Mar 22


Due to the ever-increasing requirement for higher speed transmission, 40G Ethernet is introduced to networking world, and it will gradually dominates the market. Many vendors have released different kinds of devices to support 40GbE, among which 40G QSFP+ module is the most popular and available for short distance or long distance data transmission. There are two variants short distance QSFP+ modules: QSFP-40G-SR4, and QSFP-40G-UNIV, what are the differences among these two types? This passage will tell you and give more information.

Differences in Interfaces and Transmission Media

Commonly, for QSFP+ modules, there are mainly two connector interfaces: MPO/MTP and duplex LC(Note: LC interfaced QSFP+ uses serial transmission, while MPO/MTP interfaced QSFP+ uses parallel transmission. In serial transmission, bits are sent simultaneously on different channels within the same cable, and in parallel transmission, bits are sent sequentially on the same channel). QSFP-40G-SR4 uses MPO/MTP to achieve data transmission over multimode fiber. However, in order to avoid wasting cost and deployment time when installing in different cabling structure, duplex LC interfaced QSFP-40G-UNIV is designed to be used in both single-mode and multimode links without adding any hardware or software.

different interface between QSFP-40G-SR4 and QSFP-40G-UNIV

Differences in Working Principle

For MPO/MTP interfaced 40GBase-SR4, it offers 4 independent full-duplex transmit and receive channels, each capable of running up to 10G data rates per channel, achieving the total 40G data rates. These modules are often used with 12-fiber MTP trunk cable, four transmitting and four receiving, leaving the middle four unused. For duplex LC interfaced 40GBase-UNIV, it also uses four transmitters and four receivers but has built in optical multiplexing and de-multiplexing, which results in a duplex connector and hence operates over the same duplex fiber infrastructure as 10GBASE-SR.

different working principle of QSFP-40G-SR4 and QSFP-40G-UNIV

Differences in Transmission Distance

40GBase-SR4 module can support link lengths of 100 meters and 150 meters, respectively, on laser-optimized mutimode fibers, and it can also be used in a 4x10G mode interoperability with 10GBase-SR interfaces up to 100 and 150 meters on OM3 and OM4 fibers, respectively. 40GBase-UNIV can support the same transmission distance over OM3 and OM4 fibers, but it can also achieve link lengths of up to 500 meters over single-mode fiber.

Differences in Cost Consumption

40GBase-UNIV is much more expensive than 40GBase-SR4. Take FS.COM for example, 40GBase-UNIV is $340, while 40GBase-SR4 is $55. Besides the price of the unit itself, we should also take the whole deployment cost consumption into consideration. Migrating from 10G to 40G is inevitable. The existing 10G network uses two fibers for dual transmission. But most 40G network uses 12-fiber MTP based fiber optic cable for dual-way transmission over multimode fibers, which means if we use 40GBase-SR4 with MTP port for 10G to 40G migration, more optical fibers will be added and the cabling infrastructure will be changed. However, with 40GBase-UNIV module, it can support the same or longer transmission distance as the 40GBase-SR4 does, but it uses two strands of dual-way transmission like most 10G network, which will keep the existing 10G network when upgrade to 40G, greatly saving cost and time.

10G to 40G migration with QSFP-40G-SR4 and QSFP-40G-UNIV


We have introduced QSFP-40G-SR4 and QSFP-40G-UNIV modules for short distances transmission. These two module types have different features. Choosing which one totally depends on your practical applications and budgets. FS.COM has plenty of QSFP-40G-SR4 and QSFP-40G-UNIV optics in stock. For more information, please check FS.COM.

Mar 07

Can We Use Base-8 and Base-12 Together?

Although 10 Gigabit Ethernet is still marketing its way into the data centers, the need for faster data transfer rates is relentless, which means the migration to 40 Gigabit Ethernet is becoming inescapably compelling. For 40G Ethernet network, there are mainly two connectivity methods, one is Base-8, and the other is Base-12. Base-12 connectivity has had its place in the data center, while Base-8 is a new connectivity that could gain widespread acceptance in the next few years. With these two methods existing in 40G Ethernet network, there comes problems: Which one is more suitable for 40G network, or can we both use these two methods in 40G network? Read this articles, and you will get the detailed answers.

Base-12 Dominates the Market

Base-2 connectivity is the most commonly used one in the past, but as the data center grew to thousands of fiber ports engaged, stringing two-fiber patch cords across all corners of the data center will result in an unmanageable, and unreliable mess. So Base-12 connectivity is introduced. It is designed to develop a modular, high density, structured cabling system which could be deployed in data centers quickly, while also maximizing port densities within the rack space. In this connectivity method, all the fiber optic cables are based on an increment of 12 fiber, like 12-fiber or 24-fiber MTP trunk cable.

Base-12 system using a 24-fiber trunk cable

Base-8 Shines the Light

Base-12 connectivity is common in data center, but here comes a problem when installed it in a parallel system. For example, if we need to use 40GBase-SR4 optics implemented in a 12-fiber infrastructure, four fibers for transmit, and four fibers for receive, leaving four fibers unused per connection, this will lead to a significant and costly loss in fiber network utilization. But Base-8 can be a more cost-effective option for end-to-end MPO to MPO channels and architectures. With 8-fiber infrastructure, the 40GBase-SR4 module will use all the 8 fibers. Base-8 connectivity makes use of fiber links in increment of 8 versus 12. The 12-fiber trunk cables are replaced with trunk cables in increment of 8: 8-fiber, 16-fiber, or 24-fiber trunk cables, etc.

Base-8 system using a 24-fiber trunk cable

Can We Use Base-8 and Base-12 Together?

Although using Base-8 connectivity could decrease fiber consuming in supporting 40G data rates, in fact, in many cases, Base-8 connectivity isn’t a universal solution, and Base-12 may still be more cost-effective. So is it possible to have both Base-8 and Base-12 connectivity in the same data center? The answer could be “Yes” or “No”.

Base-8 and Base-12 Fiber Links Cannot Be Mixed and Matched

It is never possible to directly mix the components of Base-8 and Base-12 connectivity, or plug a Base-8 trunk into a 12-fiber module. Because a Base-12 trunk cable normally has unpinned MTP connector on both ends, and requires the use of pinned 12-fiber breakout modules, while a Base-8 trunk cable is manufactured with pinned MTP connectors at both ends (pinned and unpinned MTP connectors are shown below). So if we plug a Base-8 trunk into a 12-fiber breakout module, just like trying to mate two pinned connectors together, this connection will definitely not work, and vice verse.

pinned and unpinned MTP connector

Base-8 and Base-12 Can be Maintained in the Same Data Center Separately

It is possible to deploy both Base-8 and Base-12 connectivity within the same data center, just as long as the links are separate. Since Base-8 and Base-12 components are not interchangeable, during managing the data center physical layer infrastructure, we should do careful management and labeling practice to ensure we will not mix or mismatch them.


Base-12 connectivity has dominated the 40G network market for years, while the Base-8 connectivity is an additional option in the network designer’s tool kit to ensure that data centers have the most cost-effective, future-proof network available. When using Base-8 and Base-12 in network, make sure that you need to carefully manage and label them, and that the components in Base-8 and Base-12 won’t be mixed.