Effects of signal power control strategies and wavelength assignment algorithms on circuit OSNR in WDM networks

Software-defined networking is enabling wavelength-division multiplexed (WDM) networks to be programmable down to individual components. While taking into account typical gain and noise figure profiles of erbium-doped fiber amplifier (EDFA) components, the authors consider a number of signal power control strategies and compare their performance in terms of achievable lightpath optical signal-to-noise ratio (OSNR). These strategies are applied network-wide to concurrently control the gain of each individual amplifier and the signal power equalization at each reconfigurable optical add/drop multiplexer. Simulation and (in part) experimental results show that the lightpath OSNR is affected by three factors: the EDFA gain control strategy, power equalization strategy and wavelength assignment (WA) algorithm. A trade-off between lightpath average OSNR and OSNR variance across the WDM channels is also noted. Experimental work is conducted using a five-node meshed WDM network testbed proving both feasibility and effectiveness of a coordinated use of signal power control strategies and WA algorithms.