Cleerline Technology Group

Feb. 12, 2021 - So, you're running fiber optic cable.  Great!  What are you connecting it to?  Fiber optic networking equipment used to be limited and expensive.  Now, however, prices have gone down, and options have gone up!  These days, you can find fiber-enabled routers and switches easily.  

However, there are different fiber types and configurations.  It wouldn't be feasible to build a different switch for every set-up.  To solve this problem, device manufactures frequently employ SFP ports.  SFP ports allow the installer to customize their fiber connection by choosing an SFP module specific to their needs. 

While Cleerline does not manufacture SFP modules at this time, you can view some common options at Cleerline Technology Group's e-commerce site, www.clrtec.com.

What's an SFP Module?

An SFP module is a Small Form-Factor Pluggable.  Simply put, it is a small transceiver that can send and receive data over fiber.  SFPs plug into your network switch or media converter.  They are hot-pluggable, so modules can easily be swapped in and out.  SFPs are also sometimes referred to as miniGBIC (gigabit interface converter).  At this point, SFPs have mostly replaced older and larger GBIC.  As the name indicates, SFP modules are small, accommodating only 1-2 fiber optic connectors. 

Major Considerations

Before choosing SFP modules, check your electronics for any specific requirements.  You will also need to know what transmission distance is required.  This information will help you choose both the correct fiber type and the correct SFP.

Are all SFP Modules the Same?

Short answer: no.  SFP modules are distinguished by their bandwidth capabilities, wavelength, and distance capability.

The SFP you choose must be compatible with the fiber cable you are installing.  Single mode fiber requires a single mode compatible SFP.  Multimode fiber requires a multimode compatible SFP. 

Frequently, SFPs will reference wavelength, denoting fiber type required:

• 1310/1550 nm = Single Mode (9/125 µm)
• 850/1300 nm = Multimode (50/125 µm)

Note however that 1310 nm can also work over multimode in some applications. Check the manufacturer's instructions.

Bandwidth

Most manufacturers will clearly indicate the maximum bandwidth and distance of their SFPs (i.e. 1 Gb with a maximum transmission distance of 550 meters).  However, there are a few naming conventions.  Here are some important points:

• SFP modules support up to 4.25 Gbps. 
• SFP+ modules (enhanced small form-factor pluggable) support up to 16 Gbps. 
• SFP28 modules can handle 25 Gbps over one channel. 

For higher bandwidth applications, start looking at QSP+ modules (quad small form-factor pluggable).  These modules use four channels to transfer up to 40 Gbps. 

In terms of residential installations, in most cases you will need either a SFP or SFP+ module. 

Additional Abbreviations

SFP wavelengths and distances are also indicated according to industry standards.  Some examples are noted below. Always refer to any designations made by the manufacturer of your SFP module.

Fast Ethernet (100 Mbps) = SFP

• 100BASE-SX: 850 nm (multimode) up to 550 meters
• 100BASE-FX: 1300 nm (multimode) up to 2 km
• 100BASE-LX10: 1310 nm (single mode) up to 10 km
• 100BASE-EX: 1310 nm (single mode) up to 40 km

1 Gbps = SFP

• 1000BASE-SX: 850 nm (multimode) up to 550 meters
• 1000BASE-LX10: 1310 nm (single mode) up to 10 km
• 1000BASE-EX: 1310 nm (single mode) up to 40 km

10 Gbps = SFP+

• 10GBASE-SR: 850 nm (multimode) up to 300 m
• 10GBASE-LR: 1310 nm (single mode) up to 10 km
• 10GBASE-ER: 1550 nm (single mode) up to 40 km

Again, most manufacturers will provide their distance and wavelength information directly.  Always make sure to check your SFP meets your installation's requirements. 

Connectors

SFPs are, by definition, small.  As a result, the vast majority (but not all!) SFP modules accept 2 LC connectors.  As with the rest of the system, your connectors need to match your fiber type.  A single mode SFP will only work with single mode connectors on single mode fiber, for instance.

Compatibility

There are many different SFP manufacturers.  Do you always need an OEM SFP?  Frequently, no. SFP manufacturers will often state compatibility with major brands.  They may also reference MSA standards, or Multi-Source Agreement standards.  These standards help ensure cross-brand functionality. 

As a rule of thumb, if considering an SFP from a third-party manufacturer, do make sure to check compatibility before purchasing. 

SFP modules allow a great deal of flexibility, but the number of options can be confusing.  Remember, always check the following:

• Device requirements
• Distance requirements
• Fiber type and wavelength (1310/1550 nm = single mode.  850/1300 nm = multimode)
• Brand compatibility

This basic information will set you on a path to a successful network installation.