Single-mode Fiber vs. Multimode Fiber: Which to Choose?

With bandwidth demand increasing in enterprise and data center networks, the system designers may believe that single-mode fiber enjoys an increasing advantage over multimode fiber in premises applications. But higher Ethernet speeds do not automatically mean that single-mode fiber is the right choice even though it holds advantages in terms of bandwidth and reach for longer distances. Multimode fiber can easily support most distance requirements in enterprise and data center networks, and it is a more cost-effective choice over single-mode fiber for the shorter reach applications. So single-mode fiber and multimode fiber, which one to choose?

Differences Between Single-mode Fiber and Multimode Fiber

 

 

At the very first beginning, let’s make clear the differences between single-mode fiber and multimode fiber. Generally, single-mode fibers have a small core size (<10 µm) that permits only one mode or ray of light to be transmitted. This tiny core requires precision alignment to inject light from the transceiver into the core, significantly driving up transceiver costs. By comparison, multimode fibers have larger cores (62.5 µm or 50 µm) that guide many modes simultaneously. The larger core makes it much easier to capture light from a transceiver, allowing source costs to be controlled.

Similarly, multimode connectors cost less than single-mode connectors as a result of the more stringent alignment requirements of single-mode fiber. Single-mode connections require greater care and skill to terminate, which is why components are often pre-terminated at the factory. On the other hand, multimode connections can be easily performed in the field, offering installation flexibility, cost savings and peace of mind.

The light propagation between single-mode fiber and multimode fiber is totally different. Multimode fiber has two types of light propagation—step index and graded index, while single-mode fiber has only one step index. And the light propagation reduces less in the single-mode fiber’s transmissions than that of multimode fiber.

The following table shows the main differences between single-mode fiber and multimode fiber.

 

 

How to Choose One Over the Other?

 

 

Choosing the single-mode fiber or multimode fiber is based on your transmission distance need and the overall budget allowed. Single-mode fiber is normally used for long distance transmissions with laser diode based fiber optic transmission equipment, while multimode fiber is usually used for short distance transmissions with LED based fiber optic equipment. If the distance is less than a couple of miles, multimode fiber will work well. And the transmission costs, including both transmitter and receiver sides, will be in the range of $ 500 to $ 800. If the distance to be covered is more than 3-5 miles, single-mode fiber is the choice. And the transmission systems designed for use with single-mode fiber will typically cost more than $ 1000 due to increased cost of the laser diode.

Conclusion

 

 

Generally, multimode fiber is more cost-effective choice for data center applications up to 550 meters. Single-mode fiber is best used for distances exceeding 550 meters. Besides the transmission distance, the overall cost should also be taken into consideration. Whether single-mode fiber or multimode fiber, choosing the one that best suits your network is the smartest choice.

 Originally published: www.fiberopticshare.com