QSFP-40GE-LR4 and QSFP-40G-SR4 Modules Comparison

Have you ever complained about your slow network speed when you are working in a hurry, watching the most wonderful and interesting part of a movie or doing something else that are delayed by your bad network? Do you want to upgrade your system for higher data transmission speed? Have you ever heard about 40G QSFP+ module which is able to solve your problem? In this post, it will introduce two commonly used types of QSFP+ modules used to upgrade your network from 10G Ethernet to 40G Ethernet, to some extent, avoiding time delay.

40G QSFP+ Modules Overview

Nowadays, there are several solutions designed for deploying 40G Ethernet network, such as, 4 x 10GE Breakout cable, 40G QSFP+ modules or 40G CFP modules. Both of these solutions can achieve the 40GbE with higher capacity. As one of the most commonly used solutions among them, 40G QSFP+ module is a good choice to make the 40G migration. Do you have a good knowledge of 40G QSFP+ modules in the fiber market? At present, there are many variants of 40G QSFP+ modules published to support different applications, defined by IEEE 802.3ba. For instance, QSFP-40GE-LR4, QSFP-40G-PLR4, QSFP-40G-SR4, QSFP-40G-CSR4, etc.

Differences Between QSFP-40GE-LR4 and QSFP-40G-SR4

Among the variants of 40G QSFP+ modules, QSFP-40GE-LR4 and QSFP-40G-SR4 are the most widely applied modules that are designed for different aims. Their features are much different from each other, varying from fiber type to transmission distance. The following will basically analyze the differences between these two modules that may be useful for you to select a proper 40G QSFP+ module.

• Different Fiber Type

As for QSFP-40GE-LR4 module, it has four WDM lanes to transmit and receive signal, which generally works with single-mode fiber. With the advantage of single-mode fiber, it can transmit 40G signals with a long distance. As for QSFP-40G-SR4 module, it has four lanes, which enables high-bandwidth 40G optical links over 12-fiber multimode fiber, operating on a parallel mode. Although it can’t support long distance transmission like QSFP-40GE-LR4 module, it has the ability to carry many kinds of optical signals in 40G Ethernet network.

• Different Connector

As for the connector, QSFP-40GE-LR4 module always uses duplex LC connectors to connect single-mode fiber, while QSFP-40G-SR4 module is often terminated with MPO/MTP connector used for linking 12-fiber multimode fiber. What should pay attention to is that each kind of connector is easy to be smudged, which may cause a negative effect on the transceiver performance. Hence, no matter which module you choose to deploy 40G Ethernet network, please use a dust plug to protect the connector if the QSFP+ module is not working, so that the connector can be stay in a clean condition.

• Different Wavelengths

There is no doubt that the light wavelengths are also different used for transmitting signals. As for the former one, it generally uses signals with four different wavelengths, 1271 nm, 1291 nm, 1311 nm and 1331 nm to achieve 40G long distance data transmission. However, the latter one uses the same wavelengths for four lanes: 4 x 850 nm, supporting 40G short data transmission.

• Different Transmission Distance

It is easy to learn that the letter “L” in QSFP-40GE-LR4 refers to the word “long”, while the letter “S” in QSFP-40G-SR4 stands for “short”. Then how far these two QSFP+ modules can transmit 40G signals? What’s the difference? As for the former one, by using Coarse Wavelength Division Multiplexing technology, it transmit 40G signals through single-mode fiber with four separated or combined 10G SFP+ modules on the other end, with great reach of up to 10 kilometers. However, the latter one can only transmit 40G signals at lengths up to 100 meters on OM3. If it uses OM4 to support the 40G Ethernet network, it can transmit longer, 150 meters.

Conclusion

Have you got any useful information from the post for choosing a suitable QSFP+ module? As above mentioned, QSFP-40GE-LR4 designed with special features is most suitable for 40G long distance transmission, such as, between data-center or IXP sites. If you just need to deploy 40G Ethernet network for short distance, QSFP-40G-SR4 must be an ideal choice with lower price.

How Much Do You Know About 40G QSFP BiDi Transceiver?

