Novel Method of Generating QAM-16 Signals at 21.3 Gbaud and Transmission Over 480 km

In this letter, we report on a novel method of generating a square quadrature amplitude modulation (QAM-16) signal at 21.3 Gbaud and its subsequent transmission over 480 km. The proposed scheme generates a QAM-16 signal by optically processing a quadrature phase-shift-keying signal using a phase-stabilized fiber interferometer. We also discuss the inherent advantages and limitations of optical and electrical generation methods of QAM-16 signals, and digital signal processing algorithms used in the experiment.