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The Difference Between Single mode and Multi-mode SFP’s?

SFP transceiver modules, also known as small form-factor pluggable, are hot pluggable optical transceiver modules which are commonly used for both telecommunication and data communications applications. SFP’s compact, hot-pluggable transceiver used for data communication applications.  These small metal devices plug into a special switch slot and support transfer over either fibre optic or copper networking cable.

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There are both multi-mode and single mode SFP transceiver types. Single mode SFP and Multi-mode SFP mean the SFP transceivers will work on different types of optical fibres; as in a Single mode SFP will work with Single mode fibre only, and a Multi-mode SFP will work with Multi-mode fibre only.

So, what’s the different between them? And what should we notice when using them?

Single mode SFP

Single mode fibre has much tighter tolerances for optics used. The core is smaller and the laser wavelength is narrower. This means that SMF has the capability to carry a higher bandwidth at much longer transmission distances. Single mode SFPs work mainly in the 1310nm and 1550nm wavelengths and is mostly used in a long distances transmission environment reaching 2km, 10km, 40km, 60km, 80km and 120km.

Multi-mode SFP
Multi-mode fibre uses a much bigger core and usually uses a longer wavelength of light. Because of this, the optics used in Multi-mode have a higher capability to gather light from the laser. In practical terms, this means the optics are cheaper. The common Multi-mode SFPs work in 850nm wavelength and is only used for short distance transmission reaching 100m and 500m. Though it’s not able to transport for long distance, it can transport many kinds of optical signals.

Single mode vs Multi-mode differences

Working Wavelength: Single mode SFP module have a narrower laser wavelength, which works mainly in 1310nm and 1550nm wavelength. Whereas Multi-mode SFP module works in 850nm wavelength due to the larger core size.

Cost: When comparing Single mode SFP vs Multi-mode SFP in terms of cost, single mode SFP is more expensive than Multi-mode SFP. The cost difference between single mode SFP and Multi-mode SFP mainly arises from the different transmitters they use. The transmitter of single mode SFP are more costly than that of Multi-mode SFP. Hence, Multi-mode SFP module is cheaper.

Transmitter: Single mode SFP and Multi-mode SFP’s use different types of transmitters. VCSELs are typically used in Multi-mode SFP transceivers. They can be tested on the wafer level and don’t need a hermetic package. They have complex layer structures and often require a hermetic package to achieve higher emission power and stable single mode operation. Therefore, Edge-emitting lasers are more costly than VCSELs.

Typically single mode SFP are more suited for long-reach data transmission applications while Multi-mode SFP is generally utilized for short transmission distance. Which to choose depends on the actual needs.