SFP 40 km VS. DWDM SFP: Which to Choose?

Small Form-factor Pluggable (SFP) is a compact, hot-pluggable transceiver used for both telecommunication and data communications applications. It is also called mini-GBIC for its smaller size, which is the upgraded version of GBIC transceiver. These 1Gb SFP modules are capable of supporting speeds up to 4.25 Gbps. And they are most often used for Fast Ethernet of Gigabit Ethernet applications. It interfaces a network device motherboard (for a switch, router, media converter or similar device) to a fiber optic or copper networking cable. SFP modules are commonly available in several different categories: 1000BASE-T SFP, 1000BASE-EX SFP, 1000BASE-SX SFP, 1000BASE-LX/LH SFP, 1000BASE-BX SFP, 1000BASE-ZX SFP, CWDM SFP and DWDM SFP. These modules support different distance according to the different Gigabit Ethernet standard. Today’s main subject will discuss SFP 40 km vs. DWDM SFP.

FS.COM Optical Transceivers

SFP 40 km

SFP 40 km transceiver is designed for highly reliable fiber optic network links up to 40 km. It is a cost effective transceiver designed to enable 1Gb for data center and core network applications. 1000BASE-EX SFP is the most popular SFP 40 km transceiver which runs on 1310nm wavelength lasers and achieves 40km link length. Except that, 1000BASE-BX BiDi SFP, 1000BASE-LH SFP and 1000BASE-LX SFP can also realize the transmission distance up to 40 km. The following will introduce these 1GbE SFP 40 km transceivers respectively.

1000BASE-EX SFP 40 km

1000BASE-EX SFP transceiver module is designed to connect a Gigabit Ethernet port to a network and has dual LC/PC single mode connectors. It operates on standard single-mode fiber-optic link spans of up to 40 km in length. The SFP Ethernet module provides a dependable and cost-effective way to add, replace or upgrade the ports on switches, routers and other networking equipment. Cisco GLC-EX-SM1550-40 and Cisco GLC-EX-SMD are 1G single mode fiber SFP 40 km modules for 1000BASE-EX Gigabit Ethernet transmission. GLC-EX-SM1550-40 supports a 1550nm wavelength signaling, while GLC-EX-SMD supports a 1310nm wavelength signaling.

SFP 40 km

1000BASE-BX SFP 40 km

1000BASE-BX SFP is a kind of BiDi transceiver, which can be divided into 1000BASE-BX-D SFP and 1000BASE-BX-U SFP. These two SFP transceivers must be used in pairs to permit a bidirectional Gigabit Ethernet connection using a single strand of single mode fiber (SMF) cable. The 1000BASE-BX-D SFP operates at wavelengths of 1490nm TX/1310nm RX, and the 1000BASE-BX-U SFP operates at wavelengths of 1310nm TX/1490nm RX.

  • 1000BASE-BX-D BiDi SFP 40 km

Cisco GLC-BX40-D-I and GLC-BX40-DA-I are pluggable fiber optical transceivers for Gigabit Ethernet 1000BASE-BX and Fiber Channel communications. They support link length of up to 40 km point to point on single mode fiber at 1Gbps bidirectional and use an LC connector. The GLC-BX40-D-I transceiver transmits a 1490nm channel and receives a 1310nm signal, whereas GLC-BX40-DA-I transmits at a 1550nm wavelength and receives a 1310nm signal.

  • 1000BASE-BX-U BiDi SFP 40 km

Similar to 1000BASE-BX-D 40 km SFP , Cisco GLC-BX40-U-I and GLC-BX40-UA-I also support link length of up to 40 km point to point on single mode fiber at 1Gbps bidirectional and use an LC connector. The main difference is the wavelength: GLC-BX40-U-I transmits a 1310nm channel and receives a 1550nm signal, whereas GLC-BX40-UA-I transmits at a 1310nm wavelength and receives a 1490nm signal. A GLC-BX40-D-I or GLC-BX40-DA-I device connects to a GLC-BX40-U-I or GLC-BX40-UA-I device with a single strand of standard SMF with an operating transmission range up to 40 km.

