Generation of Square or Hexagonal 16-QAM Signals Using a Dual-Drive IQ Modulator Driven by Binary Signals

We propose a simple square or hexagonal 16-QAM signal generation technique using a commercially available dual-drive IQ modulator driven by four binary electrical signals with properly designed amplitudes. We analytically derive the required driving signal amplitudes for square and hexagonal 16-QAM and characterize its implementation penalty. Polarization-multiplexed (PM)-16-QAM signals at 28 Gbuad are experimentally demonstrated and stable performance is achieved with simple bias control.