Study Of Polymer-Integrated-Waveguide-Based Demultiplexer

With the rapid development of optical communication technology,the user demand for wide bandwidth is also rising.As a result of ADSL(Asymmetric Digital Subscriber Line) access network bandwidth has gradually become the bottleneck of application,FTTH(Fiber To The Home) becomes a next-generation access network for its wide bandwidth.FTTH meets high-bandwidth demand on data,voice,CATV and other integrated services.However,a widely use of FTTH requires further reduction of cost.According to ITU-T suggestions,there are three wavelengths in FTTH access networks,including 1490nm and 1550nm as the downlink messaging windows,carrying the voice/data signal and CATV signal respectively,and 1310nm as the uplink information transmission window,carrying voice/data signal.Cost can be greatly reduced if these three wavelengths transmit in one fiber.In this way,low-cost,high-performance triplexer becomes one of the key factors.In this dissertation,relevant optical and structural parameters of triplexer are discussed, according to the optical properties of novel liquid polymer material PSQ,including refractive index,dispersion and birefringence.The principle of involved planar-lightwave-circuit-based triplexer for separating three wavelengths is analyzed.The triplexer consists of two kinds of waveguide planar structure. They are asymmetric Y junction and directional coupler.The principle of asymmetric Y junction for separating 1310nm from the other two wavelengths,1490nm and 1550nm,is discussed.It is explained that the involved triplexer has nothing to do with the polarization besides owning a wide bandwith.The coupled-mode theory is used to investigate principle of directional coupler for separating 1490nm and 1550nm.PSQ is used as the optical waveguide core and cladding material.The involved planar-lightwave-circuit-based triplexer is designed under single mode condition.First of all, the refractive index of waveguide and cross-section size is discussed and then determined. Secondly,the effect of change in branch angle and length on filtering property of Y junction is investigated,and the structure is optimized.Next,the impact of change in coupling distance on filtering property of directional coupler is discussed.A method of determination of coupling length is explained.Finally,PSQ material dispersion and birefringence are considered.A grating coupler on optical waveguide is designed using PPESK as the waveguide core material.The principle of the coupler is analyzed.It is studied that the impact of grating depth and duty cycle on coupling efficiency.