Single-mode optical fiber can be divided into several categories based on ITU-T and IEC standards, including G.652, G.653, G.654, G.655, G.656, and G.657, each optimized for specific transmission characteristics and applications.

ITU-T Standard Single-Mode Fibers

1. G.652 (Dispersion-Unshifted Fiber)
   • Most widely used single-mode fiber.
   • Suitable for general-purpose applications, including long-haul and metro networks.
   • Available in subtypes A, B, C, and D, differing in polarization mode dispersion (PMD) and water peak characteristics.
   • Operates efficiently at 1310 nm and 1550 nm wavelengths .
2. G.653 (Dispersion-Shifted Fiber)
   • Designed to shift zero-dispersion wavelength to 1550 nm for long-distance single-channel transmission.
   • Less commonly used today due to nonlinear effects in WDM systems .
3. G.654 (Cutoff Wavelength-Shifted Fiber)
   • Optimized for long-distance transmission with minimal attenuation at 1550 nm.
   • Commonly used in submarine cables and ultra-long-haul networks .
4. G.655 (Nonzero Dispersion-Shifted Fiber)
   • Maintains small but nonzero dispersion at 1550 nm to reduce nonlinear effects in dense WDM systems.
   • Ideal for high-capacity long-haul networks .
5. G.656 (Wideband Fiber)
   • Ensures stable transmission over a broader wavelength range, supporting DWDM systems.
   • Suitable for metro and regional networks requiring multiple wavelength channels .
6. G.657 (Bend-Insensitive Fiber)
   • Designed for tight bending with a minimum bend radius of 5–10 mm.
   • Widely used in FTTH (Fiber to the Home) and indoor installations where space constraints exist .

IEC Standard Single-Mode Fibers

• IEC classifies single-mode fibers into types such as B1.1, B1.2, B1.3, B2, and B4, which correspond to ITU-T standards and define core/cladding dimensions, cutoff wavelengths, and dispersion properties.
• These classifications ensure compatibility and performance consistency across international networks .

Specialized Single-Mode Fibers

• Dispersion-Shifted and Nonzero Dispersion-Shifted Fibers: Engineered to manage chromatic dispersion for high-speed and long-distance WDM systems.
• Bend-Insensitive Fibers: Optimized for indoor, FTTH, and high-density cabling environments.
• Hollow-Core and Few-Mode Fibers: Emerging designs for ultra-low latency and high-capacity transmission, though less common commercially .

Applications

• Backbone networks, long-haul and submarine communications, metro networks, and FTTH deployments.
• Single-mode fibers eliminate modal dispersion, enabling high-bandwidth transmission over continental and transoceanic distances . In summary, single-mode optical fibers are categorized primarily by ITU-T and IEC standards, with each type tailored for specific wavelength ranges, dispersion characteristics, and installation environments, ensuring optimal performance for diverse optical communication applications.