Introduction to Three Cisco SFP Module Types

Although the 10 Gigabit Ethernet system has become the dominant deployment in telecommunication market, there are still many 1GbE infrastructures existing in today’s networks. SFP optical transceiver, as a critical component to support 1G data transmission, is also increasingly required in most Gigabit Ethernet networks. Many vendors, like Cisco, one of the most well-known and reliable company in telecommunication industry, have provided various types of SFP transceiver modules to the market. This post aims to introduce three common Cisco SFP module types for you references.

SFP Optical Transceiver Overview

SFP (small form factor pluggable) transceivers are hot-plugable and compact optical transceivers which provide instant fiber or copper connectivity for SONET, Gigabit Ethernet, Fibre Channel, and other communications standards. They are a cost-effective way to connect a single network device to a wide variety of fiber cable distances and types. With the existence of SFP module, network upgrades could be easier, since SFP is interchangeable fiber connectors that can adapt to any existing network. For example, by simply replacing the pluggable optical transceiver, a media converter that was originally used in a multimode network can be re-configured to operate over a CWDM network. SFP optics come in four versions: 1000Base-T, 1000Base-SX, 1000Base-LX, and 1000Base-ZX. The 1000Base-SX will work on multimode fiber for the link length of 550 m, while the 1000Base-LX and 1000Base-ZX work only on single-mode fiber for the maximum distance of 10 km and 80 km respectively, and the 1000Base-T is the RJ-45 version. The following image shows the structure of SFP module.

Three Common Cisco SFP Module Types

GLC-SX-MM SFP: GLC-SX-MM 1000Base-SX SFP is a duplex SFP transceiver used over multimode fiber at the wavelength of 850 nm for optical communications. It is compatible with IEEE 802.3z and could support the data rate of 1Gbps for the reach of 550 meters over 50/125 multimode fiber, and 220 meters over 62.5/125 multimode fiber. But since March 8th, 2013, there is no longer GLC-SX-MM SFP modules on sale in Cisco. It is replaced by the new model SFP transceiver module—GLC-SX-MMD SFP. However, for usage and cost considerations, many users still use the old model SFP, because GLC-SX-MMD is much more expensive, and except the additional DOM function, they work as the same when used in Cisco switch. These old Cisco compatible GLC-SX-MM SFPs can be still purchased in Fiberstore at very lower prices as shown in the following image.

GLC-LX-SM SFP: GLC-LH-SM 1000Base-LX-LH Ethernet transceiver is a LC duplex SFP transceiver used for optical networks. It operates at 1310 wavelength, rated for distances up to 10 km and a maximum bandwidth of 1Gbps. This type of SFP module is compliant with MSA (multisource agreement) and the IEEE 802.3z 1000Base-LX standard, which can both operate over single-mode fiber for the link spans of up to 10 km and up to 550 m on any multimode fibers. The following picture is Cisco GLC-LH-SM-15 Compatible 1000BASE-LXLH SFP in Fiberstore.

GLC-T SFP: GLC-T (as shown below) is a type of copper SFP module used over standard Cat5 unshielded twisted pair copper cabling of link length up to 100 m (328ft). It provides 1Gbps data transfer and offers full-duplex Gigabit Ethernet connectivity to high-end workstations and between wiring closets over existing copper network infrastructure. Cisco GLC-T SFP transceiver module can offer a flexible and simple method to be installed into SFP MSA compliant ports at any time with no interruption of the host equipment operation. It enables for seamless integration of fiber with copper LAN connections wherever SFP interface slots can be found.

Summary

We have mentioned three commonly used Cisco SFP modules in the previous text, and each module is applied in different applications. GLC-SX-MM SFP is used for multimode fiber based equipment, while GLC-LX-SM SFP is more suitable for single-mode fiber based infrastructure and GLC-T SFP is often deployed with copper cable, like Cat5 Ethernet cable. Besides these aspects, you should also take your budget into consideration. As we all know, Cisco brand SFP transceiver is expensive, but with the increasing popularity of third-party modules, we have a good alternative. Fiberstore provides a wide range of Cisco compatible SFP modules at affordable prices. If you have related needs, please visit FS.COM for more information.