Study On Optical Coupling Theories For Nodes In Optical Networks

With development of optical communication technology, the demand for optical devices has become higher. The optical devices move toward smaller volume and larger scale integration, with the high speed of intergraded optical technology. Using intergraded optical devices, the volume of optical nodes is reduced, while the quality of optical nodes will be improved. The key to integration and packaging for optical devices is optical coupling technology. Optical coupling technology keeps space with optical devices.Both the high speed development of optical networks technology and the rapid increasing IP service need high performance of optical networks structure and good quality of optical nodes at the present stage. In order to enable IP burst service and increase bandwidth utilization rate, a new solution called light-trails network is proposed. Optical fiber element is primary in the optical nods of light-trails. With development of intergraded optical technology, some optical waveguide devices may be used in optical nodes of light-trails, such as waveguide grating coupler can be used as a optical coupler. The problem that the optical coupling between optical fiber and waveguide grating must be solved. In this thesis, wide waveguide grating and expand core fiber are proposed to make the devices packaging easy:based on the theory of coupling between Gaussian beam and waveguide grating, an expand core fiber is designed and analyzed using the method of matrix optics technologies and Gaussian beam theories. After the coupling loss is analyzed, the model of coupling for expand core fiber with waveguide grating is built. At last the structure tolerance of the expand core fiber is studied. And then the optical coupling efficiency imposed by the position of Gaussian beam on the grating is discussed. The results show that the position tolerance of the expand core fiber is much larger.Fiber to the home (FTTH) technology is the major solutions for broadband access networks. The triplexer is a core device, because lower cost and the better optical characteristics are most important. It is a hot issue about planar optical waveguide triplexer now, so the status of this device is introduced. A new planar optical waveguide triplexer consists of a multimode interference coupler and novel direction coupler is designed. Using extraneous self-imaging phenomenon of multimode interference coupler with weak-guiding condition, the length of the designed multimode interference coupler is shortened. Then, using optical waveguide coupling theory, a direction coupler is designed by coupling a bent waveguide with one output waveguide of multimode interference coupler. Based on the output power spectrum of triplexer, the bandwidth of the triplexer is up to ITU standard and the insert loss is much lower.