Theoretical And Experimental Study Of The Ring Cavity Fiber Laser

With the development of optical communication technology, lasers in the optical communication system have to meet the increasing requirement. Fiber lasers, as a device with distinguished advantage, have received great attention from the world. This thesis mainly describes the theoretical and experimental work on Yb³⁺-doped ring cavity fiber laser, Er³⁺-doped ring fiber cavity laser and tunable high power fiber laser. The main contents are shown as follows:1.By means of omitting the ASE and according to the rate equation,We deduced the expressions of threshold value, gain, slope efficiency and output power which belong to the Yb³⁺-doped ring cavity fiber lasers .The characteristics of the Yb³⁺-doped ring cavity fiber laser have been simulated. The relations between performance parameters which contain threshold power, output power and gain and structure parameters which consist of pump power, fiber length, impure chroma, output coupling rate of fiber laser have also been studied. The results show the choose of the structure parameters has important meaning to the optimized design of the laser.2. According to the PSP theory (principal state of polarization, PSP), the mechamism of the tunable fiber laser using the nonlinear polarization technique(NPT) is researched. The relations between the output characters(such as the central wavelength,the tunable bandwidth and the tunable precision)and the parameters of the fiber laser(such as fiber length and polarization angle)are deduced.3.In experiment,we researched a short-cavity ring fiber laser with different fiber length(10cm and 20cm) has been designed and turned out with high concentration Yb³⁺-doped fiber as gain medium. The threshold power of the laser with gain fiber length 10cm is 36.8mW and the other is 39.4mW , and the maximum output power of the laser with gain fiber length 10cm is 21.1mW and the other is 12.7mW.The slope efficiency of the laser with gain fiber length 10cm is 8.2% and the other is 5.1%. Widely tunable ranges as 9.88nm is obtained.4. The output characteristics of Er³⁺-doped ring cavity fiber laser are theoretically studied. Under stationary conditions analytical expressions on output power, threshold pump power and slope efficiency are presented. After that, the output characteristics are simulated numerically combining MATLAB PROGRAMME.5. By means of nonlinear polarization rotation technique and using power amplifier, we studied a high power tunable Er³⁺-doped fiber laser. We achieved a lasing output with continuously tunable wavelength in the range from 1547.70 to 1557.52nm when the pump power of power amplifier is 1.5W and 2.5W. Its optical signal-to-noise ratio and 3-dB spectral width is about 30dBm and no more than 0.1 nm, and the slope efficiency is about 80.1%.