All-optical Logic Gate Based On Fiber Nonlinear Effects

Just the optical fiber transmission network system come to application soon, people realized that the bottleneck of electrical relay, with the development of technology, fiber optical transmission network from a traditional optical-electro-optical relay upgrade to all-optical amplification relay, erbium-doped fiber amplifier become to the most common amplify device. Moreover, in pursuit of faster communication, people set their sights on all-optical switching, optical switching have the picosecond, femtosecond response level, much higher than the traditional network power switch's speed-milliseconds. So looking forward to the future ultra-high speed fiber optic systems, optical information processing and photonic computer system, all-optical switching plays a very important role, and all-optical logic devices will also be essential to the basic unit.This paper first summarizes the latest research results in all-optical logic gates area, and introduces the principles of various all optical logic gates, construction methods and their advantages and disadvantages, particularly, the research-based on semiconductor optical amplifier's all-optical logic gates. Although based on semiconductor optical amplifier all-optical logic gates have the advantages in providing high linearity, ease of integration, etc., but the speed of the nonlinear response of the order of only nanoseconds, far below the optical nonlinearity, femtosecond.Subsequent chapters focus on nonlinear optical fiber-based all-optical logic gates. The second chapter introduces the various nonlinear in optical fibers, such as:self-phase modulation, cross-phase modulation, stimulated Raman scattering, four-wave mixing and so on. Then, the concepts and theories about research nonlinear all-optical logic gates established. And in third chapter, the essay briefly introduces two all-optical logic gates: cross-phase modulation-based and erbium-doped fiber amplifier-based all-optical logic gates.Then, this study focused on the chapter four and five, through the optical fiber coupler coupled mode theory combined with the computer's numerical calculation, and software MATLAB simulation, the study of ordinary optical fiber couplers and the effection of higher-order optical nonlinear are provided. After extended and analogy, the performance about the active fiber optic coupler, and a novel active fiber coupler all-optical logic OR gate have been researched, then the XOR gate simulated successfully, the active fiber coupler's two output ports can be executed OR and XOR. Such logic gate is not only easy to integrate with the traditional optical interface; its degree of sharpness of the switch is much higher than ordinary light switch. But the structure of such logic gates to achieve the required length of optical fiber 175 meters, is not conducive to the actual use, this phenomenon mainly due to the nonlinear optical fiber itself cannot provide a high coefficient.Finally, it summarizes the results of research and gives the future development of all-optical logic gates'trend. Due to photonic crystal fiber's high nonlinear coefficient, therefore, it may become all-optical logic gates'main device.