Difference Between Single-mode and Multimode Fiber

Single-mode vs Multimode Fiber

With every passing year, optical fiber seems more and more to be the future of networking. It is now being used by telecoms but is not as common in home or office networks. There are two basic types of optical fibers, single-mode and multimode. The main difference between single-mode and multimode optical fiber is the size of the core. Single mode fiber has a core that measures around 5um while the multimode fiber core measures 50um or more.

Because multimode fiber is thicker, it can accommodate more signals for greater bandwidth. So, for greater speed, it is better to use multimode fibers as a single cable is capable of handling what would otherwise require multiple single-mode cables. The downside to using a thicker core is the increased attenuation. A greater amount of attenuation means that a light signal would fade away in a shorter distance. For this reason, telecoms prefer using a single-mode fiber when they want to connect long distances. Even though bandwidth is reduced, using single-mode fibers mean that they do not have to install as many repeaters which can greatly add to the cost of the installation.

Another difference between multimode and single-mode fiber is the type of equipment you can use with them. The small size of single-mode fibers requires specialized equipment like lasers in order to focus the light beam correctly. This is not a problem if you only need a few of these very expensive pieces of equipment. However, for installations in specific locales like an office or a campus, it is better to use multimode fibers. Because of the larger core, a multimode fiber can effectively gather more light, thereby allowing the use of cheaper equipment like LEDs in lieu of lasers. It may not be as precise, but its significantly lower cost makes it a viable replacement for the copper-based networks in place today.

Single-mode and multimode optical fibers have their own area where they excel. Single-mode fibers are better for moving information across great distances and are routinely used by telecoms. In comparison, a multimode fiber is ideal for local networks due to its low cost.

Summary:

A single-mode fiber is uses a thinner core than a multimode fiber.
Multimode fibers have a greater bandwidth than single-mode fibers.
A single-mode fiber is better for longer distances than a multimode fiber.
Multimode fibers can work with cheaper equipment while single-mode fibers cannot.

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