Coupling Filter Based On Axisymmetric Twin-core Fiber

The researchers proposed a coupling filter based on an axisymmetric twin-core fiber. The filter combines the cores of two ordinary single-mode fibers with a section of the same axisymmetric non-coaxial twin-core with two cores of length L. The centers of the optical fibers are fused together, and then the two single-mode optical fibers are connected to the broadband light source and the spectrum analyzer respectively, and the comb spectrum of the filter can be observed through the spectrum analyzer. The filter based on the dual-core fiber coupling type has a simple structure and is easy to manufacture. However, due to the mismatch between the mode fields of the axisymmetric dual-core fiber and the single-mode fiber, the coupling efficiency and insertion loss of the filter will be affected.