Tag Archives: SFP slot

SFP Slot Definition and Its User Guideline

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It is obvious that optical transceiver is widely used in telecommunication and data center. Speaking of this, SFP module is inevitably involved. However, have you ever heard of SFP and SFP slot? Do you have any idea about how to use SFP slots? If not, read through this post to find what SFP slot is and how to use it.

What Is SFP Slot?

What is SFP port/slot? To figure this out, you must know what SFP is in the first place.

SFP, an acronym of small form-factor pluggable, is a compact and hot-pluggable transceiver used for both telecommunication and data communication applications. It connects motherboards of network devices (such as switches and routers) with optical or copper cables. By doing this, it converts Gigabit electrical signals into optical signals, and vice versa.

Therefore, just as its name implies, SFP slot is designed for use with SFP transceivers or modules. It offers a place where a SFP transceiver can plug into and then support fiber connection or copper cable connection. Different connection can support different transmission speed and distance. Normally, a Gigabit SFP inserted into a SFP port can reach a speed of up to 1 Gbps!

what is sfp slot

How to Use the SFP Slot?

SFP slot is also known as SFP port. Thus, this question can be referred to as how to use SFPs with SFP ports. SFP and SFP port usually work in pairs. That is to say, you should use SFP slot with a corresponding SFP. Normally, optical transceivers used in SFP slots can be divided into optical and copper SFPs. They can be used on a wide variety of products and intermixed in combinations of 1000BASE-T, 1000BASE-SX, 1000BASE-LX/LH, 1000BASE-EX, 1000BASE-ZX, or 1000BASE-BX10-D/U on a port-by-port basis.

The common match for SFP ports are copper SFP module applied with network cable and fiber SFP module applied with fiber optic cable. Network cable or copper cable includes Cat5e, Cat6, Cat6a, etc. While, fiber optic cable includes single mode fiber and multimode fiber. Therefore, if you want to know how to use SFP slot, you need to know how to choose right copper SFP modules or fiber SFP modules for SFP slots. As for how to choose the right SFP modules, go ahead for more details in the next two paragraphs.

Copper SFP module for SFP Slot

A copper SFP module inserted into a SFP port has a RJ45 connector. It can transmit data within 100m over copper twisted pair cable. And the data transmission rate can reach up to 1000 Mbps. It is normally divided into two types, 1000BASE-T and 1000BASE-TX copper SFP. The former uses the IEEE 802.3ab standard using four bidirectional copper pairs, and each pair supports a data rate of 250 Mbps. While, the latter uses the TIA/EIA-854 standard using two unidirectional copper pairs (one pair for transmitting, one for receiving), each of which supports a data rate of 500 Mbps.

Fiber SFP module for SFP Slot

A fiber SFP module inserted into a SFP port has a LC duplex interface. It consists of seven types, namely 1000BASE-SX, 1000BASE-LX, 1000BASE-LX10, 1000BASE-LX/LH, 1000BASE-LH, 1000BASE-EX and 1000BASE-ZX. They are used under different circumstances shown in the picture below:

sfp-ports-with-fiber-sfp-modules

Conclusion

From all the above, you may have a general understanding of what a SFP slot is and how to use it properly. SFP ports are found in Ethernet switches, routers, firewalls and network interface cards, etc. If you want to transfer data in 100m, then either a copper SFP or fiber SFP is a right choice to match the SFP port. If you want to transfer data over 100m, then a fiber SFP is needed.

Related articles:

Can I Connect Fiber Optic Transceivers of Different Brand?

Understanding Combo SFP Port on Ethernet Switch

Gigabit Slots: SFP Port vs. RJ45 Port vs. GBIC Port

In Gigabit Ethernet applications, either SFP port, RJ45 port or GBIC port is used in different Gigabit devices, such as switches, routers, servers and storages. And some latest wireless access points (APs) are also equipped with SFP port. Since all these three port types only support 1Gbit and do not go any higher, why are they created instead of using only one type?

RJ45 port and SFP port in an Ethernet switch

SFP Port vs. GBIC Port: An Improvement in Dimension

SFP port and GBIC port can be found in a variety of equipment, including Ethernet switches, routers, network interface cards, servers, etc. Today most Ethernet switches are designed with as least one or two Gigabit SFP uplink slots. What is SFP port? As the name implies, SFP port is intended for taking in SFP (mini-GBIC) fiber modules with small form-factor (SFF) connectors, while GBIC port is for accepting GBIC modules.

