Real-time coherent optical receivers

The continuous increase of the worldwide data traffic

demands new concepts for data transmission in the

optical fiber-based backbone networks. One promising

way to increase the capacity of the existing fiber

infrastructure is to use quadrature amplitude

modulation (QAM) in combination with

polarization-multiplexing and coherent detection.

In this book all necessary algorithms are presented

that are required for the realization of such a

system using digital signal processing at the

receiver. The main focus thereby lies on the

algorithms for polarization control and carrier

recovery. But also clock recovery, intermediate

frequency control and compensation of intersymbol

interference are considered. The performance of the

algorithms is studied in extensive simulations.

Additionally the results of the real-time

implementation of selected algorithms in a single

polarization and a polarization-multiplexed

synchronous optical QPSK transmission system are

presented. Both systems are the worldwide first that

are realized with a real-time coherent digital

receiver and standard DFB lasers.