Silicon 16-QAM optical modulator driven by four binary electrical signals.

We demonstrate a silicon 16-quadrature amplitude modulation (16-QAM) optical modulator. Unlike traditional 16-QAM optical modulator with two Mach-Zehnder modulators (MZMs) driven by two four-level electrical signals, the device is based on four MZMs driven by four binary electrical signals. With the simple electrical driving configuration, the device generates a 16-QAM optical signal at 20 Gbaud with an error vector magnitude of 13.7%.