Prototyping and Optimization of Ultra-High Speed Fiber Optic Links

摘要

The research was aimed at determining the impact of nonlinearity on the distribution of the differential group delay due to nonlinearity. And at determining the length scale over which polarization mode dispersion (PMD) yields the well-known asymptotic Maxwellian distribution. Professor Kath assisted with both projects. The work in both projects was presented at conferences and is being prepared for publication. In the first project, we simulated a large number of different fibers using parameters that MCI/Worldcom supplied to us. We found that the nonlinearity induces a significant chirp. This chirp can interact with the second-order PMD to substantially affect the final distribution of the differential group delay (DGD). In some cases, it can even reverse the effect of the usual first-order PMD, leading to a 'PMD improvement'. In the second project we solved the Fokker-Planck equation for the evolution of the polarization dispersion vector on the Poincare sphere. We found that the distribution approaches a Maxwellian distribution in approximately 50 correlation lengths. Since this length is only 5 km at most in real fibers, we concluded that the asymptotic distribution will always be observed at the endpoint of real systems. Nonetheless, there is a persistent correlation between the final polarization state and the DGD (length of the polarization dispersion vector). We are working with experimentalists to verify these results.