A multi-core fiber coupler without a central core

An efficient method for fabricating multi -core fiber couplers based on the thermal diffusion technique is proposed to realize the connection of single -mode fibers to multi -core fibers without a central core. The fabrication efficiency of the multi -core fiber coupler is improved by fiber -loaded hydrogen. The simulation results show that the single -mode fiber and the multi -core fiber can be coupled stably and efficiently by using the designed doubleclad fiber to connect the single -mode fiber and the multi -core fiber. Double -clad fiber and multi -core fiber were loaded with hydrogen to enhance the dopant diffusion rate. Three-dimensional refractive index measurements of the multi -core fiber coupler show that the dopant diffusion rate and the diffusion zone length of the hydrogenloaded fiber are significantly increased compared to the original fiber. These enhancements contributed to the shorter fabrication time of multi -core fiber couplers. The multi -core fiber couplers fabricated by thermal diffusion technology have the advantages of high coupling efficiency, high integration, simple manufacture, and high mechanical strength. Enhancing the diffusion rate of optical fibers by using the hydrogen loading method will increase the application potential of multi -core optical fiber couplers prepared by thermal diffusion technology, and accelerate the translation of multi -core fibers toward optical communication and optical fiber sensing.