Impact of dispersion on the output characteristics of an all-fiber Er-doped nanosecond mode-locked figure-eight laser with passive nonlinear optical loop mirror

A mode-locked all-fiber Er-doped laser based on a figure-eight scheme with a passive nonlinear optical loop mirror and pulse duration of few nanoseconds has been realized for the first time. It has been revealed that the main problem of utilization of standard fibers with anomalous dispersion is the propagation of low-energy optical solitons accompanied by nanosecond pulse break up. Herein, the solution to this problem is discussed and stable laser schemes (i.e. all-polarization maintaining) are realized. A strong influence of the total laser dispersion on the nanosecond laser spectral bandwidth has been found.