Single-mode fiber optic systems typically use ________ light sources.

Single-mode fiber optic systems are designed to transmit optical signals over long distances with minimal signal loss and distortion. These systems typically operate at wavelengths around 1310 nm and 1550 nm. The light source used for single-mode systems is primarily the laser diode, which is a coherent light source. Laser diodes emit a narrow beam of light that maintains a consistent phase relationship, allowing for greater precision in transmission over longer distances.

The use of laser diodes in single-mode fibers ensures that the light travels through the core of the fiber without significant dispersion, which is crucial for maintaining the integrity of the signal over long runs. This characteristic makes laser diodes the preferred choice for such applications since they can efficiently couple light into the small core diameter typical of single-mode fibers.

While other options, like LEDs or different types of lasers, have their own applications, they do not align with the performance requirements for single-mode fiber optic systems. LEDs, for instance, produce a broader spectrum of light and are better suited for multimode systems, where the higher level of dispersion can be managed effectively.