An efficient evaluation model of fusion splice with different transverse offset and angular misalignment for few mode fiber

In this paper, based on a scale-adapted set of Laguerre-Gaussian modes, a theoretical model has been presented for evaluating the coupling efficiency of modes and mode crosstalk between different spatial modes caused by transverse offset and angular misalignments. A proof-of-model demonstration is performed for three-mode fiber, and the results show that the coupling efficiency and mode crosstalk of various modes behaves differently in the presence of axial offset and the direction of the misalignment. And it is also demonstrated that the proposed scheme can be scalable to analyze the FMFs with a large number of modes. On the basis of this model, the tolerance of coupling efficiency to the fusion splice conditions with different FMF parameter is analyzed. The results show that the larger the FMF normalized frequency V, the smaller the tolerance of spatial mode coupling to the transverse offset value. With the increase of V value, the tolerance of self-coupling efficiency and mode crosstalk to angular misalignments changes regularly. Therefore, the transverse offset and angular misalignments of fusion splice with different FMF parameters need to be strictly controlled to achieve suitable mode coupling efficiency and mode crosstalk.