A Novel2×4Flexgrid Wavelength Selective Switch Based On Liquid Crystal Technology

With the rapid growth of communication services,Automaticallyswitched opticalnetwork get great development and step into practical stage. Automatically switchedoptical network enables operators to achieve dynamic wavelength assignment remotely,which can improve work efficiency and greatly reduce construction costs and operatingcosts of the network. Reconfigurable optical add/drop multiplexer (ROADM),which basedon1×N Wavelength selective switch (WSS) surporting any wavelength switch to any portattenuating and blocking, is the core modules of Automatically switched optical network.Firstly, this paper introduces the development and research status of ROADM, andhighlights the wavelengthselective switch based reconfigurableoptical add-dropmultiplexer technology. Then the current wavelength selective switchtechnical solutionsare described and compared, in which liquid crystal (LC) technology and liquid crystal onsilicon (LCoS) technology are considered more suitable for future100Gbit/s,400Gbit/sultra high-speed optical transmission systemsbecause of surporting flexible bandwidthfunction.Then, this paper presents a2×4flexgrid wavelength selective switch design basedonLC technology. The principle of the optical system design is to add polarization splitterand combinerin a conventional1×N wavelength selective switch, realized2×Nwavelength selective switch designthrough polarization multiplexing. Then the liquidcrystal attenuation control, flexible bandwidth control, polarization mode dispersion andworking bandwidth are analyzed in detail.Finally, a wavelength selective switchprototype is completedaccording to thedesign.Some key technical indicators, including port isolation, insertion loss, bandwidth,center wavelength, response timewere tested and analyzed.