DAC-Less Amplifier-Less Generation and Transmission of QAM Signals Using Sub-Volt Silicon-Organic Hybrid Modulators

We demonstrate generation and transmission of optical signals by directly interfacing highly efficient silicon-organic hybrid (SOH) modulators to binary output ports of a field-programmable gate array. Using an SOH Mach–Zehnder modulator (MZM) and an SOH IQ modulator we generate ON–OFF-keying and binary phase-shift keying signals as well as quadrature phase-shift keying and 16-state quadrature amplitude modulation (16QAM) formats. Peak-to-peak voltages amount to only 0.27 V
_pp
for driving the MZM and 0.41 V
_pp
for the IQ modulator. Neither digital-to-analog converters nor drive amplifiers are required, and the RF energy consumption in the modulator amounts to record-low 18 fJ/bit for 16QAM signaling.