| Summary: | 博士 === 國立臺灣科技大學 === 電子工程系 === 87 === This thesis presents simple methods to extract system parameters and to analyze the erbium-doped fiber amplifier (EDFA) for the applications of fibers to communications and sensor systems. First, a simple method to determine, in a quantitative way, the degree of the influence of ASE is presented. Through the study of the effect of ASE on EDFA gains, it is and found that the ASE can be neglected when the nearly-no-ASE factor (NNAF) is large enough. It is proposed as an ASE indicator. Furthermore, a formula for computing the error of output power due to the neglecting of ASE in calculation is also presented.
Second, an EDFA parameter extraction method is proposed of obtaining simultaneously the pump absorption cross section, signal emission cross section and signal absorption cross section, the fluorescence lifetime of metastable level, the Er-ion concentration, and the pump and signal absorption coefficients. Based upon the measured dc and ac gains, these parameters can be obtained simultaneously without cutting the fibers or disassembling the EDFA system. They can be computed very easily by the use of our close-form expressions without complicated numerical method. The calculations are in good agree with experimental data.
Then, the close-form expressions of nonlinear Fourier transfer functions are presented for the analyses of distortions and cross modulations in EDFA systems. Based upon Volterra series and the time-dependent perturbation theory, the transfer functions have been obtained after taking account of both the EDFA nonlinearity and chirping effect. Their applications to an AM-SCM and an eight-channel wavelength-division-multiplexed (WDM) systems are demonstrated.
Moreover, the performance of the EDFA system in thermodynamically and electromagnetically harsher environments have been studied. It is found that the SMF-to-EDFA connection suffers the most from temperature effect when the fiber length is not long. The gain variation amounts to -0.023dB/ . Besides, the eletromagnetic interference effect on the photodiode and its light power and wavelength dependences are discussed.
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