DISTORTION RELATED TO POLARIZATION-MODE DISPERSION IN ANALOG LIGHTWAVE SYSTEMS

Analog transmission in single-mode fiber using chirped sources gives r ise to nonlinear distortion when polarization-mode dispersion (PMD) is present. We investigate experimentally and theoretically two mechanis ms for this distortion: for chirped sources, PMD in the presence of po larization-mode coupling results in second-order distortion that is pr oportional to the square of the modulation frequency; when polarizatio n-dependent loss is present, an additional second-order distortion ter m occurs that is independent of modulation frequency. Both mechanisms give rise to distortion that is time varying due to the sensitivity of PMD to ambient temperature changes. Numerical examples indicate that these effects can limit the capacity of analog systems that use direct ly modulated semiconductor lasers.