What is the difference between single mode fiber and multimode fiber? Can single mode and multimode be mixed?

What is the difference between single mode fiber and multimode fiber? Can single mode and multimode be mixed?

Single-mode fiber and multimode fiber are two kinds of optical fibers mainly used for transmitting optical signals. They differ significantly in transmission characteristics, transmission distance, and transmission bandwidth. This article will detail the differences between single-mode and multimode fibers and explain their limitations in practical applications.

First, let's understand single mode fiber. The core diameter of a single mode fiber is very small, usually only 9/125 microns. Because the core diameter is so small, single-mode fibers can only transmit a single beam of light, and even if the optical signal is transmitted over long distances, no interference between modes occurs. This allows single mode fiber to achieve high bandwidth and long distance transmission. Single-mode fiber is suitable for applications requiring high-speed data transmission and high-capacity transmission, such as long-distance transmission, satellite communications and Internet backbone networks.

In contrast, multimode fiber has a larger core diameter, typically 50 or 62.5 microns, which allows it to transmit multiple beams of light. Multimode fiber has a relatively short transmission distance and suffers from inter-mode interference. When an optical signal undergoes multiple reflections during transmission, it causes different modes of light to travel at different speeds, resulting in signal distortion and attenuation. Due to these limitations, multimode optical fiber has a relatively short transmission distance and is generally suitable for local area networks (LAN) and short-distance communications.

In practice, single-mode and multimode fibers cannot be mixed, mainly because of their different transmission characteristics and working principles.

First of all, single-mode fiber and multi-mode fiber have different transmission modes. Due to the different structures of optical fibers, single-mode fibers can only transmit one beam of light, while multimode fibers can transmit multiple beams of light at the same time. If they are mixed, it will lead to mutual interference and distortion of optical signals.

Second, the transmission distance of single-mode fiber and multi-mode fiber is different. Single-mode optical fiber can achieve long-distance transmission, can reach tens or even hundreds of kilometers of transmission distance. The transmission distance of multi-mode fiber is relatively short, generally not more than a few kilometers.

In addition, there is a difference in the transmission bandwidth between single-mode fiber and multimode fiber. Since single-mode fiber can only transmit a single beam of light, its transmission bandwidth is higher and can reach hundreds of Gbps or even higher. On the other hand, the transmission bandwidth of multi-mode fiber is relatively low, generally between tens of Mbps and hundreds of Mbps.

It is important to note that despite the superior transmission characteristics of single-mode fibers, they are more expensive to manufacture, so in practice, multimode fibers still have a market, especially for short-distance communications and local area networks.

In summary, there are obvious differences between single-mode fiber and multimode fiber in terms of transmission characteristics, transmission distance and transmission bandwidth. Although they cannot be mixed, in different application scenarios, single-mode fiber and multimode fiber have their unique advantages and limitations. Therefore, when choosing a fiber optic transmission solution, a reasonable choice should be made according to the specific application requirements.