Category Archives: Optical Transceiver Solution

Differences Between QSFP-40G-SR4, QSFP-40G-CSR4 and QSFP-40G-CR4

When selecting 40G fiber optic transceivers, customers are easily confused by the standards and models of the 40G modules. This is because the standards of transceiver are generally the combinations of letters and numbers. Some of the standards and models are really similar to each other. Thus, this post is to offer an illustration of three 40G modules whose standards and models are easily misidentified. These 40G modules are QSFP-40G-SR4, QSFP-40G-CSR4 and QSFP-40G-CR4. Details of the three modules will be firstly introduced separately. Then comparison in specific applications among them will be offered.

QSFP-40G-SR4 (40Gbase-SR4)

The three standards look similar. However, they actually have great differences from each other. Here starts from 40Gbase-SR4. Many vendors use “QSFP-40G-SR4” to identify 40G QSFP+ modules that support by 40Gbase-SR4 standards. 40Gbase-SR4 QSFP+ is the most popular 40G fiber optic transceiver for transmission in short distances. 40GBASE-SR4 QSFP+ module supports link lengths of 100m and 150m, respectively, on OM3 and OM4 multimode fibers. It is a parallel fiber optic transceiver containing a MTP/MPO interfaces, which use 4*10G transmission pattern. With four 10G SFP+ lane in one module, QSFP-40G-SR4 can achieve 40G optical signal transmitting and receiving at the same time via a ribbon fiber cable. The following picture shows how signals are transmitted over a MTP ribbon fiber cable.

40G-SR4 transmission

QSFP-40G-CSR4 (40Gbase-CSR4)

The working principle of QSFP-40G-CSR4 module is similar to QSFP-40G-SR4 module. Both QSFP-40G-CSR4 module and QSFP-40G-SR4 module has MTP/MPO interface. However, 40Gbase-CSR4 module can be regarded as an upgraded version of the 40Gbase-SR4 module. It can support longer 40G transmission up to 300m on OM3 and 400m on OM4. Transmission distance is the biggest different form the two 40G fiber optic transceivers.

QSFP-40G-CR4 (40Gbase-CR4)

QSFP-40G-CR4 module is very much different from the above mentioned two 40G modules. It is a pre-terminated copper cable with both ends terminated with QSFP+ connector. It is known as 40G QSFP+ cable or 40G QSFP+ direct attach cable. Limited by the property of copper cable, QSFP-40G-CR4 can only reach a transmission distance of 7 meters.


Which One Should You Choose QSFP-40G-SR4, QSFP-40G-CSR4 or QSFP-40G-CR4?

As the above mentioned, QSFP-40G-SR4, QSFP-40G-CSR4 and QSFP-40G-CR4 are all designed for 40G transmission in short distances. Which one is better for your applications? This should be decided by the specific applications. Generally, there are two types of transmission in 40G network: 40G to 40G transmission and 40G to 10G transmission. All the three modules can accomplish the two applications. However, there are some differences.

40Gbase SR4

QSFP-40G-SR4 and QSFP-40G-CSR4 uses the same connection methods for 40G-40G and 40G-10G transmission. For 40G to 40G connections, a length of MTP trunk cable can be used to connect two QSFP-40G-SR4 or QSFP-40G-CSR4 modules to form the whole link. The following picture takes Cisco Nexus 9396PX 40G connection as an example. For 40G to 10G connection, a MTP-8LC harness cable can be used to connect a QSFP-40G-SR4 or QSFP-40G-CSR4 module with other 10G devices.

40G to 40G connection with QSFP-40G-CSR4

For 40G QSFP+ to QSFP+ direct attach cable (DAC), no additional fiber patch cables are need for 40G to 40G connection. Directly insert the two QSFP+ connector in to the devices, 40G transmission can be achieved. For 40G to 10G transmission, another version of QSFP+ DAC can be used, which is known as QSFP+ to 4 SFP+ direct attach cable. The following picture shows how to connect a 40G port to four 10G port by using a QSFP+ to 4 SFP+ copper cable.

