Fiber optic patch cords are composed of a glass or plastic fiber core, protective cladding, strength members like Kevlar, and an outer jacket made from materials such as PVC, LSZH, or plenum-rated compounds.

Core and Cladding

The fiber core is typically made of high-purity silica glass for single-mode fibers (9 µm diameter) or multimode fibers (50/62.5 µm diameter), which allows light to transmit with minimal loss over long distances . Surrounding the core is the cladding, also made of silica glass but with a lower refractive index, which ensures total internal reflection and keeps the light confined within the core .

Coatings

A primary coating of UV-cured acrylate or resin is applied over the cladding to protect the fiber from physical damage and microbending. Some fibers may have additional secondary coatings for extra protection, especially in outdoor or industrial environments .

Strength Members

To enhance durability, Kevlar (aramid yarn) is used as a strength member under the jacket. Kevlar provides tensile strength, heat resistance, and protection against mechanical stress during installation and handling . In armored patch cords, a stainless steel or flexible metal tube may be added inside the jacket for rodent resistance and extra mechanical protection .

Outer Jacket

The outer jacket protects the fiber and strength members from environmental factors. Common materials include:

• PVC (OFNR): Standard indoor use, flame-retardant .
• LSZH (Low-Smoke Zero Halogen): Reduces toxic smoke in case of fire, suitable for indoor public spaces .
• OFNP (Plenum-rated): For air-handling spaces, highly fire-resistant .
• Specialized jackets: Can be customized for outdoor, industrial, or FTTH applications, including UV-resistant or bend-insensitive designs .

Connectors and Ferrules

The connector housing is usually made of durable plastic or metal, while the ferrule, which aligns the fiber core, is typically made of ceramic (zirconia), stainless steel, or polymer. The ferrule ensures precise light transmission and low insertion loss .

Summary

In essence, a fiber optic patch cord combines:

• Glass or plastic fiber core for light transmission
• Silica cladding for total internal reflection
• Protective coatings for mechanical and environmental protection
• Kevlar or metal strength members for tensile strength
• Outer jacket made of PVC, LSZH, or plenum-rated materials
• Connector housing and ferrule made of plastic, metal, or ceramic for precise alignment . These materials are selected based on the application, whether indoor, outdoor, high-density data centers, or FTTH installations, ensuring durability, safety, and optimal optical performance.