All-Optical Wavelength Conversion And Mode-Locked Fiber Laser

This dissertation is focused on nonlinear optical loop mirror based all-optical wavelength conversion technology and passively mode-locked fiber laser. The main points are as follows:The switching characteristics of nonlinear optical loop mirror are theoretically analyzed, and the mechanism of all-optical wavelength conversion technology based on nonlinear optical loop mirror is introduced in detail. The expressions of optimal peak power of control pulse and initial time delay between control pulse and probe pulse are demonstrated. It is also, the influences of walk-off effect, the length of loop, the initial time delay and peak power of control pulse on the shape of output signal are numerically analyzed. The results show that the walk-off between control pulse and probe pulse plays an important role in all-optical wavelength conversion based on nonlinear optical loop mirror.With a nonlinear optical loop mirror serving as the saturable absorber, mode-locking is realized in the figure-of-eight cavity Er-doped fiber laser. When the laser is pumped at 100mW, stable, self-starting 432ps mode-locked pulse centered at 1561nm with 10nm bandwidth and 0.57nJ energy is successfully obtained at the repetition rate of 1.1MHz. Meanwhile, experimental study of the wavelength tunable passively mode-locked Er-doped fiber laser based on figure-of-eight cavity is presented. Wavelength tunable and stable mode-locked pulse is achieved by utilizing tunable fiber grating filter. On the condition that the pump power of Er-doped fiber amplifiers is fixed, by adjusting the tunable filter and orientation of polarization controllers, the mode-locked pulses with average output power fluctuation less than 0.8dBm, and tunable range from 1548nm to 1570nm are obtained.