40G to 10G connection

If your transmission distance is less than 150 meters but longer than 7 meters, then QSFP-40G-SR4 module would be the best choice. If your transmission distance is longer than 150 meters, QSFP-40G-CSR4 module is suggested for better network performance. If the transmission distance is less than 7 meters, then QSFP-40G-CR4 modules would be the most cost-effective solutions.

Related Articles: How to Connect 40G QSFP+ SR4 Transceivers to Network?

                              40G Transceiver Module: QSFP+ Module And CFP Module

Brocade 40G Switch ICX 7750-26Q Cabling Solution

The Brocade ICX 7750 is a series of switches which can provide high-availability capabilities and flexible stacking architecture for 10/40G applications. Brocade ICX 7750 series switches are usually used for 10/40G aggregation and core distribution. Brocade ICX 7750-26Q is a member of Brocade ICX 7750 series, which is a 1U high performance switch with up to 32 40G QSFP+ ports (six optional). This post will offer optics and cabling solution for Brocade ICX 7750-26Q switches.

Brocade ICX 7750-26Q transceivers

Basic of Brocade ICX 7750-26Q Switch

The above picture shows a Brocade ICX 7750-26Q switch from FS.COM testing center. On the front panel of Brocade ICX 7750-26Q switch, there are 26 40G QSFP+ ports, ICX 7750-6Q module with 6 40G QSFP+ ports can be added on the rear panel of this switch. Thus up to 32 40G QSFP+ ports can be supplied by Brocade ICX 7750-26Q switch. It can support transmission applications for both 40G to 40G and 40G to 10G.

Brocade ICX 7750-26Q 40G to 40G Applications

Brocade ICX 7750-26Q can support 40G transmission for both short distances and long distances by using different 40G QSFP+ transceivers and fiber optic cables. The following picture shows the cabling methods for 40G point to point connection. Choosing the proper fiber patch cable for two QSFP+ modules, 40G data transmission between two Brocade ICX 7750 switches can be achieved. In this case, two Brocade 40G-QSFP-LR4 compatible transceivers and a length of LC to LC duplex single-mode fiber patch cable are being used.

brocade-icx7750 40G connection

Brocade compatible QSFP+ to QSFP+ direct attach cables including (direct attach copper cables and active optical cables) are cost-effective alternatives for Brocade ICX 7750-26Q 40G connections in short distances.


Brocade ICX 7750-26Q 40G to 10G Applications

As mentioned Brocade ICX 7750-26Q switch can also support 40G to 10G applications. A 40G QSFP+ port can be splitted into four 10G SFP+ ports, which can achieve transmission between 10G and 40G. There is a wide selection of Brocade ICX 7750-26Q switch 40G to 10G connections. Fanout assemblies play an important role to support these connections.

brocade-icx7750 40G connection

The above picture shows the commonly used connection methods for Brocade ICX 7750-26Q 40G to 10G connections. In this case, Brocade QSFP-40G-PLRL4 compatible transceiver is being used one the Brocade ICX 7750-26Q side. A length of MTP to four duplex LC breakout cable is being used to connect Brocade QSFP-40G-PLRL4 with four 10G SFP+ transceivers inserted in several 10G switches on the opposite side. Also, QSFP+ to SFP+ DACs and AOCs can also be used.

Brocade 40G-QSFP-SR4

Brocade ICX 7750-26Q Fiber Optic Transceivers and Cabling Solutions

Brocade ICX 7750-26Q switch provides flexible and high density networking environments. This post only provides the optics and cabling solution for Brocade ICX 7750-26Q switch. The following table listed the Brocade ICX 7750-26Q compatible transceivers and cables for you references. Kindly visit FS.COM Transceiver modules for BROCADE ICX 7750 page for more details about Brocade ICX 7750 series switches, if you are interested.

