Design On Electro-optical Tunable ROADM Based On Lithium Niobate Waveguide

Reconfigurable optical add/drop multiplexer (ROADM), which is able todistribute channels dynamically, is an indispensable key node equipment in theprocess that Wavelength Division Multiplexing (WDM) system evolves into AllOptical Network, and is also the significant foundation in realizing the intelligentoptical network. It can download certain wavelength from the multi-wavelength linesignal to local and upload certain wavelength from local to line signal. Moreover, it iscapable of tuning the add/drop wavelength dynamically, thereby, it realizes thedynamically reconfigurable optical network and accelerate the process oftransparentizing and intelligentizing the optical network.The actual technologies of ROADM are mostly based on separate opticalcomponents, which induce high cost, low reliability and unsuitable for integration.Besides, for the tuning method limited, those ROADMs'response speed is somewhatlow comparing to that of superhigh speed network. In order to meet the needs ofROADM for optical network, this thesis propose a novel electro-optical tunableROADM. With the structure of titanium diffused lithium niobate waveguide, itsoptical part consists of a polarization conversion section (PCS) and two polarizationbeam splitters (PBS). The PCS has tens of polarization conversion unit (PCU) andwavelength tuning unit (WTU) distributing alternately along waveguides. The deviceuses electro-optical grating to convert the polarization and electro-optic effect to tunethe wavelength.This thesis starts with the fundamental principles of waveguide optics, optronics,mode-coupled and some other theories and then deduces how the device's parametersaffect its performances. Furthermore, it calculates the geometry and physicalparameters of the device and designs the manufacture parameters of the titaniumdiffused lithium niobate waveguide used in the device, the parameters of waveguidesin PBS and PCS and the voltages applied by the electrodes in PCU and WTU. In theend, the thesis propose several PCU voltage distributions to fulfill the pass-bandwidthand sidelobe suppression demands and it gives several schemes as standby whichmatch low reconfiguration level conditions.Theoretic analysis and emulational research shows that the ROADM designed inthe thesis performs high integration level, rapid response speed, narrow pass-band and low sidelobe. Furthermore, it can modulate the bandwidth without changing thedevice structure to fulfill the requirement for Dense Wavelength DivisionMultiplexing systems with different channel spacing or download neighboringchannels synchronously.