Tag Archives: QSFP-40G-SR4

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

How to Connect Cisco Nexus 9396PX to 40G Network

Both devices and network architecture should be considered during data center upgrade. With the driven of applications like Cloud, Internet of Things, and virtual data center, it is clear that 10G can no longer satisfy the application needs. Migrating to 40/100G is an urgent problem. Cisco Nexus 9396PX switch, as one of the first member of Cisco Nexus 9000 series platform, can support 40G transmission with flexibility and high density. However, the problem is that many customers do not know how to get there to make full use of these devices. This post will give a detailed description about how to connecting Cisco Nexus 9396PX switch to optimized network architecture.

spine-leaf architecture vs 3-tier architecture

Optimized Network Architecture—Spine-Leaf Architecture

The traditional network usually used a three tier network architecture. However, with the migration of 40/100G, a new architecture is taking place of the traditional one with great advantages. This is known as spine-leaf architecture. Compare with the traditional three tier network architecture, spine-leaf uses a two-tier mode as shown in the above picture. Several most obvious advantages of spine-leaf architecture are list as following:

  • spine-leaf network is more adaptable to the continuous change of data center. This is because an additional Spine switch may be added and uplinks may be extended to every Leaf switch, resulting in the addition of interlayer bandwidth and reduction of the oversubscription.
  • Spine-leaf network can create high density cabling environments depending on the scale of the network.
  • Using a two-tier mode, spine-leaf network can reduce the overall signal latency through the elimination of a switching layer.

Cisco Nexus 9396PX ports information

Connecting Cisco Nexus 9396PX to 40G Spine-Leaf Network

To make full use of the given source, spine-leaf architecture is suggested. As shown in the above picture, the Cisco Nexus 9396PX is a 2RU non-blocking Layer 2 and 3 fixed switch offering 48 ports of 1G SFP/10G SFP+ and 12 ports of 40G QSFP+. Cisco Nexus 9396PX switch is suggested to be used as the leaf switch in 40G spine-leaf network. Cisco Nexus 9396PX is suggested to be used as leaf switch in 40G spine-leaf network. In spine-leaf network architecture for 40G application, the connections between the spine switches and leaf switches are 40G, while connections between the leaf switches and servers are usually 1/10G. Thus these 40G QSFP+ ports can be used to connect the spine switch and the 1G SFP/10G SFP+ are suggested to connect servers and routers. To accomplish the whole spine-leaf connection, optics and cables or DAC (direct attach cable) should be used. The following picture shows a 40G spine-leaf architecture with Cisco Nexus 9396PX being used in the leaf layer and the fiber cabling choice for Cisco Nexus 9396PX switch in this architecture.

Cisco Nexus 9396PX spine-leaf connection solution

Cisco Nexus 9396PX Cabling Solution

Using the fixed switch Cisco Nexus 9396PX with spine-leaf architecture can greatly increase the network scaling capability and adaptability. Detailed information about modules and cables that can be used with Cisco Nexus 9396PX are listed in the following chart.

Connection Option 1: Optics & Cable Option 2: DAC
Spine to leaf
(40G connection)
QSFP-40G-SR4 MMF, OM3/OM4, MPO patch cable QSFP-H40G-AOC (1m to 10m are available)
QSFP-H40G-CU (1m to 5m are available)
QSFP-H40G-ACU (7m to 10m are available)
QSFP-40GE-LR4 SMF, LC duplex patch cable
Leaf to server
(1/10G connection)
SFP+ Optics SFP-10G-AOC (1m to 10m are available)
SFP-H10GB-CU (1m to 5m are available)
SFP-10G-SR MMF, LC duplex patch cable
SFP-10G-LR SMF, LC duplex patch cable
SFP Optics
GLC-T (1000BASE-T) RJ-45, Cat 5
GLC-SX-MMD MMF, LC duplex patch cable
GLC-LH-SMD SMF, LC duplex patch cable

All the products mention in this chart can be customized according to your applications in Fiberstore (FS.COM). They will be fully tested in Fiberstore Test Center before they go to the market. Kindly contact sales@fs.com for more details.