Channel power oscillations in an optically amplified wavelength-division-multiplexed (WDM) ring network have been analyzed to reveal the oscillation dynamics and governing parameters of the chaotic behavior. The WDM ring round-trip frequency determined by the closed ring network span length and the speed of the channel power equalizer were found to be the two main factors defining the network stability. Spectral analysis shows that the formerly unresolved chaotic ring network behavior can be understood in terms of mode-locking-like instability which takes a closed WDM ring network as a loss-modulated laser.