This is the second part of a special issue on 100G and Beyond: Trends in Ultrahigh-speed Communications. The first part of this special issue contained nine papers written by service providers, telecommunications equipment manufacturers, and top universities and research institutes. This special issue includes comprehensive reviews as well as original technical contributions covering the rapid advances and broad scope of ultrahigh-speed technologies in optical fiber communications. All papers in this issue have been invited. After peer review, five papers were selected to be This is the second part of a special issue on 100G and Beyond: Trends in Ultrahigh-speed Communications. The first part of this special issue contained in papers distributed by service providers, telecommunications equipment manufacturers, and top universities and research institutes. This special issue includes commentary as well as original technical contributions covering the rapid advances and broad scope of ultrahigh-speed technologies in optical fiber communications. All papers in this issue have been invited. After peer review, five papers were selected to be