What type of ray passes through the axis of the optical fiber?

The correct answer is meridional rays, which are essential in the context of optical fibers. Meridional rays are defined as those that pass through the fiber's core axis and typically involve the central axis of the fiber during their propagation.

In optical fibers, these rays travel directly in line with the core's axial direction and can even reflect internally at the core-cladding boundary, allowing for efficient light transmission. This characteristic enables meridional rays to be part of the primary light transmission mechanisms within the fiber.

In contrast, other ray types, such as skew rays, do not intersect the axis of the fiber and instead propagate in a manner that deviates from the central line, which reduces their effectiveness in transmitting light through the fiber system. Oblique rays also maintain a trajectory that does not intersect the core axis and can result in losses due to improper angles for total internal reflection. Virtual rays represent an abstract concept used in ray optics to describe paths that light may take but do not correspond to actual light traveling in the system.

Understanding the unique behavior of meridional rays is critical for optimizing optical fiber performance and ensuring efficient data transmission in various applications.