Transmission distance of single-mode optical fiber: 64 channels of 40G Ethernet can be transmitted up to 2,840 miles on a single-mode optical fiber cable. Single-mode optical fiber is mainly composed of core, cladding and coating layer; the core is made of highly transparent material; the refractive index of the cladding is slightly smaller than the core, resulting in an optical waveguide effect that makes most The electromagnetic field is bound in the fiber core for transmission; the function of the coating layer is to protect the fiber from water vapor erosion and mechanical abrasion, and at the same time increase the flexibility of the fiber. Outside the coating layer, a plastic jacket is often added.
What is the difference between single mode fiber and multimode fiber?
Different refractive index: Single-mode fiber mostly adopts step refractive index distribution. Multimode optical fiber can adopt step-index distribution or graded-index distribution; therefore, silica fiber can also adopt multi-mode step-index fiber, multi-mode graded-index fiber and single-mode step-index fiber in general. three kinds.
Different transmission modes: single-mode fiber can only transmit one mode for a given working wavelength, and multimode fiber can transmit several modes. The propagation of electromagnetic waves such as light in the optical fiber belongs to the medium circular waveguide. When the light is totally reflected at the interface of the medium, the electromagnetic wave is confined in the medium, which is called guided wave or guided mode. For a given guided wave and working wavelength, there are many incident situations that satisfy the condition of total reflection, which are called different modes of the guided wave. According to the transmission mode, it is divided into multimode fiber and single mode fiber.
The difference in transmission distance: The transmission distance and transmission bandwidth of single-mode fiber are obviously due to that of multimode fiber. If the transmission distance is greater than 5 kilometers, it is long to choose single-mode fiber for transmitting large broadband data signals in applications; if the transmission distance is only a few kilometers, then multi-mode is the best choice, because LED transmitter/receiver requires more laser than single-mode much cheaper.
Different wavelengths of optical fiber transmission: the core diameter of single-mode optical fiber is very small, and it can only transmit in a single mode at a given working wavelength, with wide transmission frequency and large transmission capacity. Multimode fiber is an optical fiber that can simultaneously transmit in multiple modes at a given operating wavelength. Compared with single-mode fiber, the transmission performance of multimode fiber is poor.
