Research On The Design And Characteristics Of Multi-core And Few-mode Fibers

With the rapid development of optical network transmission technology,people's demand for optical fiber transmission capacity is increasing day by day.As the capacity of traditional single-mode optical fiber is gradually approaching the limit of Shannon,the development is bottlenecked,and the capacity crisis is increasingly highlighted.Although it is possible to modulate and multiplex the transmission optical signal from the dimensions of time,wavelength,frequency,and amplitude to increase its transmission capacity as much as possible,substantive progress cannot be made due to the limitations of nonlinear noise and amplifier bandwidth.Therefore,in order to fundamentally solve the capacity problem,the space division multiplexing technology of optical signals has ushered in a new development opportunity,which can achieve spectral efficiency by expanding the use of the two spatial dimensions of the number of fiber cores and the number of modes.And the increase in capacity.Therefore,research on the key technologies of space division multiplexing systems is of great significance and is expected to bring new breakthroughs in optical communication transmission.Therefore,this paper mainly focuses on the structural design and performance simulation of multi-core and few-mode in the space division multiplexing system,and analyzes the structural parameters and performance indicators of the optical fiber:a heterogeneous and multiple auxiliary structure of nineteen-core three is proposed.Mode fiber design;simulation study the performance of 4-LP low differential mode delay(DMD)few-mode fiber assisted by dense air hole group;design a built-in grooved multilayer elliptical core weakly coupled few mode The optical fiber was analyzed.The main research work of this paper is as follows:(1)Based on the performance parameters of the optical fiber structure and basic theoretical analysis,various loss factors in the multi-core and few-mode optical fiber channel are simulated.On the basis of the current multi-core optical fiber design research,a 19-core three-mode optical fiber structure model is built based on the Finite Element Method.The influence of the groove structure and the low-refractive-index hole structure on the performance of the optical fiber is simulated,and the structural parameters of the nineteen-core optical fiber are determined.The crosstalk between cores is below-50dB/100km,and the Relative Core Multiplicity Factor(RCMF)reaches about 30.2.On the basis of this optical fiber,a unified design scheme for a variety of multi-core optical fibers has been further proposed.(2)Designed 4-LP low-differential mode delay(DMD)few-mode fiber assisted by dense air hole group and performed performance simulation analysis.This solution uses three identical dense air hole groups as the auxiliary structure,each dense air hole group is composed of two air holes with different pore sizes,and the core refractive index distribution adopts a gradual distribution.The few-mode fiber is composed of 4 polarization modes in total,and can support the multiplexing of 12 mode channels.In the entire C+L band in all patterns of differential mode delay|DMD| less than 40 ps/km.The few-mode fiber designed in this scheme can effectively increase the transmission distance of the optical signal and reduce the complexity and system power consumption of the multiple-input multiple-output(MIMO)algorithm used in the receiving end system.(3)A multilayer elliptical core weakly coupled few-mode fiber structure with built-in grooves is designed,and performance simulation analysis is performed.The main design principle is:a double-layer elliptical core is used,which is composed of an inner elliptical core and an outer elliptical ring core.A low-refractive-index trench structure is built between the two cores.Two air hole structures are added on both sides of the elliptical core to break the symmetry of the fiber and introduce the birefringence effect.After simulation,the effective refractive index difference between each mode(including the polarization mode between the mode groups)is ?neff>1.6x1 0E-4,which can support the transmission of 16 spatial modes in total.