Study of an Er-Doped All-PM-Fiber Laser Mode- Locked by Nonlinear Polarization Evolution

We demonstrate an erbium-doped all-fiber laser mode-locked by means of nonlinear polarization evolution in polarization maintaining (PM) fibers. The artificial saturable absorber consists of a piece of PM active fiber and a Faraday mirror (FM) in combination with angle splice. The birefringence of the PM fiber is compensated, and the slope of transmission curve is steepened thanks to the FM and the active fiber. The transmission characteristics demonstrate that the active fiber is a crucial factor to obtain a high repetition rate ultrafast laser. We study and discuss channeled spectra caused by the mechanisms of soliton-soliton interaction and birefringence-induced filter. A good agreement is achieved between the theoretical analyses and experimental results.