Base2 connectivity is a common type of fiber optic link in today’s 10G network, such as LC duplex or SC duplex connections. With Base2 connectivity, the fiber links are based on increments of two fibers. However, this kind of connectivity can not meet the demands of 40G links for the reason that numerous 2fiber patch cords in the data center will result in an unmanageable, unreliable mess. Therefore, Base12 and Base8 connectivity are introduced successively to develop a modular, high density, structured cabling system for 40G network. Then, which is more suitable for the 40G links, Base8 or Base12 connectivity?
This part will give a brief introduction to Base12 connectivity and Base8 connectivity respectively.
Inspired by the fact that the TIA/EIA568A fiber color coding standards are based on groups of 12 fibers, it makes sense that high density connectivity can be based on an increment of the number 12. Thus the 12fiber MTP connect and Base12 connectivity were born in the mid1990’s. In a Base12 system, Base12 connectivity makes use of links based on increments of 12 fibers with 12fiber MTP connectors (as shown in the following figure).
Due to the quicklychanging technology associated with transceivers, switches and servers, data centers that want to keep up may need to use Base8 connectivity. This is because the present, near future, and long term future is full of transceiver types which are based on either Base2 or Base8 connectivity. The Base8 system still uses the MTP connector, but the links are built in increments of 8 fibers (as shown in the following figure). Thus there are 8fiber trunk cables, 16fiber trunk cables, 24fiber trunk cables and so on.
It is known to us that transmission at 40G is mainly based on using eight fibers in the link–four for transmitting and four for receiving at 10G (as shown in the following figure). In addition, QSFP transceivers and MTP connectors are commonly used in the 40G network. Thus we can use Base12 connectivity and Base8 connectivity to connect to the QSFP ports.
If Base12 connectivity is used in the 40G network, it is easy to figure out that plugging a 12fiber connector into a QSFP transceiver only requiring eight fibers means four fibers are being unused. Thus, there appears Base12 to Base8 conversion modules or harnesses to enable the full utilization of the backbone fiber. The followings are three common solutions of Base12 connectivity for 40G network:
Seen from the above picture, there are four unused fibers in solution 1, which leads to a significant and costly loss in fiber network utilization; solution 2 and solution 3 add additional MTP connectors and additional insertion loss into the whole link. In this case, Base12 connectivity is not the optimal solution in 40G network both for cost and link performance reasons.
Unlike Base12 connectivity, Base8 connectivity enables 100% fiber utilization for QSFP transceivers without any additional cost and insertion loss of Base12 to Base8 conversion devices. And its cabling is much more simple and flexible (as shown in the following figure). The imperfection of Base8 connectivity is that it does not provide as high connector fiber density as that of Base12 connectivity.
Though Base8 connectivity is superior to Base12 connectivity in some aspects, both Base8 and Base12 connectivity will be used in the data center for many years to come. In fact, Base8 connectivity isn’t an universal solution and Base12 connectivity in some cases may still be more costeffective. The following table clearly shows the benefits of Base8 connectivity and Base12 connectivity:
Benefits of Base8 Connectivity  Benefits of Base12 Connectivity 