As we know, there are a variety of QSFP transceivers that have the ability to support 40G Ethernet network with higher capacity and transmission data rate, such as: QSFP-40G-SR4, QSFP-40G-CSR4, QSFP-40G-LR4, QSFP-40G-PLR4, etc. In 40G long distance transmission, there is no doubt that OSFP+ transceivers with duplex LC interface like QSFP-40G-LR4 and QSFP-40G-PLR4 have a high performance. However, for 40G short distance transmission, both QSFP-40G-SR4 and QSFP-40G-CSR4 transceivers are designed complicatedly, requiring 12-fiber MTP/MPO connectors and 12 fibers, which are extremely different from the traditional 10G transceivers. Hence, the cabling infrastructure for the migration from 10G to 40G Ethernet network in short transmission should be changed greatly, which may cost a lot.

Taking the cost into consideration, experts come up with the BiDi technology and design QSFP bi-directional transceiver for 40G short transmission. By using QSFP BiDi technology, 40G Ethernet network can be deployed with the same infrastructure as 10G Ethernet network, thereby a cost saving will be made.

40G QSFP BiDi Transceiver Overview

40G QSFP BiDi transceiver can be also called 40G QSFP bi-directional transceiver, firstly published by Cisco. It is able to transmit 40G signals over duplex multimode fiber optic cables with LC connectors, instead of multi-fibers with MTP/MPO connectors in the traditional 40G QSFP parallel transceiver, which addresses the challenges of cabling infrastructure. In general, there are a pair of duplex MMF cables with duplex LC connectors in one 40G QSFP BiDi transceiver. Each cable offers a 20G channel to transmit and receive 20G signals simultaneously with different wavelengths, achieving a complete 40G data transmission. For better understanding, here offers its working principle in the following figure.

Cabling Connection Options for 40G QSFP BiDi Transceiver

When designing 40G Ethernet network with BiDi technology within a given row of cabinets, a Type A-to-B standard LC duplex patch cord is suggested to directly connect two 40G BiDi transceivers. As shown in the following figure, the Type A-to-B standard LC duplex patch cord consists of a blue fiber linked with connector position A on one side and connector position B on the opposite side, and an orange fiber linked in the same way, defined in TIA-568-C.3. This reverse fiber positioning allows a signal to be directed from the transmit position on one end of the network to the receive position on the other end of the network.

Interconnect Option for 40G QSFP BiDi Transceiver

How can an interconnect cabling be deployed for 40G BiDi transceiver? As shown in the following figure, we can learn an example of an interconnect link between two bidirectional ports installed in a switch, which includes an MTP-based trunk, MTP-LC cassette modules and LC jumpers. In this interconnect link, both of the LC jumpers connect from the structured cabling patch panel to the electronics ports.

There are a lot of advantages by using interconnect cabling for 40G QSFP BiDi transceiver. Firstly, MMF MTP assembly in this interconnect cabling would provide more scalability to accommodate future data rates. Secondly, if you want to do a migration for your network in future, it can be done simply by changing the patch panels on each end of the link, instead of disrupting the cabling infrastructure. What should be pay attention to is that deployment of more permanent links should be taken into consideration when structured cabling is being designing.

Cross-connect Option for 40G QSFP BiDi Transceiver

Other than interconnect cabling, there are two independent structured cabling links that connect two switches in a centralized cross-connect cabling. Here offers an example of the cross-connect cabling approach for 40G BiDi transceiver in the following figure for your reference.

This cross-connect cabling is featured with the most flexible network configuration. That is to say, the electronic devices can be installed in various locations throughout the data center, with structured cabling links between the cross-connect location and designated zone cabinets. If you want to install a new equipment in the link, you just need patch cords to make the connection from the equipment to the patch panels.

Conclusion

When making the migration from 10G to 40G Ethernet network in short distance transmission, 40G QSFP BiDi transceiver would be the first choice that requires no changes in the cabling infrastructure. Hence, the cost and required time to deploy 40G Ethernet network could be reduced dramatically. There is no doubt that 40G QSFP BiDi transceiver will eventually displace the traditional 40G QSFP transceiver in a fast and cost-efficient manner.