Optical fiber is usually a glass solid fiber drawn from SiO2 as the matrix material, which is widely used in optical fiber communications. The principle of light guiding is the mechanism of total internal reflection of light. That is, when the light is incident from the light-dense medium with a large refractive index to an optically sparser medium with a small refractive index at an angle greater than the critical angle, total reflection will occur, and the incident light will all be reflected to the light-dense medium with a large refractive index, and the refractive index is small.
Fiber can be divided into single-mode fiber and multi-mode fiber. Single-mode fiber has a small core diameter and can transmit only one mode of light, with small inter-mode dispersion. The core diameter of multi-mode fiber is thick, which can transmit multiple modes of light, but the dispersion between modes is relatively large.
The transmission mode of the fiber laser is to use the fiber to conduct laser beam. Generally speaking, the principle is to wrap a layer of YAG crystal in the inner and outer circles of the optical fiber, so that the light source can illuminate the YAG crystal from the optical fiber to generate laser, and at the same time, repeated refraction conduction is carried out in the optical fiber.