The Research On Characteristics Of Reconfigurable Optical Add/Drop Multiplexer Based On Photonic Crystals

As the rush development of optical communication technology and the continuous emergence of new businesses, the optical network has witnessed tremendous evolution. The next generation WDM all-optical network with functions of all-optical switching, all-optical routing and intelligent wavelength assignment is under developing. As the key equipment of WDM all-optical network, the reconfigurable optical add/drop multiplexer (ROADM) is becoming the research focus of the field of optical communication. With the Characteristics of small size, easy to integrate and capable to control light, the photonic crystals has been widely used to design optical filters, modulators, switches and other functional devices in optical communication systems. The photonic crystals provides a new approach to design the compact integrated ROADM. The study of ROADM based on photonic crystals will play an important role in the development of WDM all-optical networks.The paper firstly investigated different defect states in 2D photonic crystal and the coupling theory between them with PWE and FDTD method. On the basis of photonic crystals waveguide coupling theory, a 2×2 optical switch based on Phenylacetylene liquid crystal is designed. The switching performance of the 2×2 optical switch in both the cross and bar states has been analyzed. The results show that optical switch has low insertion loss and high channel isolation, and the switching time is in ms magnitude. Then using the 2×2 optical switch and a simple three-port photonic crystals waveguide coupling filter, a photonic crystals switching ROADM is proposed. With the 2×2 optical switch, the wavelength of optical channels which is added/dropped by ROADM can be adjusted. The switching ROADM is compact, and can be cascaded into a multi-channel ROADM. However, the switching ROADM is not flexible enough, because the reconfiguration of wavelength is controlled by the optical switch. In order to improve the flexibility of the wavelength reconstruction, a new photonic crystal tuning ROADM is proposed, and its tuning performance is analyzed. The structure of the tuning ROADM is improved, by changing the radius of the posts located between point defect micro-cavity and line defect waveguide. Simulation results show that the wavelength of optical channels which is added/dropped by ROADM can be reconfigured from 1538 nm to 1570 nm , the insertion loss and wavelength channel crosstalk is low and the reconfigure time is in ms magnitude. Finally, the application of the tuning ROADM in all-optical network is studied.