Single mode fiber: the central glass core is very thin (the core diameter is generally 9 or 10) μ m) , only one mode of optical fiber can be transmitted.
The intermodal dispersion of single-mode fiber is very small, which is suitable for remote communication, but there are also material dispersion and waveguide dispersion. In this way, the single-mode fiber has high requirements for the spectral width and stability of the light source, that is, the spectral width should be narrow and the stability should be good.
Later, it was found that on 1.31 μ At M wavelength, the material dispersion and waveguide dispersion of single-mode fiber are positive and negative, and the size is exactly the same. So, 1.31 μ M wavelength region has become a very ideal working window of optical fiber communication, and it is also the main working band of practical optical fiber communication system 1.31μM the main parameters of conventional single-mode fiber are determined by ITU-T in G652 recommendation, so this kind of fiber is also called G652 fiber.
Compared with multimode fiber, single-mode fiber can support longer transmission distance. In 100Mbps Ethernet and 1G gigabit network, single-mode fiber can support transmission distance of more than 5000m.
From the perspective of cost, because the optical transceiver is very expensive, the cost of using single-mode optical fiber will be higher than that of multi-mode optical fiber cable.
The refractive index distribution is similar to that of mutant fiber, and the core diameter is only 8 ~ 10 μ m. The light propagates along the central axis of the fiber core in a linear shape. Because this kind of fiber can only transmit one mode (degeneracy of two polarization states), it is called single-mode fiber, and its signal distortion is very small.
Explanation of “single-mode optical fiber” in academic literature: generally, when V is less than 2.405, only one wave crest passes through the optical fiber, so it is called single-mode optical fiber. Its core is very thin, about 8-10 microns, and the mode dispersion is very small. The main factor affecting the transmission band width of optical fiber is various dispersion, and the mode dispersion is the most important, and the dispersion of single-mode optical fiber is small, Therefore, light can be transmitted for a long distance in a wide frequency band.
The single-mode optical fiber has a core diameter of 10 microns, which can allow single-mode beam transmission and reduce the limitations of bandwidth and modal dispersion. However, due to the small core diameter of single-mode optical fiber, it is difficult to control beam transmission, so it needs extremely expensive laser as the light source, and the main limitation of single-mode optical fiber lies in material dispersion, Single mode optical cable mainly uses laser to obtain high bandwidth. Because LED will emit a large number of light sources with different bandwidth, the material dispersion requirement is very important.
Compared with multimode fiber, single-mode fiber can support longer transmission distance. In 100Mbps Ethernet and 1G gigabit network, single-mode fiber can support transmission distance of more than 5000m.
From the perspective of cost, since the optical transceiver is very expensive, the cost of using single-mode optical fiber will be higher than that of multi-mode optical fiber cable.
Single mode fiber (SMF)
Compared with multimode fiber, the core diameter of single-mode fiber is much thinner, only 8 ~ 10 μ m。 Because only one mode is transmitted, there is no inter mode dispersion, small total dispersion and wide bandwidth. Single mode fiber is used in 1.3 ~ 1.6 μ In the wavelength region of M, through the appropriate design of the refractive index distribution of the optical fiber and the selection of high-purity materials to prepare a cladding 7 times larger than the core, the minimum loss and minimum dispersion can be achieved at the same time in this band.
Single mode optical fiber is used in long-distance and high-capacity optical fiber communication system, optical fiber local area network and various optical fiber sensors
Post time: Mar-08-2022