What is the common refractive index profile used in single-mode fiber?

The commonly used refractive index profile in single-mode fiber is the step-index or graded-index profile. This type of profile allows for efficient propagation of light within the fiber core.

In single-mode fibers, the core has a very small diameter, typically around 8 to 10 micrometers, which supports only one mode of light to travel. The step-index profile features a distinct boundary between the core, which has a higher refractive index, and the cladding, which has a lower refractive index. This abrupt change in refractive index minimizes modal dispersion, allows for high bandwidths, and maintains the integrity of the light signal over longer distances.

A graded-index profile, which gradually changes the refractive index from the center of the core to the cladding, is more common in multimode fibers as it helps to reduce modal dispersion by allowing light rays to travel at varying speeds. However, in the context of single-mode fibers, the step-index profile is preferred and widely utilized because it effectively confines the light in the core, ensuring minimal loss and efficient transmission.

Understanding the role of the refractive index profile is crucial for maintaining signal quality and optimizing performance in fiber optic communications.