Optical fiber communication primarily uses wavelengths in the infrared region, typically around 850 nm, 1310 nm, and 1550 nm, corresponding to standardized bands for efficient, low-loss transmission.

Standard Wavelength Bands

Optical fiber systems operate within specific wavelength bands standardized by the International Telecommunication Union (ITU) to optimize performance:

• O-band (Original Band): ~1260–1360 nm, used for early optical systems; minimal chromatic dispersion but higher attenuation.
• E-band (Extended Band): ~1360–1460 nm, developed to expand bandwidth; historically limited by water peak absorption.
• S-band (Short Wavelength Band): ~1460–1530 nm, lower attenuation than O-band, used in some long-haul and metro networks.
• C-band (Conventional Band): ~1530–1565 nm, the most widely used band due to lowest fiber attenuation and compatibility with Erbium-Doped Fiber Amplifiers (EDFAs).
• L-band (Long Wavelength Band): ~1565–1625 nm, used to extend capacity in long-haul networks alongside C-band.
• U-band (Ultra-Long Band): ~1625–1675 nm, less common, used for specialized applications or research purposes .

Typical Operating Wavelengths

• Multimode fiber: Short-distance applications, typically use 850 nm or 1300 nm light sources such as LEDs or VCSELs. Modal dispersion limits long-distance performance .
• Single-mode fiber: Long-distance and high-bandwidth applications, typically use 1310 nm or 1550 nm lasers. These wavelengths minimize attenuation and chromatic dispersion, allowing transmission over tens to hundreds of kilometers .

Transmission Windows and Attenuation

Fiber attenuation is lowest in the 1310 nm and 1550 nm windows, making these wavelengths ideal for long-distance communication. Longer wavelengths generally experience lower attenuation, while shorter wavelengths like 850 nm are suitable for shorter links. Infrared wavelengths are chosen because they fall between absorption bands in the fiber, avoiding water and metallic impurity absorption peaks .

Wavelength Division Multiplexing (WDM)

Modern networks often use WDM, which allows multiple wavelengths to be transmitted simultaneously over a single fiber. Each wavelength acts as a separate channel, significantly increasing network capacity without additional fiber deployment. WDM systems typically operate within the C-band and L-band for long-haul, high-capacity networks . In summary, optical fiber communication relies on infrared wavelengths between 850 nm and 1625 nm, with specific bands chosen to balance attenuation, dispersion, and compatibility with optical components, enabling efficient and high-capacity data transmission over varying distances.