1.optical fiber core structure
1) Core: high refractive index, used to transmit light;
2) Cladding: low refractive index, forming a total reflection condition with the core;
3) Protective layer: protects the optical fiber.
2.Single-mode and multi-mode
Only one mode of light can be transmitted. Therefore, its inter-mode dispersion is small and suitable for remote communication, but there are also material dispersion and waveguide dispersion. In this way, single-mode fiber has higher requirements for the spectral width and stability of the light source, that is, the spectral width must be narrow and the stability Better. Single-mode fiber has zero total dispersion.
Can transmit multiple modes of light. However, its inter-mode dispersion is large, which limits the frequency of transmitting digital signals, and it will become more serious with increasing distance. Multi-mode fiber transmission distance is relatively short, generally only a few kilometers.
Single-mode equipment can usually run on single-mode fiber or multi-mode fiber, while multi-mode equipment is limited to running on multi-mode fiber.