What is the Difference Between Single Mode Fiber and Multimode Fiber?
What is the Difference Between Single Mode Fiber and Multimode Fiber?
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Optical fiber generally divided into three layers: core, cladding and coating. The core and cladding composed of glass with different refractive indices. The fiber core is a glass with a high refractive index (silicon dioxide doped with germanium). And the fiber cladding is a silica glass with a low refractive index (pure silica). Light enters the optical fiber at a specific incident angle. And complete emission occurs between the optical fiber and the cladding. Because the refractive index of the cladding is slightly lower than that of the core. So that it can propagate in the optical fiber. The main function of the coating is to protect the optical fiber from external damage while increasing the flexibility of the optical fiber. As mentioned earlier, the core and cladding made of glass. Which cannot be bent and is fragile. The use of coating protects and extends the life of the optical fiber.What is the different between single mode fiber and multimode fiber?
An outer sheath added to the non-bare fiber. In addition to protecting it, the outer sheath of different colors can also used to distinguish various optical fibers.
According to the transmission mode, optical fiber can divided into single-mode fiber and multi-mode fiber. Light enters the optical fiber at a specific incident angle. And complete emission occurs between the optical fiber and the cladding. When the diameter is small. Only one direction of light allowed to pass. Which is a single-mode fiber. When the diameter of the optical fiber is large. It can allow light to enter and propagate at multiple incident angles. At this point, it called multimode optical fiber.
What are the characteristics of optical fiber?
Optical fiber has two main transmission characteristics: loss and dispersion. The loss of optical fiber refers to the attenuation of the optical fiber per unit length, measured in dB/km. The level of optical fiber loss directly affects the transmission distance of the optical fiber communication system or the distance between relay stations. Optical fiber dispersion refers to the signal transmitted by the optical fiber carried by different frequency components and different mode components. And the transmission speeds of different frequency components and different mode components are different, resulting in signal distortion.
Optical fiber dispersion divided into material dispersion, waveguide dispersion, and modal dispersion. The first two dispersions caused by the signal not being a single frequency. And the latter dispersion caused by the signal not being a single mode. The signal not being a single mode will cause mode dispersion. Single-mode optical fiber has only one fundamental mode. So there is only material dispersion and waveguide dispersion, but no modal dispersion. Multimode optical fiber has inter-modal dispersion. The dispersion of optical fiber not only affects the transmission capacity of the optical fiber. But also limits the relay distance of the optical fiber communication system.
What is single mode fiber?
What is multimode fiber?
Multimode fiber is a type of optical fiber that allows multi-mode transmission. The core diameter of a multimode fiber is usually 50 μm/62.5 μm. Since the core diameter of a multimode fiber is relatively large. It can allow different modes of light to be transmitted on one optical fiber. The standard wavelengths of multimode are 850nm and 1300nm respectively. There is also a new multimode fiber standard called WBMMF (Wideband Multimode Fiber). Which uses wavelengths between 850nm and 953nm. Both single-mode fiber and multimode fiber have a cladding diameter of 125 microns.
What is the difference between single mode fiber and multimode fiber?
1.Transmission distance of optical fiber
The smaller diameter of single mode optical fiber makes the reflections tighter.Which allowing only one mode of light to propagate, allowing the optical signal to propagate farther. When light passes through the core, the amount of light reflection is reduced. Which reduces attenuation and causes further signal propagation. Since there is no intermodal dispersion or the intermodal dispersion is small. Single mode fiber can transmit 40 kilometers or more without affecting the signal. Therefore, single-mode optical fiber generally used for long-distance data transmission, telecommunications companies, cable TV providers, and universities, etc.
Multimode optical fiber has a larger diameter core and can transmit light in multiple modes. In multimode transmission, due to the larger core size, the intermodal dispersion is larger. That is, the optical signal “spreads” faster. The signal quality will be reduced when transmitted over long distances. So multimode optical fiber is generally used for short distances, audio/video applications, and local area networks (LANs). And OM3/OM4/OM5 multimode optical fibers can support high-speed data transmission.
2.Bandwidth and capacity of optical fiber
Bandwidth defined as the ability to carry information. The main factors affecting the bandwidth of optical fiber transmission are various dispersions. Among which modal dispersion is the most important. Single-mode fiber has less dispersion. So it can transmit wide-bandwidth light over long distances. Because multimode fiber will produce complex problems. Such as interference, it is not as good as single-mode fiber in bandwidth and capacity. The bandwidth of the latest generation of multimode fiber OM5 set at 28000mhz/km. While the bandwidth of single-mode fiber is much larger.
3.Fiber Cost
If single-mode fiber has higher bandwidth and longer transmission distance. Why do we need multimode fiber? Cost may be the key to this question. Since the core diameter of single-mode fiber is too small. It is difficult to control light transmission. So laser is needed as the light source. Since optical transmitters and receivers are very expensive, the cost of using single-mode fiber will be higher than multimode fiber. This fact has prompted most data centers to use multimode fiber to save costs.
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