Special optical fiber with special refractive index distribution

Dual-core fiber is a special fiber with a special refractive index distribution. It breaks through the refractive index distribution structure of conventional optical fibers. Two parallel cores are arranged in the same fiber, which can be used as optical transmission medium and New optical devices can be constructed. In the early 1960s, some scholars studied the energy coupling of light between two parallel waveguides. In 1980, the experimental verification of dual-core fiber made a major breakthrough in coupled mode theory. In 1981, researchers used dual-core optical fiber to measure the coupling characteristics of curved waveguides and the relationship between the coupling coefficient and the bending radius to design a fiber-type optical direction coupling switch. In the late 1980s, researchers used the dual-core fiber's selectivity to wavelength and polarization and its spectral characteristics to initially apply the dual-core fiber to optical sensing devices, including the measurement of temperature, stress, and displacement. Subsequently, the nonlinear effects of dual-core fibers have also been studied for the realization of passive mode locking devices and ultra-fast all-optical switches. Fiber optic devices based on dual-core fibers have the advantages of easy and precise control of device size, small mechanical stress in the coupling zone, more compactness and stability, and less susceptibility to external influences. They have been widely used in many fields such as optical sensing and optical communications. Reflected in fiber filters, optical interferometers, optical connectors, fiber amplifiers, optical add/drop multiplexers, fiber switches, optical tweezers, and fiber sensors. Therefore, the study of dual-core optical fiber has important theoretical and practical significance. As the research deepens, it will bring new breakthroughs to optical fiber communication and optical fiber sensing.