Research On The Supermodes Of Multi-core Fiber And Its Applications In Sensing

Due to the special structure of the multi-core fiber,it has important applications in the fields of space division multiplexing and fiber sensing.This paper analyzes the mode characteristics of multi-core fiber with different structural parameters,and focuses on the application of weakly coupled multi-core fiber in fiber sensing.On the one hand,the super-modeling and power coupling characteristics of multi-core fiber are systematically analyzed.On the other hand,a new multi-core fiber sensing structure is proposed,and its strain sensing and curvature are studied in detail through simulation and experiment.Sensing and other applications.The main research contents and innovations of this paper include:(1)Using the coupled mode theory,the inter-core coupling characteristics of strongly coupled multi-core fibers are analyzed.The influence of the structural parameters of the strongly coupled multi-core fiber on the super-mode field distribution is studied by the beam propagation method.The influence of the structural parameters of the strongly coupled multi-core fiber on the power coupling characteristics is analyzed.(2)The principle of mode interference of strongly coupled multi-core fiber is simulated by beam propagation method.The influence of structural parameters of strongly coupled multi-core fiber on mode interference process is analyzed.An interferometric estimation method for the core spacing of strongly coupled multi-core fibers is proposed.According to the interference spectrum of the strongly coupled multi-core fiber and its core spacing,the core spacing can be estimated by observing the interference spectrum.(3)A novel sensing structure based on weakly coupled multi-core fiber is proposed.The fiber structure consists of a weakly coupled multi-core fiber and two single-mode fibers.The multi-core fiber is eccentrically fused to the input terminal.Molding fiber to produce a stronger cladding mode.The other end of the multi-core fiber is fused to the single-mode fiber at the output end,and the taper is tapped at the fusion point.The introduction of the tapered structure is beneficial to increase the power ratio between the core mode and the cladding mode participating in the interference,which can improve the extinction ratio of the interference spectrum.Through simulation and experiment,the spectral characteristics of the fiber-optic sensing structure are studied in detail with different structural parameters,and the fiber structure is successfully applied to the measurement of physical quantities such as curvature and strain.An improvement in the interference effect of the structure after introducing more taper into the structure is also analyzed.