The Key Technologies Of High-speed Optical Fiber Communication System Based On Mode Division Multiplexing

The main medium of current tansmission system single mode fiber (SMF) may reachthe foreseen capacity crunch due to its inherent nonlinear effects. Therefore, it is vitalimportant to explore a suitable optical transport technique to resolve the bandwidth limit ofSMF. The mode division multiplexing (MDM) based on few mode fiber (FMF) is revivedunder this background. The limited and stable modes are used as independent signalchannels for MDM transmission, which can exponentially increase the system capacity andspectral efficiency with negligible performance impairments.The thesis starts from the basic principle, describes the basic structure and keytechniques of MDM. The main research achievements include the design and optimization ofFMF, mode converter, mode multiplexer/demultiplexer (MMUX/DeMMUX). Based on theanalysis of the mode characteristics of the FMF, the FMF is designed and fabricated, whichcan support four modes transmission with large effective areas for each mode. The measuredloss of fundamental mode is0.23dB/km at1550nm. Thus, the FMF is proved to support theapplication of MDM system effectively.After analyzing the working mechanisms and characteristics of the existingMMUXs/DeMMUXs, mode converters based on untilted/tilted fiber grating as modeconverters are designed and experimentally demonstrated which are used to convertfundamental mode to LP11and LP02mode successfully. FMF couplers are designed asMMUXs/DeMMUXs in order to realize LP01, LP11and LP02mode multiplexing/demultiplexing. It is found that the proposed MMUX/DeMUX based on FMF haveadvantages of high mode conversion ratio, low mode crosstalk, easy fabrication andmaintenance, and compact size.