Adaptive Compensation of Multimode Fiber Dispersion by Control of Launched Amplitude, Phase, and Polarization

In previous work, we studied the compensation of modal dispersion in multimode fiber (MMF) using several different configurations of optical systems that can control the amplitude, phase and polarization of the launched field. In that work, we assumed knowledge of a fiber's principal modes (PMs) and their group delays (GDs), enabling us to compute the optimal settings of the optical system. In practice, however, we do not have prior knowledge of the PMs and their GDs. In this paper, for three of the configurations, we propose algorithms for setting the optical system adaptively, based upon measurements of the eye opening. We present simulations showing that in the absence of noise, the performance of the adaptive solution approaches that of the optimal solution, and characterizing the algorithms' convergence speed and tolerance to noise. We present experiments using a particular configuration and adaptive algorithm, demonstrating their effectiveness in 10-Gb/s transmission through up to 2000 m of 50-μ m-core graded-index MMF.