Electrical spectral technique for measuring cross-phase modulation impact in WDM optical systems

An electrical spectral technique to correctly evaluate cross-phase modulation behavior in intensity modulation-direct detection systems is proposed. Intrinsic advantages of the technique, in terms of high accuracy, are discussed in comparison with the classical time-domain method, which requires precise receiver noise characterization. Measures have been performed with a pump-and-probe scheme on different standard optical communications fibers (i.e., G.652, G.655). The employed pump has been intensity modulated by a nonreturn-to-zero alternate pattern at different bit rates (from 1 to 10 Gb/s), with 0.8- and 1.6-nm pump-probe wavelength spacing. The experimental results are compared with the time-domain technique when accurate calibration is performed.