Inside the hollow, HCF features an air-filled center channel that is surrounded by a ring of tubes, akin to a honeycomb pattern. The only glass involved is on the outside structure of the cable itself. However, glass imposes a fundamental physical limitation because light travels through it approximately 30 percent slower than through air. In standard silica. Hollow-core optical fibers (HCFs) have unique properties like low latency, negligible optical nonlinearity, wide low-loss spectrum, up to 2100 nm, the ability to carry high power, and potentially lower loss then solid-core single-mode fibers (SMFs). These features make them very promising for. Abstract: This paper describes a newly developed butt joint type hollow-core fiber connector with protected fiber ends. 5 dB attenuation and a 45 dB return loss without physical contact.