A Study of Power Efficiency Maximization in Submarine Cable Systems

Power efficiency is a key concept in submarine cable transmission systems because of fixed and limited electrical power supplies. Electrical power is provided by a DC voltage applied across the cable from power feed equipment (PFE) located at the terminal ends and is used to power all optical amplifiers throughout the entire link which may be many thousands of kilometers. We examine here via system modeling aspects of power efficiency in the context of maximizing this quantity, primarily with respect to the optimal generalized signal-to-noise ratio (GSNR). We explore the dependence on capacity metric, span loss, link length, and fiber attenuation. We also compare the optimal GSNR predicted using pump power as a measure of power consumption in a single fiber with total cable capacity predicted by application of a pump sharing model and the resulting electrical-to-optical conversion efficiency predicted as a function of amplifier output power, span loss, and repeater power available. We find that the cable capacity measure predicts somewhat higher optimal GSNR than the single fiber measure based on amplifier pump power. The optimal GSNR decreases with longer link length and optimal span loss is somewhat higher than previous results based on different analyses.