A Brief Introduction to Cisco Single-Mode SFP Modules


Small form-factor pluggable (SFP) module is a hot-pluggable interface transceiver which links switches and routers to network. These small, modular optical interface transceivers offer a convenient and cost effective solution for the adoption of Gigabit Ethernet and Fibre Channel in data center. Cisco’s industry-standard SFPs can be used and interchanged on a wide variety of Cisco products and can be intermixed in combinations of IEEE 802.3z compliant 1000BaseSX, 1000BaseLX/LH, or 1000BaseZX interfaces on a port-by-port basis. Cisco SFP modules are commonly available in several different types: 1000BASE-T, 1000BASE-SX, 1000BASE-LX/LH, 1000BASE-EX, 1000BASE-ZX, and 1000BASE-BX-D/U. This post will give an introduction to Cisco single-mode SFP modules.

Cisco 1G single-mode SFP

Cisco 1G Single-Mode SFP Modules

Cisco 1G single-mode SFP modules consist of 1000BASE-LX/LH, 1000BASE-EX, 1000BASE-ZX, 1000BASE-BX-U, 1000BASE-BX-D, GLC-BX40-D-I, GLC-BX40-DA-I, GLC-BX40-U-I, GLC-BX80-D-I, and GLC-BX80-U-I. The 1000BASE-LX/LH SFP is compatible with the IEEE 802.3z 1000BASE-LX standard, functions on single-mode fiber-optic link and its transmission range can cover 550 m to 10 km on any multimode fibers. 1000BASE-EX SFP functions on standard single-mode fiber-optic link with spanning up to 40 km in length. 1000BASE-ZX SFP functions on standard single-mode fiber-optic link and its transmission range reaches approximately 70 km in length.

The 1000BASE-BX-D and 1000BASE-BX-U SFPs which are compatible with the IEEE 802.3ah 1000BASE-BX10-D and 1000BASE-BX10-U standards function on a single strand of standard SMF (Single-Mode Fiber) and its operating transmission range covers up to 10 km. The Cisco GLC-BX40-D-I, GLC-BX40-DA-I, and GLC-BX40-U-I SFPs also operate on a single strand of standard SMF and its transmission range can reach 40 km. A GLC-BX80-D-I and GLC-BX80-U-I device function on a single strand of standard SMF with an operating transmission range up to 80 km.

Another difference between these SFP modules is the transmission direction: 1000BASE-LX/LH, 1000BASE-EX and 1000BASE-ZX’ transmission is duplex while 1000BASE-BX-U, 1000BASE-BX-D, GLC-BX40-D-I, GLC-BX40-DA-I, GLC-BX40-U-I, GLC-BX80-D-I, and GLC-BX80-U-I’s transmission is simplex. One thing they have in common is that all these Cisco single-mode SFP modules adopt LC interfaces and Cisco SFP 1G transceivers can transmit optical signals through simplex or duplex LC patch cable.

Transmission of a Single Strand of SMF

Features and Benefits

Cisco single-mode SFP modules feature a variety of different types of modules supporting different transmission ranges and direction, and they are also compatible with products of other categories. The hot-swappable input/output device directly plugs into an Ethernet SFP port of a Cisco switch, which maximizes uptime and simplifies serviceability when installing or replacing. The robust design enhances capability and the small factor features great density per chassis. Its flexibility of media and interface choice on a port-by-port basis bring you convenience. “Pay as you Populate” model lowers initial costs. It can support digital optical monitoring (DOM) capability for strong diagnostic capabilities. Cisco quality identification (ID) feature enables a Cisco platform to identify whether the module is certified and tested by Cisco and it can be interoperable with other IEEE-compliant 1000BASE interfaces where applicable.


This post briefly introduces Cisco single-mode SFP modules, covering its definition, types of these SFPs and introduction of each type, and features and benefits of Cisco single-mode SFP modules. Now there are a number of modules for you to choose, but be sure to find the right one based just on your needs and at the same time take a few factors into consideration.

