Study Of Frequency-difference Tunong Techniques For Dual-wavelength Single-longitudinal-mode Erbium-doped Fiber Laser

With the rapid development of fiber optics and laser techniques,fiber laser has become one of the hot spots of laser.As a member of them,dual-wavelength single-longitudinal-mode erbium-doped fiber laser has wide applications in the fields of laser measurement,etc.The dual-wavelength single-longitudinal-mode erbium-doped fiber laser can provide light sources for absolute distance measurement,which can generate the synthetic wavelength of different length by tuning the frequency difference,and then can greatly improve the measurement accuracy.Therefore it is of great significance to design and study the tunable two-wavelength single-longitudinal-mode erbium-doped fiber laser.In this thesis,the experimental investigations had been done for the dual-wavelength single-longitudinal-mode erbium-doped fiber laser,a wavelength-tuning device has been designed based on an equal-strength cantilever beam,and its feasibility has been experimentally verified.The main contents of this thesis are included as follows:Firstly,the research situation of dual-wavelength single-longitudinal-mode fiber laser and the fundamental principles as well as the main features of fiber laser have been briefly introduced.Secondly,both a system and its operating principle of dual-wavelength single-longitudinal-mode erbium-doped fiber laser based on fiber polarizing beam splitter have been introduced.The laser characteristics have been studied experimentally.including the output power,oscillating mode,and so on.The research results have shown that the fiber laser can output orthogonally and linearly polarized dual-wavelength single-longitudinal-mode laser,the wavelengths of which are 1539.93nm and 1550.12nm,respectively.Finally,the sensing characteristic of fiber Bragg grating(FBG)and the variations of central wavelength with both stress and temperature have been theoretically analyzed.A device based on equal-strength cantilever beam for wavelength tuning has been designed,and the parameters have been determined by using the software of ANSYS.The experimental system of the wavelength interval tuning of two FBGs has been set up and implemented.The differential the wavelength interval tuning of two FBGs has been set up and implemented.The differential tuning of the wavelength interval has been realized by changing the displacement of the cantilever free end.The tunable range from 8.856nm to 10.996nm has been observed experimentally,and the wavelength difference varies linearly with the displacement applied to the free end of the cantilever beam,and the tuning sensitivity is 0.238nm/mm.In conclusion,the frequency-difference tuning scheme for the two-wavelength single-longitudinal-mode erbium-doped fiber laser in this thesis has been feasible,which has the advantages of wide tuning range,light weight,small volume.It has laid the solid foundation for the further studies of frequency tuning,laser frequency stabilization and interferometric measuring techniques,and therefore it has great reference value.