With the advantages of lower cost and easier installation, SFP+ cables are getting more and more popular for short-distance connectivity in 10G data transmission than 10G transceivers. This article offers a buying guide for 10G SFP+ cables from the aspects of types, benefits, applications and choosing tips.
SFP+ cable is a form of high-speed cable with SFP+ connector modules on either end. It uses the connector to transmit and receive 10Gbps data through one paired transmitters and receivers over a thin twinax cable or a fiber optic cable. They are suitable for in-rack connections between servers and switches, saving significant costs and power in short-reach applications. 10G SFP+ cables can be classified into 10G SFP+ DAC and 10G SFP+ AOC.
10G DAC, classified into passive DAC and active DAC, is made from twinax copper and is factory terminated with modules that provide an electrical connection directly into active equipment. The former can deliver without signal conditioning, while the latter has electric components inside the transceivers to boost signals. 10G SFP+ DAC cable is ideal for shorter top-of-rack or rack-to-rack runs with cost-conscious budgets.
10G AOC is an amalgamation of optical components and electronics or active electrical components, requiring external power to complete the conversion of signals. It uses a fiber cable and silicon chip and provides an electrical-to-optical connection to boost the signal and performance of the cable. 10G SFP+ AOC cable is generally used for end-of-row or middle-of-row data center architectures for interconnecting distances of up to 15m.
Figure 1: 10G SFP+ Cables
Cost: Without expensive electronic components, 10G SFP+ cable is much cheaper than 10G optical transceivers. And with a power consumption of lower than 0.15w, the operating expenses of passive DAC will be much fewer.
Convenience: It is more flexible and less difficult to adopt 10G SFP+ cables during the actual construction deployment. Just plug SFP+ cables into your physical equipment (such as network switch) directly, the connection is achieved without any additional signal processing or conversion.
10G SFP+ DAC and AOC are widely adopted in data centers to connect servers, storage appliances and switches. In general, these cables are particularly effective in the following two applications.
10G SFP+ DAC is usually applied for ToR (Top of Rack) interconnections between 10G ToR switch and server or the stacking of 10GbE switches. Since 10G SFP+DAC typically supports a link length of 7m with low power consumption, low latency and low cost, this option is an ideal choice for short-range server-to-switch connections.
Figure 2: 10G SFP+ DAC Cable: Server to Switch Connectivity
Without the strict link length limits, 10G SFP+ AOC is commonly used in several locations in the data center like ToR, EoR (End of Row) and MoR (Middle of Row). Therefore, 10G SFP+ AOC cable assemblies are high-performance and cost-effective I/O solutions for 10G Ethernet and 10G Fibre Channel applications. With the theoretical maximum reach up to 100m, 10G SFP+ AOC cables are often used in switch-to-switch connections.
Figure 3: 10G SFP+ AOC Cable: Switch to Switch Connectivity
Generally, there are four factors that should be taken into account before making the final decision: 10G AOC or 10G DAC.
10G AOC, using fiber optic cable as transmission media, has a much smaller size and lighter weight when compared with 10G DAC. So it can be flexibly deployed in places where space is strictly limited, and can be transported from one place to another. Also, the bending radius of 10G SFP+ AOC is significantly smaller than 10G SFP+ DAC, which makes 10G AOC cable more suitable for high-density cabling structures.
10G SFP+ DAC cable is a passive device with nearly no power consumption, which is much lower than that of 10G AOC cables, so it can reduce costs.
10G AOC can transmit distances up to 100m, while the max transmission distance of 10G DAC is 10m (passive DAC-7m; active DAC-10m). Therefore, 10G SFP+ DAC cables are suitable for short-range scenarios, and AOC solutions are applied in long-range networking cases. (Note: the max transmission distance of a signal on 10G DAC cable depends on the data rate. The link length will decrease as the data rate grows, for example, 100G DAC cables can only transmit up to 5m.)
Electromagnetic Interference (EMI), refers to a disturbance generated by an external source that will affect the electrical circuit. Since the cable type of 10G SFP+ AOC is fiber, it is immune to interference from electromagnetic during data transmission, while 10G DAC might be susceptible to electromagnetic interference, such as adverse response and degradation. If there are special requirements for the EMI in the network, the 10G AOC will be an ideal solution for secure transmission in large data center networks.
In brief, SFP+ direct attach cable can provide you with a cost-effective and low-power consumption solution for short-distance transmission. Generally speaking, 10G SFP+ DAC cable is perfect for short-reach applications within racks, while 10G SFP+ AOC cable is suitable for inter-racks connections between ToR and EoR switches. You can choose SFP+ cables according to your network needs.