Real-time Digital Carrier & Data Recovery for a Synchronous Optical Quadrature Phase Shift Keying Transmission System

Abstract — This paper focuses on the recent progress in coherent optical communication using advanced digital signal processing (DSP) technology. In particular the design of DSP components is presented which are required to realize a 10 Gbaud synchronous optical quadrature phase shift keying (QPSK) transmission system. Additionally the measurement results of a preliminary synchronous QPSK transmission setup with distributed feedback (DFB) lasers and real-time digital in-phase and quadrature (I&Q) receiver at a data rate of 1.4 Gbit/s are shown. The minimum bit error ratio (BER) was 1.7·10-5, lower than ever reported before for a real-time system with DFB lasers. Index Terms — Optical communication, quadrature phase shift keying, synchronous detection, real time systems, digital integrated circuits. I