Theoretical And Experimental Research Of Photonic Lantern Devices In Optical Communication Systems

Because single-mode optical fiber communication system capacity has become increasingly close to its nonlinear Shannon limit.In recent years,mode division multiplexing technology using spatial dimension is considered as effective technical means which be able to break through the capacity bottlenecks of traditional single-mode optical fiber communication system transmission.One of the most important parts of the mode division multiplexing system is multiplexing/de-multiplexer.Based on the mode theory and the adiabatic criterion in fiber,we have studied several methods of mode multiplexing and de-multiplexing based on photonic lanterns in mode division multiplexing system,and proposed a new design method of degenerate mode selection photonic lanterns based on elliptical-core few mode fiber.the principle of several photonic lanterns and proposes a new elliptical weakly-coupled photonic lantern device.The main attributions and innovations of this dissertation are as the following four aspects:1.This paper analyzes the basic principles of the few mode fiber and the photonic lantern,and expounds the numerical calculation methods of the photonic lantern.According to the different functions of the photonic lantern,we study the traditional non-selective photonic lanterns and the mode-selective photonic lanterns respectively.2.This paper studies the mode-selective photonic lantern based on circular-core few mode fiber,and designs and optimizes its basic structure and carries on the simulation analysis based on the beam propagation method and the finite element method.The simulation results show that the losses of LP01,LP11a and LP11b modes are 0.11 dB,0.13 dB,0.13 dB for photonic lantern supporting three modes,and the losses of LPO1,LP11a,LP11b,LP21a,LP21b,LP02 modes for photonic lantern supporting six modes are 0.023 dB,0.033 dB,0.117 dB,0.157 dB,0.310 dB,0.322 dB,respectively.3.According to the principle of adiabatic condition,we have fabricated a mode-selective photonic lantern supporting three modes,which can realize the selection function of LP01,LP11a and LP11b mode.The losses of LP01,LPl1a and LP11b mode are 0.5 dB,0.83 dB and 0.41 dB respectively.4.In order to solve the problem of mode mismatch between elliptical-core few mode fiber and existing mode multiplexing/de-multiplexer in the weakly coupled mode division multiplexing system which is transmitted by elliptical-core few mode fiber,we propose and simulate a mode-selective photonic lantern for the first time,of which degenerated modes are weakly coupling,which is based on elliptical-core few mode fiber.And the simulation results show that the elliptical-core mode-selective photonic lantern proposed in this paper can realize the selection functions of all the modes.The loss of LP01,LP11a and LP11b mode is 0.05 dB,0.04 dB and 0.05 dB respectively.The mode crosstalk is below-20.8 dB for all modes.For the mode-selective photonic lantern supporting six modes employing either six step index or six graded index fibers,the all loss is less than 0.35 dB and the crosstalk of mode is less than-20 dB.