Single-mode fiber (SingleModeFiber): The central glass core is very thin (the core diameter is generally 9 or 10μm), and only one mode of fiber can be transmitted.
Single-mode fiber has very small inter-mode dispersion and is suitable for long-distance communication, but it also has material dispersion and waveguide dispersion. In this way, single-mode fiber has higher requirements on the spectrum width and stability of the light source, that is, the spectrum width should be narrow and stable. Sex is better.
Later, it was discovered that at a wavelength of 1.31μm, the material dispersion and waveguide dispersion of the single-mode fiber were positive and negative, and the magnitudes were exactly the same. In this way, the 1.31μm wavelength region has become an ideal working window for optical fiber communication, and it is also the main working band of the current practical optical fiber communication system. The main parameters of 1.31μm conventional single-mode optical fiber are established by the International Telecommunication Union ITU-T in G652. It is determined in the proposal, so this fiber is also called G652 fiber.
Compared with multi-mode fiber, single-mode fiber can support longer transmission distance. From 100Mbps Ethernet to 1G Gigabit network, single-mode fiber can support transmission distance of more than 5000m.
From a cost point of view, since the optical transceiver is very expensive, the cost of using single-mode fiber will be higher than that of multi-mode fiber optic cables.
The refractive index distribution is similar to that of the abrupt fiber, the core diameter is only 8-10 μm, and the light propagates in the direction of the central axis of the core in a straight shape. Because this fiber can only transmit one mode (the two polarization states are degenerate), it is called a single-mode fiber, and its signal distortion is very small.
“Single-mode fiber” is explained in academic literature: Generally, when v is less than 2.405, only one wave crest passes through the fiber, so it is called single-mode fiber. Its core is very thin, about 8-10 microns. The dispersion is very small. The main factors that affect the width of the optical fiber transmission band are various dispersions, and the modal dispersion is the most important. The dispersion of single-mode fibers is small, so it can transmit light in a wide frequency band for a long distance.
The single-mode fiber has a core diameter of 10 micron, which allows single-mode beam transmission and can reduce the bandwidth and modal dispersion limitations. However, because the core diameter of a single-mode fiber is too small, it is difficult to control the beam transmission. An extremely expensive laser is required as the light source. The main limitation of single-mode optical cables is material dispersion. Single-mode optical cables mainly use lasers to obtain high-frequency bandwidth. Since LEDs emit a large number of light sources with different bandwidths, material dispersion requirements are required. Very important.
Compared with multi-mode fiber, single-mode fiber can support longer transmission distance. From 100Mbps Ethernet to 1G Gigabit network, single-mode fiber can support transmission distance of more than 5000m.
From a cost point of view, since the optical transceiver is very expensive, the cost of using single-mode fiber will be higher than that of multi-mode fiber optic cable.
Single Mode Fiber (SingleModeFiber, SMF)
Compared with multimode fiber, single-mode fiber has a much thinner core diameter, only 8-10μm. Because only one mode is transmitted, there is no inter-mode dispersion, the total dispersion is small, and the bandwidth is wide. Single-mode fiber is used in the wavelength range of 1.3～1.6μm. Through appropriate design of the refractive index distribution of the fiber, and the selection of high-purity materials to prepare a cladding 7 times larger than the core of the fiber, it can be realized simultaneously in this wavelength range. Minimum loss and minimum dispersion.
Single-mode optical fibers are used in long-distance, large-capacity optical fiber communication systems, optical fiber local area networks and various optical fiber sensors.