Single-mode and Multimode Fiber Optic Cable–Which One Is More Suitable for Your Network?

There are several main types of fiber optic cables in the market. The way they are designed and the characteristics they possess determine their application areas. Different types or specifications can lead to large functional differences in the systems, Which may have direct impact on the current and long-term performance of the network as well as the cost. Therefore, it is important for users to understand the differences among fiber optic cables.

Introduction of Single-mode and Multimode Fiber Optic Cables

Fiber optic cables can be divided into two types:

Single-mode Fiber Optic Cable

A typical single-mode fiber optic cable has a small diameter core between 8 and 10.5 µm. Since single-mode optical cable has relatively narrow core diameter, it has only one mode of transmission. With only a single wavelength of light passing through its core, single-mode fiber optic cables prevent any distortion which could result from overlapping light pulses, providing lower signal attenuation and higher transmission speeds of any fiber cable type, and creating the ability for the signal to travel further.

Multimode Fiber Optic Cable

Multimode is made of glass fiber. Its common diameter is between 50 and 100 µm. Compared with single-mode optical fiber, multimode fiber optic cable has a large core diameter, so it has multiple modes of light to run through. That is to say, several wavelengths of light can be propagated in the fiber core at the same time. However, the quality of the signal is reduced in long distance because multiple paths of light can cause signal distortion at the receiving end, resulting in an unclear and incomplete data transmission.

How Do I Know What Type of Fiber Cable I Need?

This is based on transmission distance to be covered as well as the overall budget allowed. We must have a comprehensive commanded of the differences of these two types cables, and then choose the more suitable one. Here is the detailed comparison.

Core Diameter

As noted above, we have known that single-mode core diameters are much smaller than multi-mode. The standard used in broadcasting and production of single-mode fiber is 9.5 µm, and the multimode fiber is 50 to 100 µm. A micron is one thousandth of one millimeter. 10 µm is therefore extremely small. It’s too small to see with the naked eye.

Light Sources

Multi-mode devices usually use an LED as a light source. So does multimode fiber optic cable. Single-mode optical cables often use a laser or laser diode, to produce light injected into the cable. Lasers produce light that is coherent, and its beam can be very thin. As far as we know, there are no audio or video devices that accept both single-mode and multi-mode fiber. So single-mode and multimode fiber optic cables cannot be mixed. Incompatibility between types has as much to do with the fiber type as it does with the device and the light source that generates the signal.

Bandwidth

The bandwidth of fibers is inversely proportional to the distance. That is to say, the further the signal is transmitted, the lower the bandwidth will be. For example, if the fiber has a bandwidth of 500MHz per kilometer, the bandwidth of the fiber at a distance of 1 kilometer will be 500MHz. At 2 kilometers, the bandwidth will be less than 500MHz. Multimode can support a maximum bandwidth of 4700 MHz/km (OM4 laser optimized) and will be extended to a distance of up to 2km (@100 Mbps). Currently the maximum speed supported on multimode fiber is 100Gbps. Single-mode fiber can support virtually unlimited modal bandwidth as well as Terabit data rates. It can also span up to 100km without the use of a repeater. And the bandwidth of single-mode is as much as 100,000 GHz.

Distance

The transmission distance of multimode fiber optic cable is shorter than that of single-mode optical cables. In a data center, it’s typical to use multimode which can get you 300–400 meters. If you have longer distance requirements, single-mode can get you 10km, 40km, 80km, and even farther. At the same time, the cost is also expensive.

Conclusion

To sum up, single-mode and multimode fiber optic cables have distinctive characteristics. Therefore, it’s important to find out which one is more suitable for your network. How to choose one of them and make them work well in your networks is based on the different applications and cost.