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40GbE Parallel QSFP+ vs Duplex QSFP+ in 40G MMF Cabling

40GbE Parallel QSFP+ vs Duplex QSFP+ in 40G MMF Cabling

There two ways to deploy 40GbE multimode fiber (MMF) infrastructure. One is using the parallel transceivers with 12-fiber MTP cables. And the other one is to use the duplex transceivers with LC duplex cables (view transceiver options for 40GbE over duplex LC MMF cable). The former solution requires to add additional fiber to increase the number of 40GbE links. Thus, more fiber cost is taken in this solution. Conversely, the duplex transceiver solution allows for zero-cost fiber migration by reusing the current 10GbE fiber infrastructure for 40GbE connectivity. In this post, the typical cost difference for fiber infrastructure for parallel transceivers and duplex transceiver is introduced.

Typical MMF Cabling Cost Per 40GbE Link With Parallel Transceivers

In this scheme, a pairs of 40GbE parallel transceivers called 40GBASE-SR4 QSFP+ are used with the MTP patch cables and trunks. In addition, two MTP-MTP conversion modules are required. As shown in the picture below, there are two patch cables, two MTP-MTP conversion modules, and a 24-fiber trunk per link. Since the QSFP-40G-SR4 just uses 8 fibers in the trunk per link, total two MTP-MTP conversion modules can be used for 3 links.

40G parallel transceivers

The detailed cost for per 40GbE link with parallel transceivers are shown in the following table:

Item Unit Price Extended Price Per 40GbE Link
MTP patch cables (5 m, OM3) US$48.00 US$96.00
MTP-MTP conversion modules (OM3) US$400.00 US$267.00
24-fiber MTP trunk (90 m, OM3) US$367.00 US$123.00
Total US$486.00


Typical MMF Cabling Cost Per 40GbE Link With Duplex Transceivers

In the scheme using duplex transceivers, such as Juniper JNP-QSFP-40G-LX4 or Arista 40G QSFP-UNIV, two LC patch cables, two MTP-LC cassettes and a 24-fiber MTP trunks are used. As shown in the picture below, by deploying the duplex 40GbE transceivers, users can increase the number of 40G links by 4X without making any changes to their fiber infrastructure. In other word, the total two MTP-LC cassettes can be used for 12 links.

40G duplex transceivers

The detailed cost for per 40GbE link with duplex transceivers are shown in the following table:

Item Unit Price Extended Price Per 40GbE Link
Duplex LC patch cables (5 m, OM3) US$4.00 US$8.00
MTP-LC cassettes (OM3) US$120.00 US$20.00
24-fiber MTP trunk (90 m, OM3) US$367.00 US$30.00
Total US$58.00



The prices of product above are estimated according to FS.COM list prices (for reference only). Assume shipping costs are the same, as you see, a saving of over 90% on the cabling equipment alone is realized from the duplex transceivers. The project management costs to upgrade existing duplex systems are entirely avoided resulting in even more significant savings. In addition, the duplex transceivers mentioned above can also support running over single-mode fiber which is a cost-effective solution for migrating from multimode to single-mode fiber.

However, it is noted that the duplex 40GbE multimode transceiver is more expensive than the parallel one. For example, the 40GBASE-SR4 costs just 65 dollors while the LX4 costs about 400 dollors at FS.COM. Thus, the best option is just to choose the one you need, based on your network plan and future-proof upgrade.

Buyer Guides: At FS.COM, you can buy the above products at very affordable prices. In addition, you can buy both parallel and duplex 40GbE transceivers for many major brands compatible. For more information, please contact
How to Choose 40G QSFP+ Modules for Multimode Applications?

How to Choose 40G QSFP+ Modules for Multimode Applications?

cisco nexus 9396px switch with QSFP-40G-SR4

With the popularity of 40G QSFP+ modules in datacom industry, there are more alternatives for choose to replace the traditional 40GBASE-SR4 QSFP+ modules for multimode applications. To choose the most proper 40G QSFP+ modules for your applications not only offers the high performance but also saves more cost in the project.

Types of 40G Multimode QSFP+ Modules

Currently, there are three kinds of multimode 40G QSFP+ modules available in the market. They are:

Type Wavelength Distance Connector Type
40GBASE-SR4 QSFP+ 850 nm 150 m (OM4)
100 m (OM3)
40GBASE-CSR4 QSFP+ 850 nm 400 m (OM4)
300 m (OM3)
40GBASE-SR Bi-Directional QSFP+ 832 nm – 918 nm, BiDi 150 m (OM4)100 m (OM3)30 m (OM2) LC

So, which one is the best for you? In the following sections, several factors should be considered.

Distance Consideration

The maximum transfer distance of QSFP+ modules refers to how long distance can the module support to transmit. It usually depends on the transmission distance that your project is required. In general, 40GBASE-SR4 QSFP+ module can support up to 100 meters over OM3 multimode fiber and 150 meters over OM4 multimode fiber. In other word, if your expected transmission distance is under 150 meters, you can choose 40GBASE-SR4 QSFP+ module with OM4 fiber cable. If you have a longer distance requirement, the 40GBASE-CSR4 will be better for you since it can support up to 400 meters over OM4 multimode fiber.

