Fiber Optics Devices For Mode Division Multiplexing Transmission

In order to satisfy the severe requirement of fiber optical transmission,the capacity of traditional standard single mode fiber(SSMF)is fast approaching its theoretical limitation.Since the capacity crunch becomes a hot research topic around the world,mode division multiplexing(MDM)is believed as one of effective solutions to deal with the capacity crunch.The thesis is focused on the MDM enabled techniques including few-mode fiber(FMF)and fiber optical device,aiming to promote the MDM implementation.The main research outcomes of thesis are summarized as follows,(1)We present a comprehensive review of mode characteristics of FMF and operation principle of photonic lantern.Solid theoretical foundation is provided for the design and fabrication of FMF and photon lantern.(2)By using the Comsol Multiphysics software,we design and numerically investigate three types of specialty FMFs including panda-type FMF,elliptical-core FMF and panda-type elliptical-core FMF,in order to suppress both spatial and polarization degeneracy.In comparison with the traditional circular-core FMF,the panda-type FMF can break the degeneracy between both spatial and polarization modes.Although the elliptical-core structure is unable to mitigate the polarization mode coupling,it plays a role for the spacing enhancement of spatial modes.In particular,when the combination of the panda-type structure and the elliptical-core is used,the degeneracy of spatial modes and polarization modes arising in the FMF can be greatly suppressed,providing parallel transmission channels without the mode coupling.(3)By using Rsoft BPM software,we present the design of mode group selective photon lantern.With the objective of high mode group selectivity,high mode conversion efficiency and low insertion loss,the design of photonic lantern supporting 3 modes,6modes and 10 modes is demonstrated,respectively.The design strategy,optimization procedure and performance comparison are reported in details.Especially,considering the trade-off between high mode group selectivity and high mode numbers of photon lantern,we innovatively propose an elliptical-core structure together with a two-step tapering in order to achieve a ten-mode photon lantern with high mode selectivity.(4)By using Vytran GPX-3400 optical fiber processing platform,we successfully fabricate a three-mode photon lantern.Both high mode group selectivity and low insertion loss can be achieved,together with the quantitative package test.