General analysis of instabilities in erbium-doped fiber lasers

A detailed analysis of a general model of erbium-doped fiber laser dynamics is investigated. Depending upon the parameters the same model describes single-mode cw or self-pulsing lasers, dual-wavelength or bipolarized two-mode lasers. A summary of previous works concerning self-pulsing behavior and antiphase phenomena is presented. The basic physics responsible for the instabilities is the existence of ion clusters in heavily doped fibers. A thorough investigation of the bimode laser equations is performed. Approximate solutions for the steady states and for the second threshold are obtained. The influence of ion-pair concentration (x) on dynamical behavior is studied. In particular, it is demonstrated that optical bistability occurs between 2T- and 3T-periodic orbits versus the pumping rate in the case of intermediate pair concentrations (where T is the fundamental period of the system). The route to chaos is found to be x dependent and of codimension 2. {} 1996 The American Physical Society.