Coherent optical systems: Principles, contemporary implementations and future challenges for high data rate communication

This paper is a tutorial review for coherent optical communication with emphasis on digital coherent receivers because digital coherent optical receivers are promising solution for next generation optical communication systems. In this paper, principles of coherent communication has been reviewed along with its advantages and prospective modulation formats to achieve 111 Gbps. Digital coherent receivers and their signal processing modules have been reviewed in the light of recent publications and patents. In the end, realization challenges have been addressed from circuit and signal processing point of view.