Multimode optical fiber is the most original technology of optical fiber communication, which is a revolutionary breakthrough for human beings to realize communication through optical fiber for the first time. Later, with the development of optical fiber communication technology, especially the development of laser technology and people's urgent need for long distance and large amount of information, people have found a better optical fiber communication technology single mode fiber communication. Next, ETU-LINK will introduce single-mode fiber and multimode fiber and their differences.

Multimode optical fiber

Multimode fiber is another common type of optical fiber. The core diameter is 50 μm-100 μm, and the working wavelength is 850nm or 1310nm. It is relatively easy to couple with optical devices. It can transmit multiple modes at a given wavelength.

Compared with twisted pair, multimode fiber can support longer transmission distance. The core diameters of common multimode fibers are 50 μm and 62.5 μm.

As there are hundreds of modes transmitted in multimode fiber, the propagation constant and group rate of each mode are different, which makes the band width of the fiber narrow, the dispersion is large, and the loss is large, which limits the frequency of digital signal transmission. Therefore, it is only suitable for medium short distance and small capacity optical fiber communication system, so it can only transmit several hundred meters.

Single mode fiber

Single mode fiber has only one glass fiber (two in most applications), and the core diameter is 8.3 μ m ~ 10 μ M. Due to the relatively narrow core diameter, single-mode fiber can only transmit optical signals with wavelength of 1310nm or 1550nm, so it is relatively difficult to couple with optical devices. The bandwidth of single-mode fiber is higher than that of multimode fiber, but at the same time, it also puts forward higher requirements for the spectral width and stability of the light source: the spectral width should be narrow, and the stability should be good.

The single-mode optical fiber uses the extremely expensive laser as the light source, has small dispersion and small core diameter, and only transmits one mode of light, so it can realize large capacity and long-distance transmission.

Difference between single mode fiber and multimode fiber

1. Single mode fiber supports single fiber transceiver, while multimode fiber only supports dual fiber transceiver;

2. The core diameter of single-mode fiber is small, only one mode transmission is allowed, and the dispersion is small. The working wavelengths are 1310nm and 1550nm, so it is relatively difficult to couple with optical devices; the core diameter of multimode fiber is 62.5/125 μm or 50 / 125 μm, allowing hundreds of mode transmission, with large dispersion, and working wavelength of 850nm or 1310nm. The coupling with optical devices is relatively easy;

3. The identification of multi-mode is "MMF", and that of single-mode is "SMF";

4. Single mode is to use laser as light source, and multimode is to use LED as light source.

Finally, ETU-LINK will teach you how to choose the type of optical fiber. Multimode fiber can be selected for short-distance transmission, and single-mode fiber can be used for long-distance transmission.