Real-time coherent optical receivers

The continuous increase of the worldwide data trafficdemands new concepts for data transmission in theoptical fiber-based backbone networks. One promisingway to increase the capacity of the existing fiberinfrastructure is to use quadrature amplitudemodulation (QAM) in combination withpolarization-multiplexing and coherent detection. In this book all necessary algorithms are presentedthat are required for the realization of such asystem using digital signal processing at thereceiver. The main focus thereby lies on thealgorithms for polarization control and carrierrecovery. But also clock recovery, intermediatefrequency control and compensation of intersymbolinterference are considered. The performance of thealgorithms is studied in extensive simulations.Additionally the results of the real-timeimplementation of selected algorithms in a singlepolarization and a polarization-multiplexedsynchronous optical QPSK transmission system arepresented. Both systems are the worldwide first thatare realized with a real-time coherent digitalreceiver and standard DFB lasers.