Improve The Accuracy Of Variable Fiber Delay Line

In recent years, people's need to information has become more and more, which directly pushes the technology of optical fiber communication to develope fastly. The research on microwave signal transmissions by using optical fiber is more and more active. Having capacities of processing signal in frequency or time domain is one of very important characteristics of fiber, the optical fiber delay lines is a typical model. Because the optical fiber delay lines have many advantages comparing with the traditional electronic delay lines, certainly it will get extensive application in the future. Starting the research work right now seems to be very meaningful.Based on the principle of optical fiber delay line, several modules composed of delay lines are introduced compendiously, which provides the theoretical fundation to select modules in designing system of delay lines. In chapter 2, we introduce several optical delay lines and analyse their advantages and disadvantages. Several 3-bit variable optical fiber delay units are designed and analysed on the basis of the conditions of our laboratory.The subject of this thesis is for to improve the delay precision. For implementing the aim, the technology of impoving delay precision is researched from two sides in the following chapters. On one hand, the structure of delay unit is redesigned. In the case of the structure composed of three 2×2 optical switches, the relations between the status of optical switches and delay error are analysed by calculation and deduction, then a new delay unit composed of six 1×2 optical switches is designed and take place of the tranditional structure. On the other hand, a new technology using tunable laser as light source of delay system is proposed, which uses the characteristics of optical fiber material dispersion which means that the refraction index of optical fiber changes along with the difference of transmitting wavelength. At the same time, the period of optical signal storage in delay lines is also altered and the delay precision of optical fiber delay lines is improved. The theoretical delay in ideal circumstances, the initial delay and the amendentory delay after altering the wavelength of LD are simulated respectively. The simulation results indicate the mean error of time delay...