Study On The Acousto-Optical Tunable Er～(3+)-Doped Fiber Laser

Wavelength-Division-Multiplexing(WDM) technology is an effective approach to increase the capacity of fiber communication system. And now it is an international progress direction of fiber communication technology. Tunable laser and wavelength filter are two kinds of key devices in WDM fiber communication system, and tunable laser is used in the fields of coherent communication, fiber sensor and spectrum analysis as well.Tunable erbium-doped fiber laser(EDFL) using an integrated optics acousto-optical tunable wavelength filter(AOTF) is studied, which has many advantages such as wide tunable range, narrow linewidth, quick tuning speed, easy and reliable tuning and compatible with fiber system. So it is just fit for WDM fiber communication.The research is composed of three main parts: 1.manufacture of acoustooptical tunable filter(AOTF); 2.theoretical and experimental research on tunable Er3+-doped fiber laser; 3.realization of single mode narrow linewidth Er3+-doped fiber laser and the theoretical analysis of delayed self-heterodyne/homodyne methods. Derived from rate equations and propagation equations, the output characteristic of Er3+-doped fiber ring laser is studied in details. A novel linear configuration Er3+-doped fiber laser is presented by considering the specialities of AOTF and the saturable absorber. Two stages of quasi-collinear acoustooptical tunable filters which share the same acoustic waveguide and IDT are acted as the tuning elements which ensure that the central wavelengths are consistent with each other. Here, AOTFs also play the roles of frequency shifters and polarimeter to eliminate the spatial hole burning effect of linear cavity laser and make the output light is polarized. An unpumped Er3+-doped fiber(low dopant) which used as the transient grating is inserted in the cavity to narrow the linewidth. Good experimental results were achieved in ring fiber laser by using the single stage AOTF and EDFA.