The Science Behind Optical Fibers
When a ray of light light enters a dense medium, such as plastic or glass, it is refracted, or directed in a different direction than its original path.
Every medium that light can pass through has a critical angle, or maximum angle such that light entering it is transmitted without being absorbed. This critical angle is dependent on the refractive indices of both mediums.
Fiber optics is the use of transparent, flexible fiber to transmit light from one end to the other.
Fiber optic communication begins with converting an electrical signal to light. This light, generated by a laser diode (LD) or light emitting diode (LED) is transmitted through one end of an optical fiber and received on the other by a photodiode.
Fiber optics leverages the total internal reflection properties of optical fiber, which is also a function of the refractive index of the fiber’s core and its cladding. With the right ratio between the two, light from one end is reflected at the mediums’ boundary, or interface, and guided through the length of the fiber.
Optical physics is the primary field of study that concerns fiber optics. Many of the fundamental principles of RF transmission line theory, such as attenuation, insertion loss, return loss, and dispersion, also apply.
Fibers and other transmission media are evaluated by numerical aperture (NA), which is the sine of the critical angle. The larger numerical aperture, the less precisely fiber cores can be aligned with transmitters, receivers, and other fibers for light to be transmitted effectively.