Abstract

Fiber ring lasers using erbium-doped fibers as gain media have attracted much attention recently because of their simple structures and rapid progress in erbium-doped fiber technology. We theoretically study a fiber ring laser that consists of a few kilometers of fiber, a delay stage, a polarization controller, an isolator, a Fabry-Perot interferometer, an Er-doped fiber amplifier, and an output coupler.¹ When loss is compensated by gain, solitons propagate. The repetition rate is set by the fiber Fabry-Perot interferometer. The fiber is modeled by the nonlinear Schrodinger equation and the fiber Fabry-Perot interferometer by a comb filter in the frequency domain. Our numerical simulations show that a pulse train will not self-start unless a saturable absorber is introduced and a frequency limiter is present. A possible source of the saturable absorption is the combined effect of cross-phase modulation in the fiber and polarization sensitive components in the ring structure.

© 1991 Optical Society of America