GBIC module and SFP module

The two types of ports can provide the same data rates and same distances in Gigabit applications, but the same number of SFP ports uses less space than that of GBIC ports. Since they have the equal functionality, SFP has gradually taken the place of the older GBIC in Gigabit networking for space-saving and economical reasons. The table below is a comparison of SFP port vs. GBIC port.

Parameter SFP Port GBIC Port
Supported Optical Modules SFP transceiver (single-mode/multimode, simple/duplex, CWDM/DWDM) GBIC transceiver (single-mode/multimode, simple/duplex, CWDM/DWDM)
Transceiver Receptacle Type LC, RJ45 SC, RJ45
Supported Standards 1000BASE-T, 1000BASE-SX, 1000BASE-LX, 1000BASE-LX10, 1000BASE-LX/LH, 1000BASE-LH, 1000BASE-EX, 1000BASE-ZX, 1000BASE-BX, 1000BASE-CWDM, 1000BASE-DWDM.
Supported Distances Up to 100 m, 300 m, 2 km, 10 km, 20 km, 40 km, 80 km, 100 km, 150 km.
Module DOM Function Modules support digital optical monitoring (DOM) function, providing real-time monitoring of transceiver’s operation temperature, optical input, optical output, laser bias current and supply voltage.

If you want to know more about the SFP types that the SFP port support and their detailed specifications, such as wavelengths and distances, you can read: How Many Types of SFP Transceivers Do You Know.

SFP vs. RJ45 port: Distance Makes Difference

The RJ45 ports in Gigabit networking devices follow the 1000BASE-T Ethernet standard. They only support twisted pairs for network connections, and the distance is limited to 100 m (330 feet). RJ45 port uses Category 5/5e/6 and higher level copper Ethernet cables for 1Gbit transmission. Compared with switch using only RJ45 port, SFP port switch supports more types of communication cables and longer reaches of links. Here are the differences between SFP vs. RJ45 port.

Parameter SFP Port RJ45 Port
Connection Cable Types Multimode fiber cable, single-mode fiber cable, twisted pairs (Cat5, Cat6 or higher). Twisted pairs (Cat5, Cat6 or higher).
Max. Transmission Distance MMF (550 m), SMF (150 km), Cat5 (100 m) 100 m (330 ft)
Data Rate 1000 Mbps (1G) 1000 Mbps (1G)

Since most end-points at the customer’s are still using RJ45 port, in order to retaining the convenience of RJ45 port while providing the advantage of SFP network to customers, some switches include combo SFP/RJ45 ports. So users can choose to utilize either the SFP port or the RJ45 port at a time for short-distance connections.

What Is Dual-Rate SFP Port?

Unlike the combo SFP/RJ45 port which is actually a link shared by two different ports, a dual-rate SFP port is one single SFP slot that can be configured to support two different data rates. Generally a dual-rate SFP slot can set to be either 1G mode or 10G mode, i.e., an SFP module or an SFP+ module can be installed in it. But the actual data rate of the transmission depends on the mode being settled and the transceiver module being used. There are several cases:

  • The dual-rate SFP slot is 10G activated, and an SFP+ module is installed; the interface is in 10G mode.
  • The port is 10G activated, but an SFP module is installed; the interface is in 1G mode.
  • The port is not 10G activated, but an SFP+ module is installed; the interface will be link down state.
  • The port is not 10G activated, and an SFP module is installed; the interface is in 1G mode.

Summary

The three port types—SFP port, RJ45 port and GBIC port—are used in different networking equipment. The SFP port is now more commonly used than GBIC port since the former one provides the same function and is more compact. When SFP port vs. RJ45 port, SFP port supports connectivity through varieties of fiber cables and the copper twisted pairs, and a wide range of link distances, but RJ45 port accepts only twisted pair cables and a shorter distance. Since every thing has both two sides, it is not always the best to choose SFP slot. The two articles: GBIC vs SFP: When It’s Best to Use GBIC and When to Use SFP, and RJ45 vs SFP: Which Should I Use to Connect Two Switches, specifically discussed when to use which port/module type.