As the demand for fast-speed data transmission ever-increases, it is inevitable to migrate from 10G to 40G in data center. However, with the existence of 10G infrastructure, it will cost an amount of money to replace them with 40G devices or equipment. So there come fan-out cabling solutions. Commonly, there are two methods used to migrate from 10G to 40G for short distance transmission: QSFP+ to 4xSFP+ AOC and QSFP+ MTP breakout cable. This post aims to introduce these two types of fan-out cables and tell some differences between them.
40G QSFP+ to 4xSFP+ AOC is a cable assembly, which is composed of a QSFP+ connector on one end and four SFP+ connectors on the other end. This type of fan-out cable can transmit four separate streams of 10Gbps data over ribbon cables in a point-to-multipoint configuration for the link length of 100 meters over OM3 fiber. It offers IT professionals a cost-effective interconnect solution for merging 40G QSFP+ and 10G SFP+ enabled host adapters, switches and servers. Users can directly install this breakout cable between an available QSFP+ port on their 40Gbps rated switch and feed up to four upstream 10G SFP+ enabled switches as shown below.
QSFP+ MTP breakout cable is composed of one MTP or MPO connector on one end for interfacing with QSFP+ port on the 40G switch, while the other end is terminated with four duplex LC connectors for providing connectivity to the SFP+ port on the 10G switch. When we need to achieve the connection between 10G and 40G devices for short distance transmission, besides MTP LC breakout cable, it also requires 40GBase-SR4 or 40GBase-CSR4 and 10GBase-SR4 as shown below.
40GBase-SR4 or QSFP-40G-SR4 can be used in a 4x10G mode for interoperability with 10GBase-SR interfaces up to 100 and 150 meters on multimode (OM3 or OM4) MTP to LC breakout cable respectively, while 40GBase-CSR4 or QSFP-40G-CSR4 can be also used in a 4x10G mode for interoperability with 10GBase-SR interfaces, but it extends the distance up to 300 and 400 meters on multimode (OM3 or OM4) MTP to LC breakout cable respectively.
Performance: As we have mentioned above, both of these fan-out cables can support short link length. Generally, when the transmission distance is less than 100 meters, QSFP+ to 4xSFP+ AOC and QSFP+ MTP Breakout Cable both can be applied, but when it comes to distance over 100 meters, MTP breakout cable has more reliable and better performance than QSFP+ to 4xSFP+ AOC.
Cost: When comparing these two cable types from the aspect of cost, we should take two factors into consideration, one is material cost, and the other is maintenance cost. Actually, in 10G to 40G connection, the total material price of QSFP+ to 4xSFP+ AOC is higher than QSFP+ MTP breakout cable with a 40GBase-SR4 or 40GBase-CSR4 module. For example, 1m QSFP+ to 4xSFP+ AOC is about $200, while 1M MTP to LC breakout cable is $29 with a $55 40GBase-SR4 QSFP+ module and four $16 10GBase-SR SFP+ from FS.COM as show below. However, in modern data center, the value of maintenance cost is much more important than the value of material cost. With QSFP+ to 4xSFP+ AOC, IT managers no longer have to clean the connector as well as terminate plug and test regularly, which can greatly save time and cost.
Installation: As we know, QSFP+ to 4xSFP+ AOC is a cable assembly which has been pre-terminated with one QSFP+ connector on one side and four SFP+ connectors on the other side, so when using it, we just need to plug the connectors directly into the switches, and it works. But for MTP breakout cable, the installation process is a little more complicated. First we have to plug the MTP breakout cable into the QSFP+ and SFP+ interface, and then plug the whole assembly into the switch port.
Both QSFP+ to 4xSFP+ AOC and QSFP+ MTP breakout cable are two good fan-out solutions for the migration from 10G to 40G. But to choose the right one, you have to take some factors into consideration. If the link length you need is long and requires good performance, you should turn to MTP breakout cable and QSFP+ module. But if you are a fresh man in optical deployment, you’d better choose QSFP+ to 4xSFP+ AOC for easier installation and more free from maintenance.
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