Double-trench assisted thirteen-core five-mode fibers with low crosstalk and low non-linearity

Information technology has an increasingly strong demand for high-speed and large-capacity optical fiber networks. Space division multiplex(SDM) is a new generation of optical fiber communication technology which can be several times in communication capacity higher than the wavelength division multiplexing systems. In this paper, we present a kind of 13-core 5-mode fiber with double trench structure to meet the demand for high-speed and large-capacity information transmission in the future. In order to solve the crosstalk problem in SDM, a double-trench structure is adopted to better limit the light energy in the fiber core, thus reducing the crosstalk between cores and modes. The crosstalk and transmission characteristics of multi-core fiber are calculated and analyzed by the full vector finite element method and coupled power theory. After the optimization of structural parameters, the fiber can stably transmit LP01, LP11, LP21, LP02 and LP31 in the band of 1.3-1.7 mu m; when the signal is transmitted at the 1.55 mu m for 60 km, the inter-core crosstalks corresponding to the adjacent fiber cores in the above five modes are -122.37 dB, -114.76 dB, -106.28 dB, -100.68 dB and -92.813 dB, respectively; the effective refractive index difference between adjacent modes is greater than 1.026 x 10(-3); inter-core and inter-mode crosstalk can be effectively suppressed. The corresponding non-linear coefficients of the 5-modes are 0.74 W-1.km(-1), 0.82 W-1.km(-1), 0.88 W-1.km(-1), 1.26 W-1.km(-1), 0.93 W-1.km(-1), which can maintain low non-linear transmission. The structure of fiber is simple and compact, and the preform can be fabricated by vapor deposition method and stack method, then the 13-core five-mode fiber with low crosstalk and low nonlinear can be further drawn, which can be used in a long distance high-speed and large-capacity fiber transmission system.