Fiber optic communication is classified by wavelength into standardized bands, primarily 850 nm, 1300/1310 nm, and 1550 nm, with additional ITU-defined bands for WDM applications.

Standard Transmission Wavelengths

Fiber optic systems are designed to operate at specific wavelengths where the fiber exhibits minimal loss and optimal performance. The most commonly used wavelengths are:

• 850 nm: Typically used in multimode fibers, especially for short-distance applications such as local area networks (LANs) due to acceptable attenuation and compatibility with inexpensive LEDs or VCSELs .
• 1300/1310 nm: Used in singlemode fibers for medium-distance communication, offering lower attenuation and reduced dispersion compared to 850 nm .
• 1550 nm: Preferred for long-distance and high-capacity networks, including backbone and metropolitan area networks, because it has the lowest attenuation in silica fibers and supports dense wavelength division multiplexing (DWDM), . Plastic optical fibers (POF) often use 650 nm for short-range applications due to lower absorption in plastic materials .

Wavelength Bands and ITU Classification

The International Telecommunication Union (ITU) has standardized wavelength bands to ensure interoperability and efficient use of fiber capacity. Key bands include:

• O-band (Original band, 1260–1360 nm): Low dispersion, suitable for early singlemode systems.
• E-band (Extended band, 1360–1460 nm): Less commonly used, avoids water absorption peaks.
• S-band (Short wavelength band, 1460–1530 nm): Emerging applications in DWDM.
• C-band (Conventional band, 1530–1565 nm): Most widely used for long-haul DWDM systems due to low attenuation and compatibility with erbium-doped fiber amplifiers (EDFAs).
• L-band (Long wavelength band, 1565–1625 nm): Extends capacity for DWDM systems.
• U-band (Ultra-long wavelength band, 1625–1675 nm): Specialized applications, less common .

Factors Influencing Wavelength Choice

The selection of a wavelength depends on several physical and practical factors:

• Attenuation: Shorter wavelengths scatter more (Rayleigh scattering), while longer wavelengths may encounter absorption from water or other impurities in the fiber .
• Dispersion: Different wavelengths travel at slightly different speeds, affecting signal integrity over long distances.
• Source and detector availability: Lasers and photodetectors are optimized for specific wavelengths, making certain bands more practical .
• Multiplexing capability: WDM systems rely on multiple wavelengths to transmit data simultaneously through a single fiber, requiring precise wavelength allocation .

Summary

Fiber optic communication is classified by wavelength to optimize performance, minimize loss, and enable advanced multiplexing techniques. 850 nm, 1300/1310 nm, and 1550 nm are the primary transmission wavelengths, while ITU-defined bands (O, E, S, C, L, U) provide a framework for modern WDM systems. Understanding these classifications is essential for designing, testing, and deploying reliable fiber optic networks .