G.655 fiber optic cable is a single-mode fiber, specifically designed for long-haul and DWDM systems, with non-zero dispersion to reduce nonlinear effects.

Overview of G.655 Fiber

G.655 is an ITU-T standardized single-mode optical fiber known as non-zero dispersion-shifted fiber (NZ-DSF), engineered to support dense wavelength division multiplexing (DWDM) and long-haul transmission systems while minimizing nonlinear impairments . It has a mode field diameter of 8–11 µm and operates in the C and L bands, making it suitable for high-capacity backbone networks . The fiber is inherently single-mode, guiding light through a narrow core using total internal reflection, which ensures single-mode operation across the specified wavelength range .

Key Characteristics

• Chromatic Dispersion: G.655 fibers maintain a non-zero dispersion coefficient across 1530–1565 nm, reducing four-wave mixing and other nonlinear effects in DWDM systems .
• Polarization Mode Dispersion (PMD): G.655.C fibers have a maximum PMD link design value of 0.20 ps/√km, providing low signal distortion .
• Attenuation: Typical attenuation is low in the C and L bands, supporting long-distance transmission.
• Mechanical and Environmental Performance: High-quality G.655 cables are designed to withstand bending, temperature variations, and mechanical stress, ensuring long-term reliability, often rated for 25 years of service .

Applications

G.655 fiber is widely used in:

• Long-haul backbone networks
• Submarine and terrestrial DWDM systems
• High-capacity metro networks
• Optical Ground Wire (OPGW) installations

Comparison with Other Single-Mode Fibers

• G.652: Standard single-mode fiber, optimized for general-purpose metro and access networks.
• G.655: Non-zero dispersion-shifted, optimized for long-haul DWDM to reduce nonlinear effects.
• G.657: Bend-insensitive fiber, ideal for FTTH and tight-radius indoor installations .

Assurance of Single-Mode Operation

G.655 fiber is guaranteed single-mode by design, as defined in the ITU-T G.655 standard. Its core size, refractive index profile, and dispersion properties ensure that only the fundamental mode propagates efficiently, making it fully compatible with single-mode network equipment . High-quality manufacturers also perform ISO-certified quality control and mechanical/environmental testing to maintain single-mode performance throughout the cable's service life . In summary, G.655 fiber optic cable is a reliable, guaranteed single-mode solution for high-capacity, long-distance optical networks, offering low PMD, controlled dispersion, and robust mechanical performance.