The Structure Of The Two Cores Inside And Outside The Twin-core Optical Cable

The dual-core fiber has two cores in the cladding, which is a special fiber. Starting from the physical structure of the optical waveguide, dual-core fibers are mainly divided into coaxial dual-core fibers and non-coaxial dual-core fibers. In recent years, photonic crystal twin-core fibers, ribbon twin-core fibers and twin-core fibers have also appeared.

Coaxial twin-core fiber

Coaxial twin-core fiber, also called double-clad fiber or double-ring core fiber, means that the two cores in the cladding are on the same axis with the center of the cladding as the axis, showing a structure of two cores inside and outside. Coaxial twin-core fibers are often used to make high-power fiber lasers.

Non-coaxial twin-core fiber

Non-coaxial twin-core fiber is a fiber with two independent cores in the cladding. According to the position distribution of the two cores, the non-coaxial twin-core fiber can be divided into axisymmetric (relative to the center of the fiber cladding) non-coaxial twin-core fiber and an axis-shifted non-coaxial twin-core fiber. Axisymmetric non-coaxial symmetric twin-core fiber with two cores symmetrical to the center of the waveguide. The two cores of the axis-shifted non-coaxial twin-core fiber are still parallel cores, but the symmetrical axis of the two cores is offset on one side of the fiber. Typically, for example, one of the cores can be located exactly on the center axis of the entire dual-core optical fiber. In addition, if the refractive index and shape of the two cores of a dual-core fiber are the same, it can be called a matched dual-core fiber. If the refractive index and shape of the two cores are not the same, it can be called a mismatched dual-core fiber.