[en] Optical sensors, such as fiber interferometers transmit along light paths and perform measurements based on optical path difference. These types of sensors can reduce device volume and improve sensing performance using optical multiplexing. A beam splitter for optical path multiplexing in an optical fiber ring is proposed. A photonic crystal was used to design the beam splitter. By optimizing and improving the photonic crystal microstructure, the beam splitting function can be realized while taking into account the cycling capability. Therefore, the light can recirculate multiple times in the fiber ring to realize light path multiplexing. The finite difference time domain method is used to analyze and evaluate the performance of the beam splitter.