Er~ ( 3+ ) /yb~ ( 3+ ) Study On High - Power Double - Clad Fiber Amplifier

Fiber amplifiers with high-power, wide-gain band and low-noise figure are required for applications to DWDM systems, fibre CATV system and space optical communication system. Ultrahigh-power, ultra-wide band and optimal parameters are becoming the goals the fibre amplifier pursues for and the focus both at home and abroad. Based on the characteristics of double-cladding fibre's configuration, the amplifier with high-power output at 1.55 μmis manufactured by using the cladding-pumped coupling technique. In this dissertation, the double cladding Er3+-Yb3+ co-doped fiber amplifiers is designed and optimized through theoretical analysis at first. Using the relaxation method and Runge-Kutta method to solve the rate and power propagation equations of amplifiers, the output signal power, gain and noise characteristics of double cladding Er³⁺-Yb³⁺ co-doped fiber amplifiers pumped at 975nm are investigated numerically. Their varyings as functions of the active fiber length, input pump power and input signal power are described. Based on the analysis of conventional kinds of cladding-pumped coupling techniques, an overview on their key problems is given. The method, etching gratings on the inner cladding to achieve the side cladding-pumped coupling, is proposed. The efficiency of waveguide gratings coupling is calculated by using the theory of waveguide gratings coupling. To solve the problems of which the wavelength of pump lasers and the peak absorption area of fibers are not at the same fields, we carried out the way of temperature-tuned and controlling current injection to have the pump laser's wavelength tuned and locked, also made its operating wavelength close to 975nm which attributed to Yb³⁺ ion absorption peak. The techniques of thermo-electronic cooling and pulse width modulating were used to establish a critical temperature controlling system for LD, which caused the pump laser's wavelength stability to stay in the range of 0.3nm. The experiment measured the major functional parameters of the amplifier when it was used in the single-stage and cascade conditions. Working in the single-stage amplifying condition, the small-signal gain at 1552nm was more than 30dB with Ps=-15dBm and Pp=3W. The noise figure reached 5.2dB. When input signal power was 5dBm and also at the same pump power, the large-signal gain and noise figure...