When optical fiber is required for monitoring generic cabling, at least we should understand what optical fiber is and how to distinguish single-mode and multi-mode. We try to use popular words in this article to let novices understand. In fact, every professional book has the knowledge of optical fiber, but it seems that there is not much to remember after reading, because it is too professional and too remote for most non professional people.

A section explaining the single-mode optical fiber is intercepted for you to see: "When the geometric size of the optical fiber is mainly that the core diameter can be close to the optical wavelength, such as when the core diameter D1 is in the range of 5 to 10 µ m, the optical fiber only allows the basic mode HE11 to propagate in it, and all the other higher modes are cut off. Such optical fiber is called single-mode optical fiber."

Optical fiber is a communication line that transmits optical signals. Kao Kun, former president of the Chinese University of Hong Kong, and a foreign scientist who did not remember his name first proposed that optical fiber could be used to transmit communications, for which he 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 the project. The fiber core of an optical fiber is very thin, which is a kind of glass fiber about the thickness of a hair.

The advantage of optical fiber is that it transmits signals through light guide, which is non-conductive and not afraid of lightning, so it does not need grounding protection.

According to the transmission mode of light in optical fiber, we can divide it into multimode optical fiber and single-mode optical fiber. For our users, you can remember the names of multimode and singlemode.

Multimode fiber: It can transmit light of various modes.

Single mode fiber: Only one mode of light can be transmitted.

The middle core of multimode optical fiber is thicker and the middle core of single-mode optical fiber is thinner, but the multimode optical fiber is 50 μ m and the single-mode optical fiber is 10 μ m. If you forget the unit conversion of micrometers, 1 mm=1000 micrometers. The transmission distance of multimode optical fiber is relatively short, generally only a few thousand meters. The transmission distance of single-mode optical fiber is much longer, usually dozens of times that of multimode optical fiber. Single mode fiber is generally more expensive than multimode fiber. The outer sheath of single-mode optical fiber is generally yellow. The color of multimode optical fiber is generally orange.

The advantages of using optical fiber also include:

1. If copper cable is selected when the transmission distance of information point is greater than 100m. Repeaters must be added or network equipment and weak current room must be added to increase the cost and hidden trouble. The use of optical fiber can easily solve this problem.

2. There are a large number of electromagnetic interference sources in specific working environments (such as factories, hospitals, air-conditioning rooms, power rooms, etc.). Optical fibers can operate stably in these environments without electromagnetic interference.

3. There is no electromagnetic leakage in optical fiber, so it is very difficult to detect the signal transmitted in optical fiber. It is a good choice in places with high confidentiality requirements (such as military, R&D, audit, government and other industries).

4. In an environment with a high demand for bandwidth, which is more than 1G, optical fiber is a good choice.

In practical application, if the distance is far, single-mode fiber is used; If the distance is close, multimode optical fibers can be used. In addition, optical fiber transceivers are required for optical fiber transmission. Single mode optical fibers use single-mode transceivers, and multimode optical fibers use corresponding multimode transceivers. The price of single-mode optical fibers is higher than that of multimode optical fibers.