78 fs all-fiber ring cavity passive mode-locked femto-second laser

All-optical sampling system needs femto-second fiber laser with low time jitter, narrow pulse width and high repetition rate as sampling pulse source. Based on the numerical simulation, passively mode-locked erbium-doped femto-second fiber laser was demonstrated via nonlinear polarization rotation (NPR) effect. The fundamental repetition rate of the fiber laser was 6.028 MHz, the average output optical power was 1.07 mW, the central wavelength was 1570.3 nm, and the spectral width was 33.2 nm, the corresponding Fourier transform limited pulse width of 78 fs was calculated. The average output optical power could be improved by increasing the coupling-ratio of the output optical coupler in the all-fiber cavity. The stability of the fundamental repetition rate of the laser was also measured. The femto-second laser is simple and easy to operate. Furthermore, the laser is compact and portable for the all fiber cavity structure.