Theory And Experiment Research Of Two-Stage High Power Er³⁺/Yb³⁺ Co-doped Optical Fiber Amplifier

Infrared laser radiation around 1.5μm is in the low-loss window of fiber communication and of the "eye-safe" attribute. For this reasons, it has widely uses in fiber communication, surgery, remote sensing and so on, which is of great research importance.A fiber amplifier at the wavelength around 1.5μm is studied in this paper. The amplifier consists of two stages, which has an erbium/ytterbium co-doped double-clad fiber amplifier as the second stage. Research details are as follows:In the introduction, principles, history and recent advances of erbium/ytterbium co-doped double-clad fiber amplifier are presented.In theory part, based on rate equations, a theory model including the calculation of ASE powers is built by combining with power propagation equations. For continue wave amplification, the influence of gain fiber length and input signal power's changing on output power is analyzed, the process of optimizing the fiber length and choosing a right input signal power is illuminated in detail too. And then the optimized parameters of the amplifier in simulation are decided. For pulse signal amplification, amplifications of pulse signals with different shapes and repetitions are simulated. Taking rectangle and gauss pulse for examples, the pulse shapes'change after amplification and the influence of repetition's changing on output power, pulse energy and the ASE restrained effect are analyzed.In experiment part, experiments of continue wave and pulse signal are carried out respectively. In the experiment of first stage amplifier, the curves of output powers versus pump powers and the changes of spectrums and pulse shapes after amplifications are measured for continue wave, rectangle signal and sine wave. In the experiment of second stage, amplification of continue wave and Q-switched gauss pulse signal are tested. Several data curves of output powers versus input signal powers for different pump powers are obtained. The spectrums and pulse shapes are measured and analyzed too. Tendencies of powers and pulse shapes'changes noticed in experiment accord with the theory simulations. The highest output power of 1.33 W is achieved in the experiment, which has an optic-optic efficiency of 17 %. The total gain is 29.5 dB.