Design And Fabrication Of WDM Component Based On Off-axis Holographic Lens

Wavelength division multiplexing (WDM) technology is an effective way to increase information-carrying capacity. And wavelength division multiplexers and demultiplexers (WDMs) are key devices in WDM technology, the performance of which has a decisive influence on the quality of transmission in WDM system. WDMs based on off-axis holographic lens (OHL) are new devices having great development potential, which are proposed by the research group led by Professor Liu Shou of Xiamen University. The devices not only have the common advantage of WDMs based on diffraction gratings, viz. being scalable, but also have the predominance of having simple structure and few auxiliary components. Furthermore, the fabrication method and process of the main component, viz. WDM component based on OHL, are relatively simple, and the component is suitable for mass production by replication technique. The progress made by Liu Shou group showed that the new devices have application potential in course WDM. But there still exist the problems of big wavelength spacing, small isolation and high insertion loss. The dissertation focuses on the theoretical design and fabrication technique of WDM component based on OHL, aiming at decreasing the wavelength spacing of the new devices to mine their application potential in dense WDM, and at the same time improving the main performance parameters of the devices to meet practical requirements. Firstly, the basic working principle of the component was introduced, the basic requirements when designing the component and the main performance requirements for the component was summarized, and three samples of the component were disigned based on analyzing the main performance parameters of the component, taking the case for example in which the wavelength spacing between adjacent channels is . Then the three samples were fabricated according to the design parameters, performance of the three WDMs based on OHL composed of each sample was tested, and testing results of the three adjacent channels with the designed center wavelengthes of 5nm 1545nm 1550nm and 1555nm were given. The results demonstrate that the performance of the device composed of sample 2# (hereinafter referred to as device 2#) is relatively good and can meet practical requirements by and large, there only exists the problem of high insertion loss; and if the cladding diameters of receiving fibers are decreased by etching, sample 2# can comprise WDMs with wavelength spacing of 2.4nm. Matters needing attention when using sample 2#, methods to reduce the insertion loss of device 2# and the design scheme which may further decrease wavelength spacing of device 2# were discussed subsequently. Finally, the exploratory research about the fabrication technique and process of mass-producing WDM component based on OHL using electroforming technique and hot-pressing technique was introduced. The main contributions and innovations presented in the dissertation are as follows:1. Two basic design requirements and three main performance requirements of WDM component based on OHL have been summarized systematically.2. The diffraction efficiency of WDM component based on OHL has been analyzed using coupled-wave theory, and the conditions in which the component can have high diffraction efficiency have been obtained.3. The range in which holographic aberration theory can be used has been obtained by analyzing the formation and influencing factors of monochromatic aberration; then the monochromatic aberration of WDM component based on OHL has been analyzed using the theory, and the conditions in which the component can have small monochromatic aberration have been obtained.4. The expression of resolving power of WDM component based on OHL has been obtained by analysis using scalar diffraction theory; and the minimum number of grating grooves irradiated by the input lightwave, which can make the component have sufficiently high resolving power, has been calculated according to experimental data.5. The WDM component based on OHL which can comprise WDMs with wavelength spacing of 2.4nm has been designed and fabricated, thereby it has been proved that WDMs based on OHL have application potential in dense WDM; and at the same time, isolation of the devices has been improved greatly and can basically meet the requirement of digital communication system.