What are the SFP ports on Gigabit switches used for? What's the effect?

- Oct 27, 2020-

What is SFP optical module?

SFP optical module is an interface device that converts gigabit electrical signals into optical signals. It is an industry-standard small and pluggable gigabit optical transceiver module that can be plugged into network equipment such as switches, routers, and media converters. The SFP port is used to connect optical or copper network cables for data transmission. Usually we can find it in Ethernet switches, routers, firewalls and network interface cards.

What is an SFP port?


The main function of the SFP port is for signal conversion and data transmission. Its port complies with the IEEE 802.3ab standard (such as 1000BASE-T), and the maximum transmission distance can reach 1000 Mbps (the SFP port of the switch supports 100/1000Mbps).

SFP port features

The SFP port is a hot-swappable I/O interface (referring to input/output interface), which has strong flexibility and is suitable for a variety of products, such as 1000BASE-SX, 1000BASE-LX/LH, 1000BASE-ZX or 1000BASE -BX10-D/U ports can be exchanged, and the SFP port is backward compatible, supporting 10/100/1000Mbps.

SFP port of Gigabit switch

The SFP port of the gigabit switch can be used to expand the switching function of the entire network by connecting various types of optical fibers (such as single-mode and multi-mode fiber) and network jumpers (such as Cat5e and Cat6), but the SFP port of the gigabit switch The SFP optical module must be inserted before use, and then use fiber jumpers and network jumpers for data transmission. All enterprise-level switches on the market now have at least two SFP ports, which can be used to construct ring or star network topologies between different buildings, floors or areas through the connection of optical fibers and network jumpers.


Advantages of SFP optical module

The volume of the SFP optical module is reduced by half compared with the volume of the GBIC optical module. The number of SFP ports on the same panel will be twice that of the GBIC optical module. The same SFP optical module has a plug-and-play mini optical fiber slot, which conforms to the data With high-density requirements in the center, SFP optical modules will replace GBIC optical modules in data centers in the future.

Popular SFP optical modules

Because the SFP optical modules of GLC-BX-D and GLC-BX-U are powerful and highly sought after, these two types of optical modules support data optical monitoring, allowing users to monitor the performance of optical modules in real time, such as tracking temperature, light Output power, optical input power, laser bias current, transceiver power supply voltage, etc.

In addition, the 1000BASE-BX10-D SFP optical module with a transmission distance of 10km, the GLC-BX40-D SFP optical module with a transmission distance of 40km, and the GLC-BX80-D SFP optical module with a transmission distance of 80km are also popular among users.

The above SFP optical modules have the following four advantages:

1. Supports hot swap, which can reduce installation, maintenance and management time;

2. The port is flexible;

3. Robust design enhances reliability;

4. Support digital optical monitoring (DOM) function.

SFP optical module application

1. Short-distance network wiring

1000BASE-T SFP optical module supports 10/100/1000 adaptive and Auto MDI/MDIX, and can be used with category 5 unshielded network patch cords; the transmission distance can reach 100m.

The 1000BASE-SX SFP optical module is compatible with the IEEE 802.3z 1000BASE-SX standard, and can be used in a 50μm/62.5μm multimode optical fiber link with a maximum transmission distance of 550m.

2. Long-distance network wiring

1000BASE-EX and 1000BASE-ZX SFP optical modules can be used with single-mode optical fibers and are suitable for long-distance network transmission. The transmission distance of 1000BASE-EX SFP optical modules can reach 40km, and the transmission distance of 1000BASE-ZX SFP optical modules can reach 80km.

Note: When single-mode fiber (SMF) is used for a short distance, in order to avoid overload of the receiver, an optical attenuator needs to be inserted in the link.


The SFP port can support both SFP electrical port modules and SFP optical port modules. Both SFP ports and SFP optical modules have high flexibility and compatibility in practical applications and are the best solution for Gigabit Ethernet.