Tag Archives: QSFP+ cable

Do You Use QSFP+ Direct-Attach Twinax Copper Cable?


To achieve a 40G network connection, we usually use QSFP+ transceiver modules and MTP patch cords, which can help transmit 150 m to 40 km. But, if we only need to connect within 10 m, we can use QSFP+ direct-attach twinax copper cables. It’s a high-speed, cost-effective alternative to QSFP+ fiber optics. What’s QSFP+ direct-attach copper (DAC)? Whether should I use it? This blog will introduce the knowledge of QSFP+ DAC to you.

What Is QSFP+ Direct-Attach Twinax Copper Cable?
QSFP+ DAC is also called QSFP+ to QSFP+ cable. It has a QSFP+ module at one end and another QSFP+ module at the other end, and uses integrated duplex serial data links for bidirectional communication. Used to connect the 40 Gbps QSFP+ port of a switch at one end to another QSFP+ port of a switch at the other end, it can provide high quality of 40G end-to-end connection. Usually, maximum transmission distance of QSFP+ DAC is 10 m, which makes these cables are suitable for in-rack connections between servers and Top-of-Rack (ToR) switches. Besides, since its price ($30-$200) is much lower than QSFP+ optics, it’s a more cost-effective option to connect within racks and across adjacent racks.


Passive vs Active QSFP+ DAC
QSFP+ direct-attach twinax copper cable comes in either an active or passive twinax (twinaxial) and connects directly into a QSFP+ housing. An active twinax cable has active electronic components in the QSFP+ housing to improve the signal quality. A passive twinax cable is mainly just a straight “wire” and contains few components. Generally, twinax cables shorter than 5 meters are passive and those longer than 5 meters are active, but this may vary from vendor to vendor. QSFP+ direct-attach copper is a popular choice for 40G Ethernet reaches up to 10 m due to low latency and low cost.

Popular QSFP+ Cable Overview
At present, major QSFP+ DAC vendors are Brocade, Arista and Cisco. We can use QSFP+ DAC in their hardware with QSFP+ interfaces. Although the transmission distance of QSFP+ DAC can reach 10 m, the most common types we use are 1 m, 3 m, and 5m. In the market, popular QSFP+ DAC includes Brocade 1m(40G-QSFP-C-0101) , 3m(40G-QSFP-C-0301) and 5m(40G-QSFP-C-0501) passive QSFP+ twinax copper, Arista 1m(CAB-Q-Q-1M) and 3m(CAB-Q-Q-3M) passive QSFP+ twinax copper, and Cisco 1m(QSFP-H40G-CU1M) and 3m(QSFP-H40G-CU3M) passive QSFP+ twinax copper.

Brocade,Arista and Cisco DAC

40 Gbps Direct-Attached QSFP+ to QSFP+ Copper Cables (1 m, 3 m, 5 m) are optimized to fully leverage 40 Gigabit Ethernet (GbE) switches and routers. FS.COM provides a wide range of QSFP+ cable assembly options for your network connection, which satisfies the need for ultra-thin, light-weight, highly flexible cabling solutions for use in high density intra-rack applications.

Related Article: 40G QSFP+ Direct Attach Copper Cabling

How to Convert a Port From QSFP+ to SFP+?


As data communications technology migrates from 10GbE to 40GbE and beyond, it is often necessary to connect 40GbE equipment with existing 10GbE equipment. As we know 40GbE NIC or switch usually equipped with QSFP+ ports, and 10GbE switch usually equipped with SFP+ ports. That is to say we must know how to convert a QSFP+ port to a SFP+ port. At present, there exists three ways to solve this problem. I will explain it in this blog.

QSFP+ to SFP+ Cable
As shown in the figure below, a QSFP+ to SFP+ cable consists of a QSFP+ transceiver on one end and four SFP+ transceivers on the other end. The QSFP+ transceiver connects directly into the QSFP+ access port on the switch. The cables use high-performance integrated duplex serial data links for bidirectional communication on four links simultaneously. The SFP+ links are designed for data rates up to 10 Gbps each. QSFP+ cable is available in passive and active two types. Passive QSFP+ cable has no signal amplification built into the cable assembly, therefore, their transmission distance is usually shorter than an active one.


CVR-QSFP-SFP10G: QSFP+ to SFP+ Adapter (QSA)
You can convert a QSFP+ port to a SFP+ port using the QSFP+ to SFP+ adapter. QSA provides smooth connectivity between devices that use 40G QSFP+ ports and 10G SFP+ ports. Using this adapter, you can effectively use a QSFP+ module to connect to a lower-end switch or server that uses a SFP+ based module. This adapter is very easy to use. As shown in the figure below, just plug one side of the QSA in your QSFP+ port, and plug a SFP+ module into another side of the QSA. Then you can convert a QSFP+ port to a SFP+ port easily.


QSFP+ Breakout Cable
As we know, parallel 40GBASE-SR4 QSFP+ modules use 8 out of 12 MPO/MTP interface fibers transmitting 4 x duplex (DX) channels (4 x transmit and 4 x receive). The QSFP+ breakout cable uses a pinless MTP connector on one end for interfacing with the QSFP port on the switch. The other end contains 4 duplex LC connectors, which provide connectivity to the SFP+ ports on the switch. Thus higher-speed equipment (40G QSFP+) can be connected to slower-speed equipment (10G SFP+) successfully.

QSFP+ Breakout Cable convert qsfp+ to sfp+

When you want to connect a QSFP+ port to a SFP+ port, you can use QSFP+ to SFP+ cable, QSFP+ to SFP+ adapter or QSFP+ breakout cable. All these three options can meet your needs. FS.COM provides a full range of compatible QSFP+ cable, which can be 100% compatible with your Cisco, Juniper, Arista and Brocade switches and routers. Or you want to use QSFP+ breakout cable, you can also find it in our Fiberstore.

Related Article: 10G SFP+ and 40G QSFP+ Transceivers Cabling Solutions