Vector coupled-mode calculation of guided vector modes on an equilateral three-core optical fiber

The guided vector modes propagating on an equilateral three-core optical fiber in which the component cores are identical, single-mode, and arrayed in an equilateral triangle are determined using the coupled-mode approach. It is shown that in the case of weakly guiding fibers, the polarization patterns of the six vector array modes can be correctly obtained if the vectorial-form coupled-mode theory is applied and the coupling among the six HE/sub 11/ modes of the individual cores is considered. However, it is found that the accuracy of the coupled-mode analysis decreases as the fibers become more strongly guiding, and the predicted field patterns are distorted.<>