Analysis of a novel four-mode micro-structured fiber with low-level crosstalk and high mode differential group delay

Abstract

In this paper, a novel four-mode micro-structured fiber with low-level crosstalk and high mode differential group delay is proposed to solve the large transmission capacity and low crosstalk problems in the mode division multiplexing system. Electromagnetic field distribution, crosstalk, mode differential group delay and dispersion of the fiber are studied by using the full-vector finite element method. To determine the particular parameters of the micro-structured fiber, the performances of the inter-core crosstalk and mode differential group delay (MDGD) are considered comprehensively under different conditions. Simulation results show that this fiber can support four-mode transmission with 19 cores over the whole C+L wavelength band when the cladding diameter is 125 μm. The inter-core crosstalks of LP01 mode, LP11 mode, LP21 mode and LP02 mode are -131.01, -96.36, -63.32, -49.96 dB respectively and the mode differential group delays are high as all of them are more than 160 ps/m. Therefore, compared with the previous work, this fiber has the lower inter-core crosstalk and larger MDGD. Owing to the large index difference between core and cladding, the n_eff differences between the linearly polarized modes are all larger than 10-3across the whole operating wavelength band, which is beneficial to low inter-mode corsstalk. Furthermore, the fabrication of this fiber is simple due to its preforming only need stacking technique to adjust the hexagonal structure geometry size without complex modified chemical vapor deposition process involved. The designed fiber can be used in short-distance and large-capacity transmission system, and it has potential applications in making the corresponding high power devices.