What is the typical light source for single-mode fiber optic cables?

The typical light source for single-mode fiber optic cables is laser diodes. Single-mode fibers have a small core diameter (about 8 to 10 microns), which allows only one mode of light to propagate through the fiber. This narrow core size significantly reduces modal dispersion, making the transmission of data over long distances much more efficient and effective.

Laser diodes emit light that is highly focused and has a specific wavelength, often in the near-infrared spectrum (commonly around 1310 nm or 1550 nm). This property makes them ideal for single-mode fibers, as the coherent light from lasers can travel longer distances with minimal loss and is less affected by scattering compared to other light sources.

In contrast, light-emitting diodes (LEDs) emit light over a broader range of wavelengths and are typically used with multimode fiber optic cables, which have larger core diameters and can support multiple modes of light. Incandescent bulbs and fluorescent lamps are not practical for optical fiber applications, as they do not provide the necessary coherence or wavelength specificity required for efficient transmission in single-mode fibers.