Brocade Compatible Modules Description
40G-QSFP-LR4 40GBASE-LR4 QSFP+ optic (LC), for up to 10 km over SMF
40G-QSFP-SR4 40GBASE-SR4 QSFP+ optic (MTP), 100 m over MMF
40G-QSFP-SR4-INT 40GBASE-SR4 QSFP+ optic (MTP), 100 m over MMF, compatible with 10GB BASE-SR
40G-QSFP-QSFP-C-0101 40 GbE direct-attached QSFP+ to QSFP+ active copper cable, 1 m
40G-QSFP-QSFP-C-0301 40 GbE direct-attached QSFP+ to QSFP+ active copper cable, 3 m
40G-QSFP-QSFP-C-0501 40 GbE direct-attached QSFP+ to QSFP+ active copper cable, 5 m
40G-QSFP-QSFP-AOC-0101 40 GbE direct-attached QSFP+ to QSFP+ active optical cable, 1 m
40G-QSFP-QSFP-AOC-0301  40 GbE direct-attached QSFP+ to QSFP+ active optical cable, 3 m
40G-QSFP-QSFP-AOC-0501 40 GbE direct-attached QSFP+ to QSFP+ active optical cable, 5 m
40G-QSFP-4SFP-C-0101 4×10 GbE direct-attached QSFP+ to 4 SFP+ copper breakout cable, 1m
40G-QSFP-4SFP-C-0301 4×10 GbE direct-attached h QSFP+ to 4 SFP+ copper breakout cable, 3m
40G-QSFP-4SFP-C-0501 4×10 GbE direct-attached QSFP+ to 4 SFP+ copper breakout cable, 5m
40G-QSFP-4SFP-AOC-0101  4×10 GbE direct-attached QSFP+ to 4 SFP+ active optical cable, 1m
40G-QSFP-4SFP-AOC-0301 4×10 GbE direct-attached QSFP+ to 4 SFP+ active optical cable, 3m
40G-QSFP-4SFP-AOC-0501  4×10 GbE direct-attached QSFP+ to 4 SFP+ active optical cable, 5m

How to Select 10G SFP+ Modules for Cisco Switches?

10G fiber optic network is being widespread in today’s telecommunication network. A lot of 10G fiber optic devices like switches are being uses, among which Cisco devices are the most commonly used according to statistics. If you choose a Cisco switch, Cisco original brand or Cisco compatible modules like SFP/SFP+ might be needed for transferring between optical signals and electrical signals. This post will offer details about how to select the proper 10G SFP+ module for Cisco compatible modules

Understand 10G IEEE Standards and How Cisco Name Its Modules

10G fiber optic network is mature now, and there is a wide selection of 10G IEEE standards for different 10G networking applications and environments. Before you buy 10G SFP+ modules for your Cisco switches, you should firstly get to know these 10G standards.

10G IEEE Standards

IEEE has defined 10G standards for different transmission distance and transmission media. For instance, there are 10GBASE-SR SFP+ for short distance up to 300 meters over OM3 multimode optical fiber and 10GBASE-LR for long distance up to 10 kilometers over single-mode fiber. There are also standards for 10G transmission over copper cables like 10GBASE-CR and 10GBASE-T. The following table listed the details for the most commonly used 10G standards.

10G IEEE Standards Description
10GBASE-SR Support 10G transmission over wavelength of 850nm via multimode fiber
in short distances: OM3 (up to 300m) and OM4 (up to 400m).
10GBASE-LR Support 10G transmission over single-mode fiber up to 10km
over wavelength of 1310nm.
10GBASE-LRM Support 10G transmission over standard multimode fiber up to 200m
over wavelength of 1310nm.
10GBASE-ER Operate over 1550nm wavelength and support transmission distance up
to 40km over single-mode fiber. Attenuation is required for transmission
distance shorter than 20km.
10GBASE-ZR Support 10G transmission over 1550nm single-mode fiber optic up to 80km.
For short links, attenuation is required to ensure transmission quality.
10GBASE-BX Support duplex 10G transmission over a single single-mode fiber using
two different wavelengths up to 80km.
10G CWDM/DWDM Support 10G transmission over 1550nm single-mode fiber optic up to 80km.
For short links, attenuation is required to ensure transmission quality.
10GBASE-CR Support 10G transmission over Twinax copper cable in very short distance
and offer a cost-effective way for connections within racks.

