is sometimes called the total acceptance angle of the fiber.
This result can be derived from Snell's law by considering the critical angle.
The confinement of light by the fiber can also be described in terms of bound modes or guided modes.
This treatment is necessary when considering single-mode fiber, since the ray model does not accurately describe the propagation of light in this type of fiber.
This article incorporates public domain material from Federal Standard 1037C.