of an optical waveguide fiber using an OTDR. The spectral attenuation curve is generated by analyzing OTDR data taken at three or four wavelengths. There is particular interest in the wavelength range of 1200 nm to 1600 nm, which includes the operating windows about the wavelengths 1310 nm and 1550 nm. A particularly accurate spectral attenuation curve is obtained using OTDR measurements at 1310 nm, 1410 nm, and 1550 nm.

Abstract: A method for detecting reflection-type discontinuities in an optical waveguide fiber, such as those produced by a fiber break, a contaminant in the glass making up the fiber, a microbend, or a mechanical splice or connector, is provided. The method employs an optical time domain reflectometer (OTDR) and involves cross-correlating an OTDR trace or a modified OTDR trace, e.g., one from which fiber attenuation has been subtracted, with a predetermined waveform which is characteristic of a reflection-type discontinuity. The predetermined waveform can compensate for differences between the noise spectrum of the OTDR trace and white noise. In particular, a predetermined waveform obtained by backward differencing and then forwarding differencing an average of waveforms known to correspond to reflection-type discontinuities is able to provide such white noise compensation.