40G Solutions: Duplex Fiber or MPO/MTP Fiber?

There’s been a lot of talk lately surrounding bidirectional 40 Gb/s duplex applications, or BiDi for short. Currently offered as a solution by Cisco®, BiDi runs over duplex OM3 or OM4 multimode fiber using QSFP modules and wavelength division multiplexing (WDM) technology. It features two 20 Gb/s channels, each transmitting and receiving simultaneously over two wavelengths on a single fiber strand – one direction transmitting in the 832 to 868 nanometer (nm) wavelength range and the other receiving in the 882 to 918 nm wavelength range. Avago Technologies also offers a similar QSFP BiDi transceiver.

Unidirectional 40 Gb/s duplex fiber solutions are available from Arista and Juniper. These differ from the BiDi solution in that they combine four 10 Gb/s channels at different wavelengths – 1270, 1290, 1310, and 1330 nm – over a duplex LC connector using OM3 or OM4 multimode or singlemode fiber. These unidirectional solutions are not interoperable with BiDi solutions because they use different WDM technology and operate within different wavelength ranges.

40G Solutions

While some of the transceivers used with these 40 Gb/s duplex fiber solutions are compliant with QSFP specifications and based on the IEEE 40GBASE- LR4 standard, there are currently no existing industry standards for 40 Gb/s duplex fiber applications using multiple wavelengths over multimode fiber – either bidirectional or unidirectional. There are standards-based 40 Gb/s applications over duplex singlemode fiber using WDM technology, but standards-based 40 Gb/s and 100 Gb/s applications over multimode use multi-fiber MPO/MTP connectors and parallel optics (40GBASE-SR4 and 100GBASE-SR4).

40 Gb/s duplex fiber solutions are promoted as offering reduced cost and installation time for quick migration to 40 Gb/s applications due to the ability to reuse the existing duplex 10 Gb/s fiber infrastructure for 40 Gb/s without having to implement MPO/MTP solutions. However, some of the concerns surrounding these non-standards based 40 Gb/s duplex fiber solutions include:

  • Lack of standards compliance and lack of interoperability with standards-based fiber solutions
  • Risk of being locked into a sole-sourced/proprietary solution that may have limited future support
  • BiDi and other 40 Gb/s duplex transceivers require significantly more power than standards-based solutions
  • Lack of application assurance due to operation outside of the optimal OM3/OM4 wavelength of 850 nm
  • Limited operating temperature range compared to standards-based solutions

Due to the aforementioned risks and limitations of using non-standards-based 40 Gb/s duplex fiber solutions, we recommends following industry standards and deploying 40GBASE-SR4 for 40 Gb/s applications today. While this standard requires multiple fibers using an MPO/MTP-based solution, it offers complete application assurance and interoperability, as well as overall lower power consumption.

Furthermore, TIA and IEC standards development is currently underway for wideband multimode fiber (WBMMF), which is expected to result in a new fiber type (potentially OM5 or OM4WB) that expands the capacity of multimode fiber over a wider range of wavelengths to support WDM technology. While not set in stone, the wavelengths being discussed within TIA working groups are 850, 880, 910, and 940 nm.

Unlike current 40 Gb/s duplex fiber applications, WBMMF will be a standards-based, interoperable technology that will be backwards compatible with existing OM4 fiber applications. WBMMF is expected to support unidirectional duplex 100 Gb/s fiber links using 25 Gb/s channels on 4 different wavelengths. WBMMF will also support 400 Gb/s using 25 Gb/s channels on 4 different wavelengths over 8 fibers, enabling existing MPO/MTP connectivity to be leveraged for seamless migration from current standards-based 40 Gb/s and 100 Gb/s applications to future standards-based 400 Gb/s applications.

40G QSFP+ Direct Attach Copper Cables

With the wide deployment of 40 Gigabit Ethernet, the 40G QSFP+ direct attach copper cables are becoming more and more popular due to the compact size, low power and cost-effectiveness. 40G QSFP+ to QSFP+ direct attach copper cables and 40G QSFP+ to 4 x 10G SFP+ direct attach cables are hot pluggable and parallel passive/active copper cables for storage, data, and high-performance computing connectivity.

QSFP+ to QSFP+ Direct Attach Cable

QSFP+ to QSFP+ direct attach copper cables are hot-removable and hot-insertable. A cable consists of a cable assembly that connects directly into two QSFP+ modules, one at each end of the cable. The cables use integrated duplex serial data links for bidirectional communication and are designed for data rates up to 40 Gbps. QSFP+ to QSFP+ direct attach copper cables are suitable for very short distances and offer a highly cost-effective way to establish a 40G link between QSFP+ ports of QSFP+ switches within racks and across adjacent racks. These cables connect to a 40G QSFP port of a switch on one end and to another 40G QSFP port of a switch on the other end.

direct attach cables-EX-QSFP-40GE-DAC-50CM

QSFP+ to 4 SFP+ Direct Attach Cables

The move from 10G to 40G Ethernet will be a gradual one. It is very likely that one may deploy switches that have 40G Ethernet ports while the servers still have 10G Ethernet ports. For that situation, we should use a QSFP+ to 4 SFP+ direct attach breakout copper cable. These cables connect to a 40G QSFP port of a switch on one end and to four 10G SFP+ ports of a switch on the other end, which allows a 40G Ethernet port to be used as four independent 10G ports thus providing increased density while permitting backward compatibility and a phased upgrade of equipment.


