An Analytical Model for Performance Estimation in Modern High-Capacity IMDD Systems

In this article, we propose an analytical model to estimate the signal-to-noise ratio (SNR) and then the Bit Error Rate (BER) at the output of a receiver adaptive equalizer in intensity modulation and direct detection (IMDD) optical transmission systems affected by optoelectronic bandwidth limitations, chromatic dispersion (CD), quantization noise, relative intensity noise (RIN), shot noise and thermal noise. We consider that the proposed model is a powerful tool for the numerical design of strongly band-limited IMDD systems using receiver equalization, as it happens in most of modern and future M-PAM solutions for short reach and access systems. We develop the model as an extension of a previously presented one, and then we test its accuracy by sweeping the main parameters of a 4-PAM-based communication system, such as RIN coefficient, extinction ratio (ER), accumulated CD, equalizer type and memory. Our findings show a remarkable agreement between time-domain simulations and analytical results, with SNR discrepancies below 0.1 dB in most cases, for both feed-forward and decision-feedback equalization. Moreover, we tested our model predictions against experimental measurements, confirming its accuracy.