Fiber optic communication primarily uses wavelengths of 850 nm, 1300/1310 nm, and 1550 nm, chosen for low attenuation and optimal transmission performance.

Standard Transmission Wavelengths

• 850 nm: Commonly used in multimode fiber for short-distance applications, typically with LED or VCSEL light sources. It offers acceptable attenuation and is cost-effective for local area networks (LANs) and data centers .
• 1300/1310 nm: Used in both multimode (1300 nm) and single-mode (1310 nm) fibers. This wavelength provides lower chromatic dispersion, allowing signals to travel longer distances without significant distortion .
• 1550 nm: Predominantly used in single-mode fiber for long-haul and high-capacity networks. It has the lowest attenuation in standard silica fibers and is compatible with Erbium-Doped Fiber Amplifiers (EDFAs), making it ideal for long-distance transmission .

Wavelength Bands

The International Telecommunication Union (ITU) defines several wavelength bands for fiber optics:

• O-band (Original, ~1260–1360 nm): Early optical communication, low chromatic dispersion, higher attenuation.
• E-band (Extended, ~1360–1460 nm): Developed to increase bandwidth; initially limited by water peak absorption.
• S-band (Short, ~1460–1530 nm): Lower attenuation than O-band, used in some metro networks.
• C-band (Conventional, ~1530–1565 nm): Most widely used for long-haul WDM systems due to low loss and EDFA compatibility.
• L-band (Long, ~1565–1625 nm): Extends capacity for WDM systems.
• U-band (Ultra-long, ~1625–1675 nm): Less common, used for specialized applications .

Role of Wavelength in WDM

Wavelength Division Multiplexing (WDM) allows multiple optical signals at different wavelengths to travel simultaneously over a single fiber, increasing capacity without additional fiber.

• Coarse WDM (CWDM): Uses wider channel spacing, suitable for shorter distances, often in O- and E-bands.
• Dense WDM (DWDM): Uses narrow channel spacing, enabling hundreds of channels over long distances, mainly in C- and L-bands .

Summary

The choice of wavelength in fiber optics balances attenuation, dispersion, and component availability. Multimode fibers favor 850 nm and 1300 nm, while single-mode fibers favor 1310 nm and 1550 nm. For high-capacity, long-distance networks, C-band and L-band are standard due to low loss and compatibility with optical amplifiers. WDM technologies further exploit these wavelengths to maximize fiber utilization .