1000BASE-X SFP Modules Overview

A continuous stream of manufacturing process improvements and product innovations has given fiber optical system several advantages, like longer distance reach, larger data-carrying capacity, greater bandwidth and lower power consumption. Among these fiber optical product innovations, hot-pluggable transceiver modules should come to the central point with their unique designs. They have been constantly designed, and finally been reinvented as hot-pluggable modules along with the optical technological advances. These small, hot-pluggable serve as the key components in accommodating the demands of higher port density and more networking flexibility.

Transceiver modules come into various types: SFP (small form-factor pluggable), SFP+ (small form-factor pluggable plus), QSFP+ (quad small form-factor pluggable plus), etc. This article mainly introduces SFP transceiver modules which are widely applied in Gigabit Ethernet (GbE) applications, with the focus on several 1000BASE-X interface types, including 1000BASE-SX, 1000BASE-LX, 1000BASE-EX, and 1000BASE-BX10-D/U.

Features and Benefits

1000BASE-X SFP modules provide a wide range of form factor options for enterprise and service provider needs. They are designed with the following features and benefits:

  • Hot swappable to maximize uptime and simplify serviceability;
  • Flexibility of media and interface choice on a port-by-port basis, so you can “pay as you populate”;
  • Sophisticated design for enhanced reliability;
  • Supports digital optical monitoring (DOM) function;
1000BASE-X SFP Interface Types


1000BASE-SX SFP, compatible with the IEEE 802.3z 1000BASE-SX standard, operates on legacy 50μm multi-mode fiber (MMF) links up to 550m and on 62.5μm Fiber Distributed Data Interface (FDDI)-grade MMFs up to 220m. Take DEM-311GT for example, Fiberstore compatible D-Link 1000BASE-SX SFP is able to realize 550m link length through OM2 MMF with duplex LC.

DEM-311GT, D-Link 1000BASE-SX SFP


1000BASE-LX SFP, compatible with the IEEE 802.3z 1000BASE-LX standard, is specified to support link length of up to 10km on standard single-mode fiber (SMF), to 550m on MMFs. When used over legacy MMF, the transmitter should be coupled through a mode conditioning patch cable. The laser is launched at a precise offset from the center of the fiber which causes it to spread across the diameter of the fiber core, reducing the effect known as differential mode delay which occurs when the laser couples onto only a small number of available modes in MMF.


1000BASE-EX, sometimes referred to as LH, is a non-standard but industry accepted standard which works on standard SMF with fiber link spans up to 40km in length. For back-to-back connectivity, a 5-dB inline optical attenuator should be inserted between the fiber optic cable and the receiving port on the SFP at each end of the link. 1000BASE-EX SFPs (eg. GLC-EX-SMD) run on 1310nm wavelength lasers, and achieves 40km link length.


The 1000BASE-BX-D and 1000BASE-BX-U SFPs, compatible with the IEEE 802.3ah 1000BASE-BX10-D and 1000BASE-BX10-U standards, operate on a single strand of standard SMF (figure shown below). A 1000BASE-BX10-D device is always connected to a 1000BASE-BX10-U device by a single strand of standard SMF with an operating transmission distance up to 10km.


The communication over a single strand of fiber is accomplished by separating the transmission wavelength of the two devices (figure shown above): 1000BASE-BX10-D transmits a 1490nm channel and receives a 1310nm signal, whereas 1000BASE-BX10-U transmits at a 1310-nm wavelength and receives a 1490-nm signal. In this figure, the wavelength-division multiplexing (WDM) splitter is integrated into the SFP to split the 1310nm and 1490nm light paths.


These 1000BASE-X SFP modules provide physical layer connectivity for optical-port modular switch IO blades and optical-port stackable switches, reliable, and cost-effective choices to accommodate varied and evolving network demands. As a professional fiber optic product manufacturer and supplier, Fiberstore supplies all the above-mentioned several 1000BASE-X SFP modules which are all test- and quality-assured. You can visit Fiberstore for more information about 1000BASE-X SFP modules.