Differences Between MMF and SMF Optic Cables

Keith AndrewsPresident
Both MMF (multi-mode fiber) and SMF (single-mode fiber) are types of optical fiber that can aid in communication applications. These thin strands of silica or glass will allow communication to occur between devices. The transmission of light between each end of the fiber is what enables communication to occur. Most designers prefer fiber optics because transmission can occur over long distances and can transmit at high data rates. The distance the signals can travel is up to 100 km and up to 100 Gbit/s with not as much loss. Fiber optic is preferred because there is less of a signal loss, and it is less affected by electromagnetic interference. Here are some of the major differences between MMF and SMF.

1. Number of Light Beams
SMF (single-mode fiber) carries a single beam of light and an MMF (multi-mode fiber) carry multiple beams of light. MMF has a larger core than SMF because it has to support the multiple beams of life. This yields different optical properties within the core. The light traveling through the center will move at a rate that is slower than other modes.

2. Pulse Fidelity 
SMF is more likely to retain the fidelity of each pulse over longer distances than MMF. This is because of the shorter core. This is an important consideration if you are planning a project. Pulse fidelity should be carefully considered to avoid delays in communication that may occur otherwise.

3. Cost Considerations
There are numerous cost considerations to review before deciding if MMF or SMF is better for your application. In general, designers with budgetary constraints are more likely to select MMF over SMF. Even equipment used for MMF is less expensive than SMF.

4. MMF and SMF Color Distinction
In most designs, a color distinction is made between the two types of wires. SMF cables are usually distinguished by a yellow sheath. Aqua or orange is typically used for MMF cables. Any angular physical connectors may be displayed in a green color. Identification is easier with color coding.

The Primary Differences MMF and SMF Optic Cables
SMF optic cables are known for greater MMF bandwidth distances. It can support more than one propagation mode. With SMF optic cables, it has modal dispersion limitations. Only a single wavelength is required for SMF fiber optics. As mentioned, costs can be reduced by using MMF, but with larger core sizes also mean that designers can create a lower cost electronic device.

Keep in mind that signal integrity is easier to maintain over longer distances with SMF. SMF is preferred for this reason over MMF. It has a smaller core and light can move through the core at much faster rates than MMF.

When you are considering purchasing these devices, review the ISO 14000 and ISO 9001 protocols. Every brand has a different rating. It's best to find the brand that will work best for your application. Talk to a professional or read reviews to find the best protocol, core size, and wavelength for what you need.

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