Abstract: We investigated the chaotic/hyperchaotic synchronization of two erbium-doped fiber dual-ring lasers using delay injection-feedback. The numerical simulation shows that the two same erbium-doped fiber dual-ring lasers can easily achieve synchronization even though they are chaotic or hyperchaotic only if the delay time and intension of feedback are suitable, even if two lasers are not completely uniform, they also achieve chaotic/hyperchaotic synchronization only if the intension of feedback is suitably added. At the same time, the two lasers show delay synchronization for different delay time, this delay synchronization just account for the delay effect in telecommunication and is available for chaotic secure communication.

Key words: laser physics, delay feedback, erbium-doped fiber dual-ring laser, chaos, synchronization