Cabling Consideration

Generally, current multi-mode optics standards for 40GbE use parallel technology, namely using multiple 10Gbps lasers, simultaneously transmitting across multiple fiber strands to achieve high data rates (4 x 10 Gbps). Because of this, 40G optics use MPO or MTP cabling instead of the traditional duplex LC cabling. The most commonly used MPO/MTP cable presents 12 separate strands of multi-mode fiber in a single ribbon cable. 40G multimode QSFP+ modules with MPO/MTP interface include 40GBASE-SR4 and 40GBASE-CSR4. However, if you deploy the 40 GbE over the existing 10GbE infrastructure, the former two kinds of 40G modules are not applicable. In this case, you may choose the 40G BiDi QSFP+ module which can support up to 150 meters over OM4 multimode duplex LC cabling.

Other Considerations

In addition to distance and cabling considerations, other considerations such as compatibility, receiver sensibility, temperature and so on are also important. Users should have a proper plan of the network and choose the proper parameters depending on the requirements.

Compatibility Test of FS.COM 40GBASE-SR4 QSFP+ Transceiver on Cisco Nexus 9396PX Switch


40G QSFP+ modules are key components for 40GbE deployment. To choose the proper and cheap 40G QSFP+ can benefit the whole project. I will recommend you to visit FS.COM. They have a wide range options of 40G QSFP+ modules with very affordable prices. They may be an ideal choice for you.

Optics Use Cases for 40 Gigabit Ethernet Connectivity

Optics Use Cases for 40 Gigabit Ethernet Connectivity

The 40 Gigabit Ethernet (GbE), used in today’s networks as the preferred spine uplink technology, has become commonplace in data centers. With the rise of 40GbE QSFP+ optics market, various of optics solutions are available, which offer users a lot of flexibility in connectivity. Today, I am going to summarize some 40 Gigabit fiber optic connection use cases of several types of commonly used 40GbE QSFP+ optics.

Case One: QSFP+ to QSFP+ Direct Connectivity

For 40GbE to 40GbE connectivity, namely the interconnection between two QSFP+ ports, users can use different optics and cables options according to different transmission distances.

40GbE direct connectivity

  • For distances of up to 7 meters: QSFP+ to QSFP+ DAC (Direct Attach Copper) cables
  • For distances of up to 100 meters: QSFP+ to QSFP+ AOC (Active Optical Cable) or 40GBASE-SR4 QSFP+ transceiver with OM3 multimode fiber with MTP/MPO connectors or OM4 multimode fiber with MTP/MPO connectors (up to 150 meters)
  • For distances of up to 300 meters: 40GBASE-CSR4 QSFP+ transceiver with OM3 multimode fiber with MTP/MPO connectors or OM4 multimode fiber with MTP/MPO connectors (or up to 400 meters)
  • For distances of up to 1 kilometers: 40GBASE-PLRL4 QSFP+ transceiver can be used with single-mode fiber with MTP/MPO connectors
  • For distances of up to 10 kilometers: 40GBASE-LR4 QSFP+ transceiver can be used with single-mode fiber with LC connectors

Tips: The standard QSFP+ MTP/MPO connector is 12-fiber connector, but use 8 out of 12 fibers.

Case Two: 40GbE to 10GbE Ports Breakout

As we know, 40GbE ports can be used either as a single port or turned into four 10GbE ports. Thus, you can use so-called QSFP+ breakout or fan-out cables with QSFP+ on one side and four SFP+ on the other side to increase the number of available 10GbE ports.

In general, according to different distance requirements, the basic three types of solutions are available:

40GbE breakout connectivity

  • For distance of up to 5 meters: QSFP+ to SFP+ DAC Breakout Cables
  • For distance of up to 100 meters: QSFP+ Breakout AOCs
  • For distance of up to 300 meters: MTP/MPO to 4xLC Duplex OM3/OM4 multimode fiber breakout cables (mpo to lc duplex breakout cable) with the 40GBASE-CSR4 transceiver

Tips: When connect to networking switches or to server adapters which support SFP+ fiber optic connectivity, the QSFP+ DAC breakout cables are always the preferred option.

Case Three: Deploy 40GbE With Existing 10GbE Cabling Using LC Connectors

In today’s server networks, 10GbE has become commonplace. 10GbE multimode cabling with LC duplex connectors is the main infrastructure of 10GbE network. To leverage existing 10GbE cabling using LC connectors, the 40GBASE-SR QSFP+ Bi-Directional (BiDi) transceiver is an ideal choice for you. Used with WDM (Wavelength Division Multiplexing) technology, the 40GBASE-SR QSFP+ BiDi transceiver can support up to 100 meters with OM3 multimode fiber and up to 150 meters with OM4 multimode fiber cables with LC duplex connectors, allowing reuse of existing 10-Gbps fiber infrastructure for 40-Gbps connections so that helps reduce overall costs and installation time.

