Generation of domain-wall solitons in an anomalous dispersion fiber ring laser

We report experimental observations performed using a net anomalous dispersion Er-doped fiber ring laser without polarization-selective elements,highlighting the domain-wall solitary pulses generated under the incoherent polarization coupling.By adjusting the pump power and the polarization state appropriately,bright and dark solitons can stably co-exist in the cavity,both centered at 1562.16 nm with a 3-dB spectral width of -0.15 nm and a repetition rate of 3.83 MHz.Moreover,the 0.8 mm long thulium-doped fiber(TDF)facilitated the mode-locking and self-starting of the laser.This is the first demonstration of a laser being used to generate bright and dark solitons synchronously while using TDF as the saturable absorber(SA).Except possessing the all-fiber structure,the laser exhibits good stability,which may have a significant influence on improvement of the pulse-laser design,and may broaden practical applications in optical sensing,optical communication,and soliton multiplexed systems.