Modelling Nonlinearities in RF Photonic Links

We introduce an idealized model of a photonic link comprised of a Mach-Zehnder modulator, described by sinusoidal nonlinearity, and a photodiode, with a memoryless nonlinearity described by a Taylor expansion about the operation point. The model uses an unconventional expansion that simultaneously, versus sequentially, incorporates both modulator and photodiode nonlinearities, truncates naturally at the order of the photodiode nonlinearity, and gives a simple closed-form expression for those expansion coefficients. We illustrate the model's utility by extending an earlier analysis of a predistortion technique.