Thermal diffusion coupling mechanism and its application of discrete waveguide

For discrete optical systems integrated into optical fibers, the optical fields of the individual waveguides are coupled and correlated with each other. This paper investigates how the refractive index of discrete waveguides can be tuned by thermal diffusion to enhance the coupling between discrete waveguides. In this paper, the discrete waveguide thermally diffused model and the thermally diffused coupling model of twin-core and three-core fibers are constructed. The multicore fiber is heated with a hydrogen-oxygen flame for different times, and the outgoing light field at the end face of the optical fiber is monitored at the same time. Then, the three-dimensional refractive index measurement results of the thermally diffused multicore fiber verify the feasibility of thermal diffusion technology to change the refractive index of discrete waveguides for coupling. Thermal diffusion technology can be used to fabricate multicore fiber couplers. Combined with multicore fiber and core-by-core inscribed fiber Bragg gratings technology, single-channel sensing measurement can be realized by thermal diffusion technology. The method of changing the refractive index of discrete waveguides through thermal diffusion has the advantages of high integration, high stability, and mass fabrication. The research on the thermal diffusion of discrete waveguides can improve the application potential of multicore fiber sensing systems, and promote the broad application of discrete waveguide structure optical fiber in the fields of optical communication, optical sensing, biomedicine, artificial intelligence.