Directions for Use

The 40G QSFP+ direct attach cables are used to connect switch to switch or switch to server. When we use a fiber optic transceiver and patch cable to establish a fiber link, we should firstly plug the transceiver to the network switch and then plug the patch cable to the transceiver. But for a QSFP+ direct attach copper cable, both SFP+ connector and QSFP+ connector can be directly inserted into the switch and don’t need a transceiver at all, which provides a really cost-effective solution for interconnecting high speed 40G switches to existing 10G equipment or 40G switches to 40G switches.


40G QSFP+ direct attach cables can provide inexpensive and reliable 40G speed connections using copper cables with distances reaching up to 30ft (~10 meters length). Cost of short reach connectivity is significantly reduced by avoiding the more costly fiber transceivers and optical cables. As the main fiber optical manufacturer in China, FS provides a good selection of 40G QSFP+ copper cables, both passive and active copper cables are available. For longer distances, active copper or optical cables are required. For more information or quotation, please contact us via sales@fs.com.

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40G QSFP+ Direct Attach Copper Cable
Use High Speed Direct Attach Cable for Data Center Interconnection

Twisted-pair and Direct Attach Twinax Cables Will Become a Trend

Now fiber optic transceivers are commercially available for almost all international and industrial standards, including Ethernet, Fast Ethernet, Gigabit Ethernet, 10Gbit Ethernet. What’s take an important role in this situation is SFP fiber optic transceiver. So let’s take an eye on it. SFP is also called small form-factor pluggable which is a version of Mini GBIC. at first sight, you can find the size is only half of GBIC. It supports data rates up to 10 G. The SFP Transceiver are available with a variety of transmitter and receiver types. What’s more, it is with LC interface. The kind of SFP transceiver module called SFP-10G-SR in Fiberstore is a quite well choice, it is nearly same as Cisco SFP 10G SR. SFP is regarded as a hot pluggable module, this make it Effortless to alter and effortless for upkeep in comparison with conventional modules. It makes the Ethernet network easier to upgrade and sustain. End users can replace a Solitary SFP module Throughout the Procedure Rather of replace the complete board with various modules on it.

SFP+ Transceiver Module

SFP+ twinax cables are copper cables with two SFP+ transceivers attached on either end. This  SFP cable is also known as Direct Attach Cables (DAC). Using twinax cable is significantly cheaper than connecting devices using two 10 Gbps fiber optic transceivers over fiber cable. There are two types of twinax cables. active and passive. In IBM b-type switches only active cables are supported which contain Vital Product Data (VPD) information. Twinax cable is available in length of 1m, 3m, and 5m. Also referred to as twinax, a direct-attach twinaxial cable is very similar to coaxial cable, except for one additional copper conductor core. Both twinax cores are protected by an insulator layer and another metallic conductor surrounding the core pair. Analogous to twisted-pair cables, both cores are twirled together to diminish interference effects from outside sources.

Originally created by IBM for shorter-distance connections, twinax cables offer a cost effective way to interconnect Ethernet devices within racks and across adjacent racks. These cables are usually accommodated into the transceiver housing of a switch or server. Direct-attach 10 Gigabit Ethernet twinax cables have Enhanced small form factor pluggable (SFP+) compatible connectors while 40 Gigabit Ethernet twinax cables deploy Enhanced Quad small form factor pluggable (QSFP+) connectors.

On both data rates, twinax cables are available in the following types. Active: Have components in the SFP+ or QSFP+ housing to improve the signal quality. Usually covers 7 and 10 meters. Passive: Have straight conduction between devices and are available in 1, 3, and 5 meters. for example Cisco SFP-H10GB-CU1M and what SFP-H10GB-CU1M in Fiberstore has same functions with Cisco’s and it also fully compatible with Cisco devices, the same time the price is lower than Cisco’s. Twinax cables have achieved high popularity in data centers because of their high benefit/cost ratio. As an additional advantages, twinax cables present a much lower bit error rate (1 error in 10 E18 bits transmitted) than the IEEE requirements for 10 Gigabit Ethernet connections (1 error in 10E12 bits transmitted). Although the 2004 IEEE 802.3ak standard was the first to introduce 10 Gigabit Ethernet in Twinax cables (10 GBase-CX4), this superseded solution was based on infiniband twinax cables, The twinax cables currently used in 10 Gigabit Ethernet are standardized by the small form format committee standard SFF-8431 and 8461.

Although the Ethernet standardization process has its fair share of politics, the study of its timeline remains a good way to access the networking industry trends over the last three decades. we can see some trends, such as twisted-pair roughly increased ten times its data rate every five years. That pace, however, did not continue in speeds higher than 10 Gbps. Optical fiber had a slightly faster development, being the first media to support data rates higher than 100 Mbps. It also presented the highest longevity among all media. Twinax cables have risen as a viable Ethernet option for 10-Gbps connections.

Because of the higher cost of optical transceivers, fiber is typically employed on links between switches, where higher speeds are required the earliest. High-volume connections, such as server access, depend on lower costs to justify an upgrade to faster data rates. For that reason, twisted-pair and direct-attach twinax cables have been the most popular choices for these connections.

At last, The above information are come from Fiberstore fiber optic manufacturer. Go ahead to check out the details! And the same time there is a good news is that Fiberstore is making a 30% discount about most products, welcome you to visit our online store.