Design and analysis of all-fiber mode filter based on multi-core fiber

We propose an all-fiber mode filter based on multi-core fiber, which efficiently selects or filters out specific modes. Based on the mode coupling principle, we designed all-fiber mode filters using dual-core fiber (DCF) and three-core fiber (TCF) structures to achieve multifunctional mode filtering. In the DCF structure, any mode can be filtered out; taking 1550 nm as the working wavelength, the mode filter achieves remarkable efficiency exceeding 90% for LP 01 , LP 11 and LP 21 modes, achieving bandwidths of approximately 110 nm, 117 nm, and 117 nm, respectively. In the TCF structure, the beam containing LP 11 , LP 21 and LP 31 modes is transmitted, filtering out both the LP 11 and LP 21 modes while maintaining high transmission of the LP 31 mode, and the transmission ratio can reach 90%. To the best of our knowledge, this is the first report on mode filter based on all-fiber structure. This method offers the promising solutions for advanced optical communication systems and photonic device integration.