Product Name of Cisco 10G SFP+ Modules

The naming system of Cisco 10G SFP+ modules is closely related to the IEEE standards. Here I listed several examples for Cisco SFP+ module to better illustrate how Cisco names its 10G SFP+ modules.

10G IEEE Standards Cisco 10G Modules Product Number Example
10GBASE-BX Cisco SFP-10G-BXD-I & SFP-10G-BXU-I; Cisco SFP-10G-BX40D-I & SFP-10G-BX40U-I
10G CWDM/DWDM Cisco CWDM-SFP10G-1470; Cisco DWDM-SFP10G-61.41

For common 10G SFP+ modules, Cisco uses the key words of the standards to name the responding modules. For special modules, Cisco has built another naming system.

SFP+ module

For a pair of BiDi SFP+ modules, letter “D” and “U” is used to the two modules that are used together on each end of the fiber optic link. For instance, SFP-10G-BXD-I & SFP-10G-BXU-I is a pair of BiDi Modules that can support transmission distance up to 10km. Additional numbers are added to mark the transmission distance of the BiDi modules. SFP-10G-BX40D-I & SFP-10G-BX40U-I is a pair of BiDi SFP+ modules that can support transmission distance up to 40km.

For CWDM 10G SFP+ and DWDM SFP+, the wavelength is added in the part number. For instance, CWDM-SFP10G-1470 is the part number of a CWDM SFP+ that is operated at wavelength of 1470nm. If you want a CWDM SFP+ operating over 1550nm, then the product number of this CWDM module should be CWDM-SFP10G-1550. As all the DWDM SFP+ modules are operated over wavelengths around 1500nm, in the product number of Cisco DWDM SFP+ modules, the first two number 1 and 5 is eliminated. For example, DWDM-SFP10G-61.41 stands for a DWDM SFP+ transceiver with operating wavelength of 1561.41nm.


For modules like SFP+ direct attach cable (SFP+ DAC) and SFP+ active optical cable (SFP+ AOC) which contains a length of cables, Cisco combines the characters of IEEE standard and number to name its modules. Cisco SFP-H10GB-CU1M stands for 10G SFP+ direct attach copper cable that is one-meter long. Cisco SFP-10G-AOC2M is a 2-meter long 10G SFP+ active optical cable.

Do You Really Need Cisco Original Brand SFP+ Module?

Except IEEE standard and transmission distance, to select the proper 10G SFP+ module should also considerate several other factors like compatibility and costs.

Although Cisco has a wide selection of switches and 10G SFP+ modules, but not every SFP+ modules can work well on every Cisco switches SFP+ port. Before selecting the SFP+ msodule for your Cisco switch, you must make sure this SFP+ is compatible with your switch.

The second important factor is the costs for the SFP+ modules. Why? SFP+ module is just a small part of the whole fiber optic network, but the use amount of SFP+ module is very large. Cisco Original brand SFP+ modules are usually expensive. Thus, select cost-effective modules are necessary. Actually, Cisco Original brand SFP+ module is not the only choice. There are also many third party modules that it compatible with Cisco switches. Generally, prices of third party fiber optic transceivers are much lower than the original brand ones.

How to Buy Cisco 10G SFP+ Module?

If you have plenty of money, you can directly order the modules from Cisco. However, if you are going to select the third party modules for a cost-effective solution, then the quality and compatibility would be very important. FS.COM is a provider offers a full range of Cisco compatible modules. All its modules are fully tested in original brand switches to ensure the compatibility and quality. What’s more, FS.COM uses the same naming system as Cisco for its Cisco compatible modules and generic fiber optic modules. A list is also offered in the product page of each fiber optic modules showing the compatible switches and platforms. Customer can use the Cisco product number to search Cisco Compatible and generic modules in FS.COM directly.

