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The Difference Between Single-Mode Fiber and Multimode Fiber

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When building a fiber optic network, one of the first decisions you’d need to make is whether to go with multimode fiber or single-mode fiber. In order to make the best choice, you need to understand what these fiber modes are and how they differ from each other. This will come in handy when you study for your CompTIA A+ practice test and the actual exam.

What Is Single-Mode Fiber?

This basically has a small core size that can allow only one ray of light or mode, usually 1310 nm to 1550 nm, to be sent. Due to this, there’s less light reflection produced when light passes through it. In turn, this decreases fiber attenuation and allows signals to be transmitted farther. This is why single-mode fiber is perfect for long-distance applications requiring higher bandwidth.

What Is Multimode Fiber?

This contains bigger cores to effectively guide multiple modes simultaneously so that data can pass through them. This action produces higher attenuation rates and dispersion, as well as light reflections, which in turn reduces signal quality over long distances. This is why multimode fiber is more ideal for applications that don’t need significant bandwidth such as data, video, and audio applications.

General Differences Between Single-Mode Fiber and Multimode Fiber

The following differences are a result from the difference in their internal structures:

  • Difference in Optics – Multimode fiber is typically utilized with      LED-based fiber optics for transmissions within short distances,      while single-mode fiber must be utilized with laser diode-based fiber optics for more accurate calibration needed for injecting light into fiber optic cables. Additionally, connectors that single-mode fiber uses have more stringent requirements for alignment than those used by multimode fiber.
  • Difference in Light Propagation – Single-mode fiber has only one kind of light propagation, the step index, while multimode fiber has two kinds, the graded index and step index. Light propagation decreases less in transmissions using single-mode fiber than in those using multimode fiber.
  • Difference in Cost of Deployment – Generally speaking, while the cost of a single-mode fiber cable is lower than that of a multimode fiber cable, the cost of deployment for single-mode fiber systems are more costly. The reason for this is that it’s the actual optics that influence the overall cost of network systems. Multimode transceivers require less power.

Multimode Fiber or Single-Mode Fiber?

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When choosing between multimode fiber and single-mode fiber, the main thing you need to take into account is your specific distance requirement. For example, within a typical data center, you can utilize multimode fiber that can give you between 300 and 400 m. However, if you need longer runs and connection over significantly longer distances, single-mode fiber can provide you with 10 to 80 km or farther. You just have to utilize the proper optics for the required distance.

Put simply, single-mode fiber is appropriate for distances that exceed 500 m, while multimode fiber is appropriate and more cost-effective for distances up to 550 m. Aside from the transmission distance, you should consider the overall cost of deployment.