Transponder Implementation Penalty-Accounted Gaussian-Noise-Based Performance Modeling of Fiber-Optic Transmission Systems

In this article we describe an analytical model for estimating performance degradations caused by non-ideal transponder implementation for coherent modulation formats based on parametric fitting of back to back measurements. We discuss in detail several reasons for implementation penalties (IP) such as noise in the transmitter and the receiver, non-ideal filtering, and quantization in the analog-to-digital converter, and how the fitting parameters depend on these penalties. We consider how to combine the IP model and the Gaussian noise (GN) model of nonlinear propagation which includes Amplified Spontaneous Emission (ASE) and Nonlinear Interference (NLI) noise impacts. We modify the Signal to Noise Ratio (SNR) expression of the GN model to include any performance impairments from a non-ideal transponder and additional link components apart from the transponder. In this article we consider transponders based on 16QAM and 2ASK/4PSK-8QAM modulation formats. Then we compare the modeling results obtained with the IP and GN models with experimental data for erbium doped fiber amplifier (EDFA) and Raman-assisted transmission systems. We find that this modeling approach demonstrates good agreement experiment data.