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

Tunable fiber laser is not only an important kind of device in wavelength-division-multiplexing fiber communication system, but also can be used in the fields of coherent communication, fiber sensor and spectrum analysis. Tunable erbium-doped fiber laser using an integrated optics acousto-optical tunable wavelength filter is studied, which has many advantages such as wide tunable range, narrow line width, quick tuning speed, easy and reliable tuning and compatible with fiber system. The research which is the important part of the tunable erbium-doped fiber laser is composed of two main parts: 1. the gain part of the tunable erbium-doped fiber laser, which in fact is an erbium-doped fiber amplifier, its output characteristics are discussed both in theory and experiment, and the differences are also discussed between theory and experiment; 2. the saturated absorber part of the tunable erbium-doped fiber laser, also the part to narrow the line width of the fiber laser. The line-width narrowing mechanism in fiber laser induced by unpumped Er-doped fiber is presented from the aspect of coupling wave equation, and the main factor is considered as the standing wave induced by interference. The line-width is narrower when the standing wave is stronger, and the narrowing effect disappears with the disappearance of the standing wave. In the experiment, when adding a Faraday mirror in the laser cavity to remove the standing wave , the narrowing effect disappears. So the theory is proved by the result of the experiment.