Electro-Optic Mode Switch Based On Lithium-Niobate Mach-Zehnder Interferometer

With the incremental popularity of the personal mobile and broadband internet services, the users demand for an optical transmission system with larger transmission capacity and more flexible performances. However with the applications of dense-wavelength-division-multiplexing, orthogonal-frequency-division-multiplexing and many other typical technologies, the transmission capacity of the single-mode-fiber-based fiber transmission system is rapidly reaching its theoretical limitation. Space-division-multiplexing, which can exploit the space dimension, is a promising technology to further increase the transmission capacity so as to meet the rapid growth demand of the internet traffic. Mode-divison-multiplexing based on the few-mode fiber is an important candidate to realize long-distant transmission system with extremely large transmission capacity. Mode converter or mode multiplexer plays a critical role in the mode-divison-multiplexing system and hence arouse vast amount of interets. In recent years, various kinds of mode converters or multiplexers have been reported.Mode converter or multiplexer of high quality should be capable of low insertion loss, low crosstalk, wide operating bandwidth and relative ease of fabrication. In the propesctive optical network, dynamic rounting and reconfiguration are essential. Therefore devices with flexible performances are more suitable for future application. The research object of this dissertation is aimed at realizing reconfigurable or tunable mode converter and multiplexer, which can be applied in the prospective mode-division-multiplexing system.By now, electro-optic mode converter based on lithium-niobate Mach-Zehnder interferometer and mode multiplexer based on the lithium-niobate asymmetrical Y-junction have been already analyzed and experimentally demonstrated. The mode converter based on the lithium-niobate Mach-Zehnder interferometer has the advantage of reconfiguration, wide operating width, low driving voltage and fast-switching speed. By fabricating and characterizing the devices, the operating properties of the device have been already demonstrated. The experimental results agree well with stimulation results.There are many useful applications for the proposed devices in the prospective reconfigurable mode-divison-multiplexing system.