| With the development of fiber-optic communication system, the transmission rate of the networks has reached a high level. By contrast, in the nodes of optical networks, optical-electrical-optical transformation, which is much slower, is still required to perform optical signal processing, including wavelength conversion,3R regeneration and complex optical logic gates etc. Consequently, all-optical signal processing technology is used to increase the signal processing speed and reduce the total energy consumption with the absence of optical-electronic transformation, so it is the the key technique in the next generation fiber-optic communcation system.Semiconductor optical amplifier (SOA) is one of the most promising devices widely used in all-optical signal processing system, thanks to its high nonlinearity, small size, potential for integration, low power consumption and low cost. The application of cross gain modulation (XGM), cross phase modulation (XPM) and transient cross phase modulation (T-XPM) in SOA have been comprehensively investigated, which is corresponding to carrier recovery time, linewidth enhancement factor (LEF) and linewidth enhancement factor due to carrier heating (CH) respectively. Based on the theoretical study and numerical simulation of the mechanism in SOA, this thesis has measured the three key parameters in SOA. In summary, the main research achievement and contribution are as follows:(1) The basic principle of ultrafast process in SOA and the theory of propagation of light in the medium of SOA are investigated. The ultrafast nonlinear effects and their application are discussed. The evolution of the models that study the nonlinear process in SOA is summarized, and the applicable situation is given. Then the three key nonlinear processes (XGM, XPM, T-XPM) and the corresponding applications, including the related parameters in SOA are given. And then the theory of the Kramers-Kronig (K-K) relations which account for the calculation of linewidth enhancement factor is derived. The relationship between K-K relation and linewidth enhancement factor is described. At last, the theory about the contribution of ultrafast effect to the conversion efficiency of four-wave mixing (FWM) is derived.(2) A scheme of measurement of the carrier recovery time of SOA based on dual pump four-wave mixing (FWM) technology is proposed and experimentally realized, which needs simply configuration. The results are polarization independence. And because it come from the measurement for the beat signal, the result is highly accurate.(3) A scheme of the measurement of the carrier recovery time of SOA based on narrow band amplified spontaneous emission (ASE) FWM technology is present. This configuration is much simpler, and the procedure is very simple and convenient. Only one measurement is necessary, but the conversion efficiency of FWM at a large range of wavelength can be obtained. What's more, the result is reliable by the comparison to the nominal value.(4) Some of the approaches to measure the LEF are reviewed. The characteristic for each approach is analyzed, including the configuration of the experiment and the precision and accuracy of the results. And then we measured the LEF of the SOA sample using K-K relation and shift of ASE spectra at different injected currents, respectively.(5) A method to measure the LEF due to CH is given. The simulation of the contribution of the CH effect to the conversion efficiency of FWM based wavelength conversion is studied. The difference between the positive detuning and negative detuning of the probe light and the probe light is discussed. The results can be got from the fitting to measured results.
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