Design and analysis of polarization-splitting low-loss rectangular fiber

In this paper, a polarization splitting square fiber is designed to make up for some defects of Dtype fiber in common fiber devices. Compared with D-type optical fiber, square-type optical fiber can be directly drawn by processing the optical fiber preform. Thereby eliminating the need to process the micron-level optical fiber, while maintain the original core-cladding structure. Most of the optical field energy is still limited to the core, which can greatly reduce the insertion loss of the devices. Using the finite element method, the half-length core distance (30 to 90 microns), radius of arc (1 to 9 microns), numerical aperture (0.18 to 0.24) and isolation thickness (0.1 to 2 microns) of the square fiber are optimized. Theoretical calculation results show that under the optimal parameters, the mode loss of our designed square fiber under X polarization is 0.0179dB/mm. And under Y polarization, the mode loss is 0.0454dB/mm. In addition, the mode mismatch loss is 7.506%. This value will reduce the mode loss by 100 times compared with D-type fiber and make full use of the advantages of good coupling to the allfiber system.