Related Article:

Cisco SFP-10G-SR: All You Need to Know

A Comprehensively Understanding of Cisco 10GBASE SFP+ Modules

Increase Network Capacity With BiDi Fiber Optic Modules

BiDi Fiber

Adding more fiber optic cable in the existed fiber optic network is a time and money consuming method to increase the transmission capacity of the network. In most cases, server providers cannot provide that much money and customers do not want to wait that long. To increase the fiber optic network capacity, BiDi fiber optic modules are being suggested for a variety of situations, which can support duplex transmission over a single strand of optical fiber. Now there are a lot of fiber optic transceivers designated with BiDi technologies to increase the network capacity. This post will introduce the most commonly used BiDi modules.

10G BiDi SFP+ 1270-1330

Working Principle of BiDi Fiber Optic Transceivers

Generally, most fiber optic transceivers use two fibers for duplex transmission. However, most BiDi fiber transceivers use two different wavelengths to carry the duplex signals separately. In simple, the two wavelengths are just like two fibers. The optical signals for transmission and receiving are separately converted into signals of specific wavelengths. This is why most BiDi transceivers can support duplex transmission over a single fiber. The following picture shows the basic working principle of a BiDi transceiver.

BiDi transceiver working principle

Commonly Used BiDi Fiber Optic Transceiver

Generally, BiDi transceivers can be divided according to the data rate and package form factors. Currently, the most commonly used BiDi fiber modules can support a data rate ranging from 1G to 40G, and are available in diverse form factor like SFP, SFP+ and QSFP+.


For 1G BiDi transceiver, 1G BiDi SFP, also known as 1000BASE-BX SFP modules are often used in today’s network. One thing should be noticed before using BiDi modules, is that the BiDi modules should be used in pairs. As mentioned that BiDi modules use two different wavelengths for transmission. For instance, on one side of you use a BiDi SFP (Tx1310nm/Rx1490nm), on the other side a BiDi fiber SFP using 1490 nm for transmission and 1310 nm for receiving is required. A length of simplex single-mode LC to LC fiber cable is usually used to connect this pair of BiDi SFP module to achieve the connection.

LC/UPC simplex SMF

10G BiDi SFP+ modules also have a simplex LC interface, which is also used in pairs and connected by simplex LC fiber cable. Generally, BiDi fiber transceiver can support a long transmission distance. To select the right 10GBASE-BX SFP+ module, wavelength and transmission distance are two important factors to be considered. Currently, 10G BiDi SFP+ modules using 1270nm and 1330 nm for transmission are most commonly used for 10G transmission. 10GBASE-BX SFP+ modules that support transmission distances of 10km, 20km, 40km and 80km are more popular according to statistic from FS.COM. Cisco compatible 10GBASE-BX20-D/U SFP+ and 10GBASE-BX10-D/U SFP+ are the most popular among all the third party 10G BiDi SFP+ modules.

10G BiDi SFP 1330-1270

There are also 10GBASE-BX SFP+ modules in other form factors, like 10G BiDi X2 (10GBASE-BX X2) modules. However, these modules are gradually exiting the market with the upgrading of the devices.


Unlike other BiDi fiber transceiver like 1000BASE-BX SFP and 10GBASE-BX SFP+, QSFP-40G-SR-BD module has a duplex LC interface. It uses BiDi technologies to achieve four strands of 10G optical signals over a duplex multimode LC fiber patch cable over two different wavelengths. My article (Using 10G Infrastructure for 40G Ethernet With 40G BiDi Optics) has introduced this module in details. The following shows the basic working principle of QSFP-40G-SR-BD. This module can achieve transmission distance up to 150 meters over OM4, 100 meters over OM3 and 30 meters over OM2.


BiDi Module Solutions

Using BiDi fiber modules to increase the capacity of the existing fiber optic network is more effective in both time and money than adding more optical cables. Selecting the right BiDi modules should not only consider the data rate, transmission distance, package form factors, and wavelengths, price and quality are also essential factors. If quality and price are your priorities, then FS.COM is the right place to be. Kindly contact or visit Fiber Optic Transceiver page of FS.COM for more details.

