Simulation of generation of ultrashort pulses in a laser based on the nonlinear polarisation evolution in two segments of a polarisation-maintaining fibre

A model describing generation of ultrashort optical pulses in a fibre cavity with Kerr nonlinearity and normal dispersion is constructed based on numerical solution of a nonlinear Schrödinger equation. The model makes it possible to investigate the specific features of pulsed generation of a passively mode-locked laser based on the effect of nonlinear polarisation evolution (NPE) in two segments of a polarisation-maintaining (PM) fibre. It is shown theoretically that the proposed scheme may provide generation of linearly chirped optical pulses with a spectral width of above 25 nm and a centre wavelength of 1030 nm.