Design And Performance Analysis Of Multi-core And Low-mode Fiber Based On Various Auxiliary Structures

Since Dr.Kao proposed the basic theory of optical fiber communication,the optical fiber communication technology surrounding the enhancement of optical fiber communication capacity has been a research hotspot at home and abroad.In recent years,with the rise of 5G,big data,cloud computing,cloud storage and other new technologies,and the accelerating digitization process,higher demand has been put forward for the optical fiber communication capacity as the physical layer carrying the business.At present,the transmission capacity of single-mode fiber has reached the limit of Shannon's theory,while the space division multiplexing technology has broken through the Shannon limit of single-mode fiber in the traditional sense by means of multi-core multiplexing or orthogonal mode multiplexing,and can achieve a great improvement in the transmission capacity of single fiber.This paper mainly studies the structure design of multi-core and low-mode fiber in space division multiplexing system and analyzes the performance parameters of multi-core and low-mode fiber theoretically.In this paper,we propose a design method of multi-core and low-mode fiber based on heterogeneous double-cladding groove auxiliary structure.In addition,we design a 7-core and 10-mode fiber and a new double-coupled ring assisted 6-LP low-mode fiber structure.Enhanced fiber transmission capacity.The main research work is as follows:1.A design method for multi-core and low-mode fiber with heterostructure assisted by double-cladding grooves is proposed.Firstly,the theoretical model of heterostructured double-cladding grooving fiber was established by using the finite element method.Then,the effects of structural parameters on the performance of heterogeneous double-cladding fiber,including the effects of inner cladding height and width on the effective mode field area(Aeff),bending loss(BL),differential mode group delay(DMD)and mode dispersion,are simulated and analyzed.The results show that,compared with the optical properties of the traditional step fiber,the proposed scheme can increase the effective mode field area,reduce the nonlinear effect,and has significant advantages in bending resistance and dispersion reduction.2.A triisomeric 7-core 10-mode fiber with a cladding diameter of 170?m was designed based on the heterogenous double-cladding groove auxiliary structure,and the influencing factors of intercore crosstalk(XT)and bending loss were simulated and analyzed.The simulation results show that the designed fiber maintains a low crosstalk below-60 dB/km,a large effective mode area of more than 140 ?m2,a low mode dispersion of less than 18.9 ps/(km*nm)and a relative multiplicity factor of 49 in the C+L band.3.In order to reduce the problem of inter-mode crosstalk in the low-mode fiber,a new double-coupled ring assisted low-mode fiber structure design is proposed.Firstly,the fiber structure is modeled with COMSOL and the main influencing factors of coupling between modes are analyzed.Then,the five parameters of the double-coupled ring are simulated and analyzed.The results show that Aeff index difference between LP21 mode and LP02 mode is the closest in the 6-LP low-mode fiber,and the difference is the main factor affecting the cross-talk.The minimum mode refractive index difference between LP21 mode and LP02 mode is 1.5×10-3,which is 1.88 times of the minimum refractive index difference of the traditional step structure under the same conditions.