How to Connect 40G QSFP+ SR4 Transceivers to Network

40G network is gradually being applied in today’s backbone transmission network, during which long distance transmission is required. 40G QSFP+ SR4 fiber optic transceiver is being widely applied for 40G transmission in short distances. Generally, 40G QSFP+ SR4, working on wavelength of 850 nm, can support 40G fiber optic transmission a distance up to 150 m over OM4 multimode optical fiber. Inserted in switch, QSFP+ SR4 module utilizes a MTP/MPO interface for dual way transmission. There are a lot of methods to connect QSFP+ SR4 transceivers with other devices for different applications, by using different connectivity products. In addition, the cabling for 40G is relatively more difficult than that of 10G network, which requires more cables and spaces. The following will introduce several high density QSFP+ SR4 transceiver cabling methods.

QSFP+ SR4 40G to 40G Applications

40G to 40G transmission is needed in a 40G fiber optic network. The following picture simply illustrates how 40G to 40G multimode transmission is being achieved by QSFP+ SR4 transceivers. Two QSFP+ SR4 modules are separately inserted in two 40G switches. Then the two transceiver are connected by a length of multimode MTP trunk cable. This is the simplest way to use QSFP+ SR4 transceiver.

40G cabling

In some cases, there are lot of 40G connections required at the same time and same places, which means the increasing of both cable count and cabling difficulty. For better cable management and higher density cabling, a 48-port 1U rack mount MTP fiber patch enclosure can be used as shown in the following picture. Up to four 12-port MTP fiber adapter panels can be deployed in this standard 1U rack mount enclosure. With the help of this 48-port MTP fiber enclosure, cable management for 40G connections could be easier.

40G to 40G cabling

QSFP+ SR4 40G to 10G Applications

QSFP+ SR4 is a parallel fiber optic transceiver which means it uses four fibers for transmitting and four fibers for receiving at the same time. The 40G fiber optic signal can be separated into four 10G signals to meet the 40G to 10G transferring requirements. The fiber optic cable count will be increased at the 10G distribution end. Usually a breakout MTP-8LC harness cable is used. For better cable management, a 1U 96-fiber enclosure is recommended, which includes four HD MTP cassettes transferring MTP front the 40G end to LC at the 10G end. Four 10G-SR SFP+ modules, inserted in 10G switch/ports, can be connected to the corresponding LC ports on this fiber enclosure to achieve the duplex transmission between 40G and 10G.

40G to 10G cabling

For higher cabling density, the above mentioned 48-port 1U rack mount MTP fiber patch enclosure is still being recommended, which can provide high density 40G MTP cabling environment. And additional MTP-8LC harness cables should be used for transferring signals between 40G and 10G (shown in the following picture).

40G to 10G high density cabling


Depending on its parallel transmission mode, QSFP+ SR4 modules can meet a variety of cabling applications with great flexibility. The above methods is just several commonly used ones, detailed cabling methods for QSFP+ SR4 modules are depended on the practical applications and cabling environments. Related products for the above mentioned methods are listed in the following tables. Kindly visit FS.COM or click the attached links for more details. You can also contact for more information about 40G cabling.

Products Description
40G QSFP+ SR4 Module 40GBASE-SR4 QSFP+ 850nm 150m MTP/MPO DOM Transceiver
10G-SR SFP+ Module 10GBASE-SR SFP+, 850nm 300m, MMF, LC duplex
MTP Trunk Cable 12 Fibers OM4, 12 Strands MTP Female to Female, Polarity Type B
MTP-LC Harness Cable 8 Fibers OM4, 12 Strands MTP Harness Cable, Polarity Type B
LC-LC Fiber Patch Cable 1~100M LC-LC Duplex 10G OM4, MMF Fiber Patch Cable
96 Fibers Rackmount Fiber Enclosure 96 Fibers 1U Rackmount Fiber Enclosure loaded with 4 MTP HD Cassettes 2x MTP-12 to Duplex LC/UPC 10G OM4
48 Ports MTP Fiber Enclosure 1U Rackmount FHD Series Fiber Enclosure, Loaded with 4 FAPs (12xMTP)