With the rapid development of the network, the data center has been requesting for high bandwidth, reliability and low latency, as well as low cost high-speed interconnect solutions. In short distance data transmission, DAC high-speed cables have the advantages of low power consumption, low cost, and ease of use when compared to the combined solution of optical modules and fiber optic patch cables, so DAC cables are widely used in data centers.
The advantages of DAC high-speed cables
- Energy saving and environmental protection: the copper wire used in the internal material of the DAC high-speed cable, and the copper has a good heat dissipation, which is more energy-saving and environmentally friendly.
- Low power consumption: The power consumption of high-speed DAC cables is low. Generally speaking, the power consumption of optical modules is above 1W, but the power consumption of DAC high-speed cables is generally less than 0.5W.
- Low cost: The optical device of DAC high-speed cable does not have optical lasers and other electronic components, which can effectively save manufacturing costs, and the price of copper cable is much lower than that of optical fiber. For example, two interconnected 100G Cisco switches with a transmission distance of 1 meter. If you use a DAC high-speed cable, you only need a 1 meter 100G DAC high-speed cable, the price is 50usd; if you use an optical module + fiber optic patch cords, you need Two 100G SR4 optical modules and a 1-meter 12-core MTP fiber patch cord, the price of a 100G SR4 optical module is 120usd, a 1-meter 12-core MTP fiber optic patch cord is 30usd, so the total price is 270usd .
DAC high-speed cable structure
The DAC high-speed cable is composed of a cable and two optical connectors.
The cable uses silver-plated copper conductor, insulated by physical foamed HDPE, each pair shielding + total shielding, with high mechanical strength and insulation adhesion, and excellent signal return loss and little delay and anti-interference. The cable structure is mainly divided into four layers:
1. The first layer, each twisted pair wires, is mainly to combine the two HDPE insulated wires and one drain wire , and the outside is wrapped with an aluminum foil layer;
2. The second layer, 4 first layers wrapped with an aluminum foil later;
3. The third layer, is the layer of AL-Mg braid wrap the second layer, which is used to enhance the shielding effect of the wire and obtain better performance；
4. The fourth layer, the outer jacket is made of PVC.
In addition, DAC high-speed cables are divided into active DAC high-speed cables and passive DAC high-speed cables. The difference between these two is that the active DAC high-speed cables have an additional driver chip. At the same time, passive optical cables do not require power skills to show their Characteristics, and active optical cables require external power to display the characteristics. In general, when the transmission distance exceeds 5 meters, in order to reduce the signal interference problem, it is most appropriate to select an active DAC high-speed cable.
Application of DAC high-speed cable in data center
DAC high-speed cables can be divided into 10G SFP+ DAC high-speed cables, 25G SFP28 DAC high-speed cables, 40G QSFP+ DAC high-speed cables, and 100G QSFP28 DAC high-speed cables according to the transmission rate. They are mainly used for short-distance direct connection in data centers . At the same time, in order to meet the needs of users’ network upgrades, DAC high-speed cables, 40G QSFP+ DAC high-speed cables and 100G QSFP28 DAC high-speed cables are equipped with branch cable packages, which can be used for 40G-4*10G, 100G-4*25G In the network upgrade.
10G SFP+ DAC high-speed cables
10G SFP+ DAC high-speed cables are widely used in the interconnection between 10G fiber network cards, the interconnection between 10G ToR switches and servers, and the stacking of 10G Ethernet switches.
The 10G SFP+ DAC high-speed cable is based on a multi-source protocol of a pluggable small package optical transceiver module. It uses copper high-speed cables with SFP+ connectors at both ends, which can be used to connect devices (such as servers, fiber network cards, switches, etc.) with SFP+, and provides 10 Gigabit Ethernet connection. In the past, server motherboards use RJ45 ports or SFP ports. Now, with the development of big data and high bandwidth, 10G has begun to widely used on servers.
25G SFP28 DAC high-speed cables
25G SFP28 DAC high-speed cables are widely used in the interconnection of 25G equipment (such as servers, 25G fiber network cards, etc.) and supercomputers.
25G SFP28 DAC high-speed cable follows the IEEE P802.3by Ethernet standard and can provide users with 25G high-bandwidth data interconnection capabilities. Due to the late birth of 25G Ethernet, and the application of related optical communication products have not been popularized. But with the advent of the 5G network, the demand for 25G in the 5G prequel will bring a substantial increase.
40G QSFP+ DAC high-speed cables
As a direct connecting cable between 40G switches, 40G QSFP+ DAC high-speed cable has a compact and independent 4-channel pluggable interface and it is backward compatible with 25G and 10G. It is suitable for stacking and cascading between 40G devices. In order to meet more connection needs of users, 40G QSFP+ to 4*SFP+ DAC high-speed cables and 40G QSFP+ to 4*XFP DAC high-speed cables came into being, realizing network upgrades from 10G to 40G devices.
As the server port rate is upgraded from 1Gbps to 10Gbps, in order to achieve the basis of the network’s non-blocking full line rate, the uplink from the access layer to the core layer has been upgraded to 40Gbps/100Gbps, because the cost of the 40G fiber link is more cheap when compare with 100G, so most mid-sized companies will choose 40G when building data centers.
100G QSFP28 DAC high-speed cables
100G QSFP28 DAC high-speed cable has two types of interfaces: QSFP28 to QSFP28 and QSFP28 to 4*SFP28. 100G QSFP28 to 4*QSFP28 DAC high-speed cable is suitable for stacking, cascading and direct connection between short-distance 100G devices. Such as 100G switches, etc.; QSFP28 to 4*SFP28 DAC high-speed cable is suitable for the interconnection between 100G and 25G equipment.
With the rapid growth of Internet data usage, video on demand (VOD) and sharing etc. new high-bandwidth application. In order to meet higher bandwidth requirements and greater network capacity, large data centers are on the development towards 100G servers, the stack between switches has been upgraded from 10Gbps to 100Gbps.
DAC high-speed cable connecting solution in racks
DAC high-speed cables are generally used for short-distance direct connection between data center racks, with a length of 1 to 7 meters, the Max length is up to 12 meters. If the distances within 12-30 meters, you can choose AOC active optical cable, and if for long distances above 30 meters, you can choose optical module + fiber optic patch cords combination.
If your cabling scenario belongs to short-distance transmission, from the cost thinking, DAC high-speed cable is a good choice.