Three Cisco SFP Module Types Brief Introduction

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 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 Fiber-mart 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 Fiber-mart.

 

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. Fiber-mart
provides a wide range of Cisco compatible SFP modules at affordable prices. If
you have related needs, please visit fiber-mart.COM for more information.