1000BASE-LX SFP 40 km

1000BASE-LX is a standard specified in IEEE 802.3 Clause 38 which uses a long wavelength laser. The “LX” in 1000BASE-LX stands for long wavelength, indicating that this version of Gigabit Ethernet is intended for use with long-wavelength transmissions (1270 – 1355nm) over long cable runs of fiber optic cabling. Allied Telesis AT-SPLX40 and Allied Telesis AT-SPLX40/1550 are 1000BASE-LX SFP single-mode modules supports Gigabit Ethernet over single-mode cables at distances up to 40 km. AT-SPLX40 operates over a wavelength of 1310nm for 40 km, whereas AT-SPLX40/1550 operates over a wavelength of 1550nm.

1000BASE-LH SFP 40 km

Unlike 1000BASE-LX, 1000BASE-LH is just a term widely used by many vendors. Long Haul (LH) denotes longer distances, so 1000BASE-LH SFP modules operate at a distance up to 70 km over single mode fiber. Cisco Linksys MGBLH1 is a easy-to-install modules that provide a simple way to add fiber connectivity or to add an extra Gigabit Ethernet port to switches. The MGE transceiver can support distances up to 40 km over single-mode fiber at a 1310nm wavelength.


DWDM SFP transceivers are used as part of a DWDM optical network to provide high-capacity bandwidth across an optical fiber network, which is a high performance, cost effective module for serial optical data communication applications up to 4.25Gb/s. DWDM transceiver uses different wavelengths to multiplex several optical signal onto a single fiber, without requiring any power to operate. There are 32 fixed-wavelength DWDM SFPs that support the International Telecommunications Union (ITU) 100-GHz wavelength grid. The DWDM SFP can be also used in DWDM SONET/SDH (with or without FEC), but for longer transmission distance like 200 km links and Ethernet/Fibre Channel protocol traffic for 80 km links. Cisco C61 DWDM-SFP-2877-40 is a 1000BASE-DWDM SFP 40km transceiver, which is designed to support distance up to 40 km over single-mode fiber and operate at a 1528.77nm DWDM wavelength (Channel 61) as specified by the ITU-T.



  • Transmission Medium

Generally, the standard SFP 40 km transceivers transmit through the single mode fiber, while DWDM SFP carries signals onto a single optical fiber to achieve maximum distances by using different wavelengths of laser light. So the DWDM SFP transceivers do not require any power to operate.

  • Wavelength

The standard SFP 40 km transceivers support distances up to 40 km over single-mode fiber at a 1310nm/1550nm wavelength. (the BiDi SFP has 1490nm/1550nm TX & 1310nm RX or 1310nm TX & 1490nm/1550nm RX ). However, DWDM SFP operates at a nominal DWDM wavelength from 1528.38 to 1563.86nm onto a single-mode fiber. Among them, 40 km DWDM SFP operates at a 1528.77nm DWDM wavelength (Channel 61).

  • Application

DWDM SFP is used in DWDM SONET/SDH, Gigabit Ethernet and Fibre Channel applications. These modules support operation at 100Ghz channel. The actual SFP transceiver offers a transparent optical data transmission of different protocols via single mode fiber. And 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.

  • Price

DWDM provides ultimate scalability and reach for fiber networks. Boosted by Erbium Doped-Fiber Amplifiers (EDFAs)  – a sort of performance enhancer for high-speed communications, DWDM systems can work over thousands of kilometers. Most commonly, DWDM SFP is much more expensive than the standard SFP. You can see the price more clearly in the following cable.



1000BASE SFP transceiver is the most commonly used component for Gigabit Ethernet application. With so many types available in the market, careful notice should be given to the range of differences, both in distance and price of multimode and single-mode fiber optics. Through SFP 40 km vs. DWDM SFP, if you are looking for SFP modules over long distance and with better scalability, DWDM SFP module is the ideal choice.

Related Article: SFP Transceiver: To Be or Not To Be?

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.

Related Article:Introduction to Single Strand Fiber Solution