Long-distance optical cables are typically single-mode fibers with low attenuation, minimal dispersion, and compliance with ITU-T G.652, G.655, or G.657 standards.

Fiber Type and Core Characteristics

Long-distance optical cables predominantly use single-mode fiber (SMF), which has a core diameter of approximately 8–10 µm, minimizing modal dispersion and enabling transmission over distances up to 100 km without regeneration . The most common fiber types include:

• G.652.D: Standard single-mode fiber with low attenuation and full-spectrum capability, suitable for long-haul, metro, and backbone networks .
• G.655: Non-zero dispersion-shifted fiber optimized for DWDM systems, reducing nonlinear effects over long distances .
• G.657: Bend-insensitive fiber compatible with G.652, ideal for installations requiring tight bends or constrained spaces .

Wavelength and Attenuation

Long-distance fibers typically operate at 1310 nm and 1550 nm, where silica fiber exhibits minimal loss. Attenuation values are generally:

• <0.4 dB/km at 1310 nm
• <0.3 dB/km at 1550 nm These low-loss characteristics allow long-distance transmission without frequent signal amplification .

Dispersion and Bandwidth

• Chromatic dispersion is a critical factor for long-haul transmission. G.652 fibers have near-zero dispersion at 1310 nm, while G.655 fibers maintain controlled non-zero dispersion at 1550 nm to support DWDM systems .
• Bandwidth is virtually unlimited for practical applications, ensuring future-proofing for higher data rates .

Cable Construction

Long-distance optical cables are designed for environmental resilience and installation flexibility:

• Loose tube designs (e.g., GYXTW, GYTS/GYTA) for aerial or duct deployment.
• ADSS (All-Dielectric Self-Supporting) for aerial installations without metallic support.
• Armored variants (e.g., GYFTZY) for direct burial or harsh environments .
• Jacket materials include LSZH, PVC, or armored coatings depending on environmental and safety requirements .

Standards Compliance

Key international standards ensure performance and interoperability:

• ITU-T G.652, G.655, G.657: Define optical, geometrical, and transmission characteristics for single-mode fibers .
• IEC 60793-2-50: Fiber specifications for long-distance applications .
• IEC 60794: Cable construction and environmental performance .
• Telcordia GR-20: Reliability and mechanical performance for telecom-grade cables .

Summary

For long-distance optical communication, the ideal cable features single-mode fiber with low attenuation, controlled dispersion, and compliance with international standards, combined with a robust cable design suitable for the deployment environment. Selection should consider fiber type (G.652.D, G.655, G.657), operating wavelength, attenuation, dispersion, and mechanical protection to ensure reliable, high-capacity transmission over extended distances .