In this paper,we propose a novel and flexible 16-quadrature amplitude modulation(16QAM) transmitter based on cascaded dual-parallel Mach-Zehnder modulator(DPMZM) and phase modulator(PM).The proposed transmitter is able to generate three types of 16QAM signals:square 16QAM,star 16QAM and four-amplitude-four-phase-16-QAM(FAFP-16QAM).The feasibility of the transmitter is verified through experiment,20-Gb/s eye diagrams of the 16QAM signals are obtained.In order to evaluate the performances of the 16QAM signals,simulations are also conducted using VPI Transmission Maker,clear constellations of 40-Gb/s 16QAM signals are achieved by coherent detection.
We propose and numerically demonstrate an ultrafast real-time ordinary differential equation （ODE） computing unit in optical field based on a silicon microring resonator, operating in the critical coupling region as an optical temporal differentiator. As basic building blocks of a signal processing system, a subtractor and a splitter are included in the proposed structure. This scheme is featured with high speed, compact size and integration on a siliconon-insulator （SOl） wafer. The size of this computing unit is only 35 μm × 45 μm. In this paper, the performance of the proposed structure is theoretically studied and analyzed by numerical simulations.
