The main light sources commonly used in fiber optic communication are

The most commonly used light sources in fiber optic communication are Light Emitting Diodes (LEDs) and semiconductor laser diodes, with specific wavelengths chosen for short- or long-distance transmission.

Light Emitting Diodes (LEDs)

LEDs are semiconductor devices that emit light when an electric current passes through them. They are typically used in short-distance, low-speed fiber optic systems due to their broad spectral width, lower cost, and robustness . LEDs emit light over a range of wavelengths, commonly 850 nm to 1300 nm, which is suitable for multimode fiber applications . Their non-coherent, diffuse light makes them less efficient for long-distance transmission because of chromatic dispersion and lower optical power .

Semiconductor Laser Diodes

Laser diodes are preferred for long-distance, high-speed communication because they produce coherent, narrow spectral width light with higher intensity . Common materials include gallium arsenide (GaAs), gallium aluminum arsenide (GaAlAs), and indium gallium arsenide phosphide (InGaAsP), which emit at wavelengths such as 850 nm, 1300 nm, and 1550 nm . The 1300 nm and 1550 nm wavelengths are particularly favored for long-haul systems due to low fiber loss and minimal pulse dispersion, with 1550 nm also compatible with optical amplifiers for extended distances .

Broadband Light Sources

Broadband light sources (BLS) generate light over a wide range of wavelengths and are sometimes used in specialized fiber optic systems, such as erbium-doped fiber amplifiers or near-infrared spectroscopy . While they provide high-speed capabilities and broad spectral coverage, they are generally replaced by laser diodes in most modern communication systems due to the latter's coherent and nearly monochromatic output .

Summary

• Short-distance, low-speed systems: LEDs (850–1300 nm)
• Long-distance, high-speed systems: Semiconductor laser diodes (1300–1550 nm)
• Specialized applications: Broadband light sources (near-IR, wide spectral range) These light sources are selected based on distance, speed, fiber type, and wavelength-dependent loss and dispersion characteristics to optimize the performance of fiber optic communication networks .