Study And Application Of Nonlinear Optical Coupling Transmission And Switching Characteristics

Since the 1990 s, human society has entered into the time with the information exchange growing rapidly, which is never happened. The communication has become an important part of people’s life. It leads to the frenzied growth of the global communication service and the data communication service. And greater demands have been placed on the ability of transmission in communication network. In the case of the shortage of traditional communication network, the new All Optical Network has come across. As the important part of All Optical Network, the optical fiber coupling technique has been the research hotspot recently and the switching characteristic has been key technology in the All Optical Network. The paper focuses on the nonlinear optical coupler which is based on coupling technique. It discusses and investigates the switching and transmission characteristic in two-core coupler and three-core coupler.At first, it introduces the concept of Maxwell equations and the basic theory of optical pulse transmission in detail. Like all the electromagnetic phenomena, the optical field transmission in fiber is also subject to the Maxwell equations. Starting from the Maxwell equations, it gives the wave equation of optical pulse propagation in optical fiber, and the nonlinear Schr?dinger equation(NLSE) is deduced, which is followed by the pulse transmission in fiber. Based on NLSE, the coupled-mode equations are demonstrated in detail. According to different experimental conditions, the coupled-mode equations need to be modified properly. And the split-step Fourier method(SSFM) is given, which is the numerical solution of coupled-mode equation.Secondly, the soliton pulses propagation and switching in two-core nonlinear fiber couplers are investigated, using the split-step Fourier method(SSFM). It gives a detailed discussion about the effects of three nonlinear coefficients on switching and transmission characteristics. They are group velocity mismatch, dispersive properties and difference effective mode field area. It shows that the nonlinear coefficients have different effects on the switching characteristics, coupler threshold power and the efficiency of energy transmission. In practice, the suitable coefficients need to be chosen according to different needs.Then, the soliton pulses propagation and switching in three-core nonlinear fiber couplers are investigated, using the split-step Fourier method(SSFM). The effects of the normal dispersion and anomalous dispersion and the effects of the nonlinear coefficient on switching and transmission characteristics are mainly highlighted. The research shows that couplers can get good switching characteristics in the anomalous dispersion region. It is proved that the threshold power decreases significantly and the switching efficiency increases when the value of three cores’ nonlinear coefficients increase at the same time.Finally, the all-optical logic gates in both twin-core and three-core nonlinear fiber couplers are stimulated. The research shows that twin-core coupler can supply AND and XOR gates with different input states, while three-core coupler can supply AND, NAND and XOR gates with different input states. Besides, three-core coupler can supply AND with two different states.