Nonlinear Distortion in a Silicon Microring-Based Electro-Optic Modulator for Analog Optical Links

We analyze silicon microring modulators for analog signal generation, in terms of harmonic and intermodulation distortions. Free carrier plasma dispersion effect in silicon, Lorentzian-shaped resonance profile, and cavity photon lifetime are identified as the sources of modulation nonlinearity. Simulations show that the silicon microring modulators exhibit good modulation index and carrier-to-distortion ratio (CDR). For the generation of 10-GHz suboctave analog signals, a high optical-modulation-index of up to 46%, a CDR of 57 dB, and a spurious free dynamic range of 96 dB can be obtained. In fiber transmission, the microring-generated signal CDR can be improved by 10 dB due to the interaction between frequency chirp and chromatic dispersion.