When monitoring integrated wiring needs to use optical fiber, at least we should understand what is optical fiber and how to distinguish between single-mode and multi-mode. In this article, we try to use popular text to make it clear to novices. In fact, every professional book has the knowledge of optical fiber, but it seems that there is not much that can be remembered after reading it, because it is still too professional and uncommon for most non-professionals.
Cut out a paragraph explaining single-mode fiber for everyone to see: "When the geometric size of the fiber, mainly the core diameter can be similar to the wavelength of light, such as the core diameter D1 in the range of 5-10µm, the fiber only allows the fundamental mode HE11 to propagate in it , and the rest of the higher-order modes are all cut off, and such a fiber is called a single-mode fiber."
Optical fiber is a communication line that transmits optical signals. Kao Kun, the former president of the Chinese University of Hong Kong, and a foreign scientist who can't remember the name first proposed that optical fibers could be used to transmit communication, for which Kao won the 2009 Nobel Prize in Physics.
Usually, a certain number of optical fibers are combined into optical cables in a certain way for use in projects. The core of an optical fiber is very thin, a glass filament about the thickness of a human hair.
The advantage of optical fiber is that it transmits signals through light guide, is not conductive, and is not afraid of lightning strikes, so it does not need grounding protection.
According to the transmission mode of light in the fiber, it is divided into: multi-mode fiber and single-mode fiber. For our users, you can remember the origin of the multimode and singlemode names.
Multimode fiber: can transmit multiple modes of light.
Single-mode fiber: Only one mode of light can be transmitted. 
The middle core of multi-mode fiber is thicker, and the middle core of single-mode fiber is thinner, but the two are relatively speaking, the multi-mode fiber is 50 microns, and the single-mode fiber is 10 microns. If you forget the unit conversion of microns, 1 mm = 1000 microns. The distance of multimode fiber transmission is relatively short, generally only a few kilometers. The transmission distance of single-mode fiber is much farther, usually several tens of times that of multi-mode fiber. The price of single-mode fiber is generally more expensive than that of multi-mode fiber. The color of the outer sheath of the single-mode fiber is generally yellow. The outer color of multimode fiber is generally orange-red.
The advantages of using fiber optics also include:
1. When the information point transmission distance is greater than 100m, if you choose to use copper cable. It is necessary to add repeaters or add network equipment and weak current rooms, thereby increasing costs and hidden troubles, which can be easily solved by using optical fibers.
2. There are a large number of electromagnetic interference sources in specific working environments (such as factories, hospitals, air-conditioning computer rooms, power computer rooms, etc.), and optical fibers can be immune to electromagnetic interference and operate stably in these environments.
3. There is no electromagnetic leakage in the optical fiber, and it is very difficult to detect the signal transmitted in the optical fiber. It is a good choice in places with high confidentiality requirements (such as military, R&D, auditing, government and other industries).
4. In environments with high demand for bandwidth, reaching more than 1G, optical fiber is a good choice.
In the actual application process, if the distance is long, single-mode fiber is used; if the distance is short, multi-mode fiber can be used. In addition, fiber-optic transmission requires the use of fiber-optic transceivers. Single-mode fiber uses single-mode transceiver, and multi-mode fiber uses corresponding multi-mode fiber. Mode transceivers, the price of single-mode fiber transceivers is higher than that of multi-mode transceivers.