40GbE bidi


According to the above contents, we learned that the optics market for 40GbE connectivity is now relatively mature. Users can choose the most proper solution according to their network plan, requirements, and budget.

Use 40G BiDi QSFP+ to Transmit Over DLC MMF Cabling

Use 40G BiDi QSFP+ to Transmit Over DLC MMF Cabling

40G BiDi QSFP+As we know, the most commonly used solution for 40GbE multimode application is based on the interface standard QSFP-40G-SR4, which is running over multimode fiber (MMF) pre-terminated with 8-fiber MPO/MTP connectors. This causes a problem of fiber waste of the existing 10GbE infrastructure. So, how to reuse the exsiting 10GbE LC MMF cabling to achieve 40GbE network? The 40G BiDi QSFP+ transceiver may be an ideal choice for this requirement.

Today’s data centers are architected around 10 GbE, primarily focusing on 10GBASE-SR using duplex MMF with LC connectors. Data center operators want to upgrade from 10G to 40/100G without touching the duplex MMF infrastructure. This is becoming one of the data center interconnect trends. In order to meet this demand, the 40GbE BiDi QSFP+ transceiver has launched to the market. It offers users an option to run 40 GbE over duplex MMF with LC connector.

How can 40GbE BiDi QSFP+ transceiver do this? Now, turn to its working principle. As we know, 40GBASE-SR4 QSFP+ optics use independent lanes for transmit and receive (4 x Tx and 4 x Rx). The data rate of each lane is 10 Gbps. Thus, 8-fiber strands (8-fiber MPO/MTP) are required for using this optics. But for 40GbE BiDi QSFP+, as shown in the picture below, only two lanes are required, for each of 20Gbps. Each transmitted and received simultaneously on two wavelengths over a single MMF, enabling an aggregated 40Gbps link over a two-strand multimode fiber connection.

40GBASE SR4 QSFP+40GBASE-SR4 QSFP+ Working Principle

40GbE BiDi QSFP+40GbE BiDi QSFP+ Working Principle

Obviously, 40GbE BiDi QSFP+ transceiver has the absolute superiority on using the duplex MMF. However, some users may care the cost since that the cost of a 40GbE BiDi QSFP+ transceiver is much expensive than a 40GBASE-SR4 QSFP+ optics. But on the whole cost, you may find that the 40GbE BiDi QSFP+ is more cost-effective. Because you can save more on the fiber cost since the cost of fiber optic cables is also a big spending in your whole project.

Optics Channel Data Rate per Channel Fiber Type Price
40GBASE-SR4 QSFP+ 4 10 Gbps 8-fiber MPO/MTP MMF US$ 65.00
40GbE BiDi QSFP+ 2 20 Gbps Duplex LC MMF US$ 300.00

If you are still finding a way that can offer maximum reutilization of existing 10GbE fiber plant on 40/100G, help you achieve the 40GbE migration in a more cost-effective manner, the 40GbE BiDi QSFP+ transceiver may be your preferred choice. And in FS.COM, you can always find the high-performance transceivers in the most competitive price.




The QSFP+ transceiver is the dominant transceiver form factor used for 40GbE (Gigabit Ethernet) applications. In 2010 the IEEE standard 802.3ba released several 40GbE standard and along with the general specification, defined a number of fiber optic interfaces. These standard interfaces including 40GBASE-SR4 (QSFP SR4) and 40GBASE-LR4 (QSFP LR4) attempted to satisfy a number of different objectives including support for MMF (multimode fiber) and SMF (single-mode fiber) compatibility.

The basic versions of QSFP are SR4 and LR4 that are respectively designed for MMF and SMF 40GbE applications. SR is short for short reach and LR represents Long Reach. 4 means 4 Tx and Rx. The interfaces designed by 40GBASE-SR4 and 40GBASE-LR4 are not the same. The most obvious difference is that 40GBASE-SR4 is with MPO/MTP port while the 40GBASE-LR4 is with the Duplex LC port. The following table summarizes the differences between QSFP+ transceiver optical interfaces and electrical interfaces.


The cost of 40GBASE-SR4 QSFP+ is more cheaper than the 40GBASE-LR4 QSFP+. Additionally, the fiber cost of the cabling with them also have a big difference. Because smf cabling is more expensive than the mmf cabling.

With the wide deployment of 40 GbE, the 40GBASE-SR4 and 40GBASE-LR4 transceivers are more and more widely used. 40GBASE-LR4 QSFP+ transceivers (such as QSFP-40G-LR4) are most commonly deployed between data-center or IXP (Internet exchange point) sites with single-mode fiber. 40G SR4 QSFP+ transceivers (e.g. Cisco QSFP-40G-SR4) are used in data centers to interconnect two Ethernet switches with 8 fiber parallel OM3/OM4 multimode fiber cabling.