A typical 4-core single-mode optical cable has an outer diameter of around 5.8 mm, contains four single-mode fibers in a loose or tight buffer, and includes strength members such as FRP or aramid yarn for durability.

Cable Structure and Components

• Optical Fibers: Four single-mode fibers, each with a doped silica core and concentric silica cladding, coated with a dual-layer UV-cured acrylate for mechanical protection and low micro-bending loss .
• Buffer Tube: Fibers are housed in a loose or tight buffer tube, often gel-filled for moisture protection. The nominal outer diameter of the buffer tube is typically 2.8 ± 0.1 mm, with a minimum wall thickness of 0.4 mm .
• Strength Members: Fiber Reinforced Plastic (FRP) rods or multi-strand aramid yarn (Kevlar) are included to prevent stretching and provide tensile strength, especially for outdoor installations .
• Outer Jacket: The cable is protected by a PE (Polyethylene) jacket for outdoor use or LSZH (Low Smoke Zero Halogen) for indoor safety. The overall cable diameter is generally around 5.8 mm .

Mechanical and Environmental Specifications

• Proof Test: Each fiber is proof-tested to 100 kpsi to ensure durability under installation stress .
• Temperature and Environmental Resistance: The dual acrylate coating and gel-filled buffer tube provide resistance to micro-bending, abrasion, hydrolytic degradation, and long-term aging .
• Color Coding: Fibers follow the TIA-598-C standard color sequence: Blue, Orange, Green, Brown for the first four fibers, facilitating splicing and termination .

Performance Characteristics

• Wavelength Compatibility: Single-mode fibers typically operate at 1310 nm, 1550 nm, and sometimes 1625 nm for testing purposes .
• Applications: Ideal for FTTH, GPON, CATV, and high-speed internet connectivity, supporting duplex links and redundancy configurations .
• Testing: Cables are tested using OTDR to verify splice loss, measure length, and detect faults . In summary, a 4-core single-mode optical cable is a compact, high-performance cable designed for reliable data transmission, with a 5.8 mm outer diameter, robust protective layers, and standardized fiber color coding for easy installation and maintenance.