Asymmetric Curvature Side-polished Optical Fiber Coupler

• Published in: IEEE photonics journal 2023-08, Vol.15 (4), p.1-6
• Main Authors: Uematsu, Takui, Noto, Kazutaka, Iida, Hiroyuki, Fukai, Chisato, Ogushi, Ikutaro
• Format: Article
• Language: English
• Subjects: Asymmetric structures; Couplers; Insertion loss; Optical coupling; Optical fiber coupler; Optical fiber couplers; Optical fibers; Passive optical networks; Polishing; Radius of curvature; Refractive index; side-polished fiber; Workability
• ISSN: 1943-0655; 1943-0647
• DOI: 10.1109/JPHOT.2023.3293657

An optical fiber coupler composed of two side-polished fibers with different curvature is proposed. The live-fiber is polished with a typical radius of curvature of 0.25 m, while the branch-fiber is polished with a larger radius of curvature. Analysis shows that the proposed asymmetric structure improves the highest cross-transmission of the coupled light by up to 0.26 just by increasing the curvature of the branch-fiber (compared to the conventional symmetric arrangement) without increasing the insertion loss created by side-polishing. Experiments confirm that the proposed structure raises the highest cross-transmission by 0.15 on average when the curvature of the branch-fiber is set to 0.5 m while the curvature of the live-fiber is kept to the typical value as expected from the analysis. Our study will contribute to realizing a simple and compact machine for polishing live-fibers that offers the improved workability and portability needed for adding optical fiber couplers to live-fibers in the field.