The butterfly-shaped optical cable contains several coatings

Butterfly-shaped optical cables contain multiple protective and functional coatings, including primary fiber coatings, a butterfly cable sheath, foaming filling layers, and an outer sheath with embedded fiber yarns.

Fiber-Level Coatings

The optical fibers inside the butterfly cable are first coated with primary and secondary coatings, typically acrylate-based polymers. The inner coating is softer to absorb mechanical stress, while the outer coating is harder to provide chemical and mechanical durability. These coatings protect the glass fiber from microbending, tensile stress, moisture, and environmental damage, and they are applied immediately after fiber drawing using UV-curable processes . Some specialty fibers may also use high-temperature acrylates, silicone, or fluoroacrylate coatings for enhanced chemical and thermal resistance .

Butterfly Cable Sheath

Surrounding the optical fibers is the butterfly-shaped cable sheath, which provides structural support and mechanical protection. This sheath often includes tearing grooves to facilitate easy access to the fibers during installation . Reinforcing members may be embedded within the sheath to improve compression and impact resistance.

Foaming Filling Unit

Between the butterfly cable sheath and the outer sheath, a foaming filling unit is applied. This layer enhances compression resistance, impact resistance, thermal insulation, and water resistance. The foaming filling may be coated with hot melt adhesive and include water-blocking powders to prevent moisture ingress . It is often divided into multiple subunits to optimize mechanical performance and flexibility.

Outer Sheath and Fiber Yarns

The outer sheath of the cable is typically elliptical and contains a rectangular inner cavity that houses the butterfly cable unit. Fiber yarns are embedded symmetrically around the cable unit to provide additional tensile strength and bending flexibility . The outer sheath also serves as a protective barrier against environmental hazards, UV exposure, and physical strain, ensuring long-term signal integrity .

Summary

In essence, a butterfly-shaped optical cable is a multi-layered system where each coating and layer serves a specific purpose: the fiber coatings protect the glass core, the butterfly sheath provides structural support, the foaming filling enhances mechanical and environmental resistance, and the outer sheath with fiber yarns ensures durability and flexibility. This combination allows the cable to maintain signal integrity, ease of installation, and long-term reliability in FTTH and other fiber-optic applications .