Research On Ultra High Speed And Large Capacity Optical Fiber Transmission And Its Mode Division Multiplexer

In the past decades,the capacity of optical fiber communication system has increased dramatically with the increasing demand.But even so,because of the explosive growth of the Internet and broadband wireless services,it still can not meet the demanding of network.In order to break through the limitation of capacity,researchers have used time,wavelength,polarization,orbital angular momentum and other multiplexing methods.In order to further improve the transmission capacity of single fiber,researchers began to study space division multiplexing,including core multiplexing and mode multiplexing.Space division multiplexing has become a research hotspot of optical communication.Major companies and universities around the world,including Nokia Bell Labs,NTT company,University College London,University of Central Florida and other units,have relevant research on multi-core,few mode long-distance transmission,reducing mode cross-talk,increasing spectral efficiency of few mode,and multi-core fan in and fan out device.But there are still a series of problems to be solved,including the design and manufacture of mode multiplexing devices,the research of signal loading and demodulation in the system,and the crosstalk in the mode transmission system.In this paper,a series of in-depth theoretical and experimental researches have been carried out on the key problems of the MDM optical fiber communication system in the aspects of the MDM devices and system applications.The self-homodyne detection scheme,the balanced detection scheme of pilot supported direct detection system,the mode division multiplexing and wavelength conversion based on the high-order modulation format of silicon-based waveguide in the on-chip optical interconnection system,and the broadband plasma mode division multiplexer are explored.The main innovations are as follows:First of all,to solve the problem of high complexity caused by intradyne detection in optical communication transmission system,self-homodyne coherent detection based on few-mode fiber is proposed in this paper.We realize the conversion of the LP₀₁ mode to the high-order mode LP₁₁ through the spatial phase board,and transmit the pilot tone in LP₀₁mode and the PDM-CO-OFDM signal in LP₁₁ mode,the SHD-FMF transmission system with 16-QAM data transmission rate of 156Gb/s and 64-QAM data transmission rate of234Gb/s is realized in the experiment.(Please refer to Ying Qiu,et al.Technical Digest of ICCC'2016)Then,because of the disadvantages of high complexity and high cost of coherent detection method in optical fiber communication system,this paper adopts the direct detection technology of high-order modulation format transmission supported by pilot,which has simple structure and low cost.However,the direct detection technology has the problem that SSBI(interference between signal and signal)affects the system performance.To solve this problem,this paper proposes a balanced detection scheme of few-mode optical fiber,designs and makes a mode selective optical fiber mode demultiplexer,which realizes the balanced detection of 100Gb/s few-mode optical OFDM transmission and successfully removes SSBI.(Please refer to Ying Qiu,et al.Technical Digest of ECOC'2017 and Ying Qiu,et al.IEEE Photonics Journal,2018,10(5):7105010)Next,in order to solve the problem of mode conversion and wavelength conflict of multimode high-order modulation scheme in on-chip optical interconnection system by using silicon-based waveguide and its high nonlinearity,a SOI TE₀&TE₁ mode multiplexer and demultiplexer are designed and fabricated.In the on-chip optical interconnection system,using the optical signal modulation of OFDM-4QAM,the wavelength conversion of mode selection is realized experimentally,and the optical OFDM-4QAM signal transmission of 102.6Gb/s is realized at the same time.(Please refer to Ying Qiu,et al.Optics Express,2017,25(4):4493-4499)Finally,to achieve the high bandwidth application of the mode division multiplexer,the TM₀&TM₁ mode division multiplexer based on dielectric loaded surface plasmon waveguide is studied theoretically.Two structures of TM₀&TM₁ mode division multiplexer are designed.The coupling length is 6?7?m,and the bandwidth is 400nm.The devices have the advantages of compact structure and wide bandwidth.(Please refer to Ying Qiu,et al.Current Applied Physics,2020,20:244-248)...