Fibre optic 101: The new Base8 vs the old Base12 cable connector history and reasoning
 21 March, 2017 14:07
Corning is known for the tough Gorilla Glass used in phone by many people. But the company is synonymous with fibre optic cables. (Picture: Groman123, Flickr).
What is a Base8 optic fibre connector?
When describing fibre optic links, people will use a variety of terms to describe the link based on the connector type and number of fibres they are using within the link. Base2 is the easiest to understand and visualise. With Base2 connectivity, our links are based on increments of two fibres, such as what is commonly seen with LC duplex or SC duplex connections.
By comparison, Base12 connectivity makes use of links based on increments of 12, with 12fibre connectors such as the MTP. And recently, Base8 connectivity solutions have started appearing. Base8 systems still use the MTPstyle connector, but the links are built in increments of eight fibres, including eightfibre MTP connectors. For example, in a Base8 system, we don’t have 12fibre trunk cables, we have eightfibre trunk cables, and 16fibre trunk cables, and 24fibre trunk cables, and 32fibre trunk cables; all Base8 trunk cables are increments of the number eight. The distinction between Base12 and Base8 is shown in the following figure.
Flashback: The Origin of Base12
Base12 connectivity was first introduced in the mid1990’s, driven by a collaboration between IBM and Corning to develop a modular, high density, structured cabling system which could be deployed in data centres quickly, while also maximizing port densities within the rack space. As data centres grew from just a few fibre connections to data centres where there were thousands or tens of thousands of fibre ports, it was obvious that stringing twofibre patch cords across all corners of the data centre was going to result in an unmanageable, unreliable mess. Given that the TIA/EIA568A fibre colour coding standards are based on groups of 12 fibres, it made sense for high density connectivity to be based on an increment of the number 12, and so the 12fibre MTP connector, and Base12 connectivity, was born.
Trunk cables based on increments of 12fibres, all the way up to 144fibres, were soon available and being deployed globally. Base12 trunk cables are generally used in the network backbone, from the main cross connect out to zone distribution areas, where fibre counts are high, and where high density is essential. To connect to ports on the servers, switches and storage units, most fibre ports are twofibre based, so Base12 to Base2 breakout modules and harnesses are used to provide a twofibre interface for the twofibre port. Since the number 12 is wholly divisible by the number two, we can easily provide the twofibre interface into the network equipment with full fibre utilisation of the Base12 backbone trunk cables.
The Emergence of Base8
Base12 connectivity has served the data centre industry well for almost twenty years. As deployments of the 12fibre MTP connector have grown exponentially over the years, the MTP is now the de facto standard in the backbone for many data centres. However, timestheyareachangin’, and recently the need for Base8 connectivity has become evident. This is due to the types of transceivers that switch, server and storage makers use in their equipment, and the transceiver roadmap which is guiding the industry from 10G Ethernet to 40G and 100G, and even up to 400G.
Technology changes quickly in the transceiver world, but anyone who has installed 40G circuits will know that one of the most common transceiver types is the QSFP transceiver, which utilizes eight fibres. We can use Base12 connectivity to connect to QSFP ports, and indeed many people who are operating 40G circuits today have Base12 connectivity in their backbone, but even the most basic student of math can understand that plugging a 12fibre connector into a transceiver which only requires eight fibres means that four fibres are being unused. There are solutions on the market which enable full 100 per cent utilisation of the backbone fibre in this scenario, via Base12 to Base8 conversion modules or harnesses, but this adds additional MTP connectors, and additional insertion loss, into the link. This is generally not optimal, both for cost and link performance reasons, and so the industry has identified that a better way forward is needed.
That better way is Base8 connectivity. When talking with major transceiver, switch, server and storage makers, it is quite clear that the present, near future, and long term future is full of transceiver types which are based on either Base2 or Base8 connectivity. In other words, for Ethernet transmission ranging from 40G to 400G, all roads lead to twofibre and eightfibre connectivity solutions.
Solution  Reach  40G  100G  400G 
Duplex OM3/4  100150 m  BiDi WDM (UNIV)  BiDi WDM  To Be Determined 
Parallel OM3/4  100150 m  SR4/eSR4 4x10G  Gen1: SR10 10x10G Gen2: SR4 4x25G  Gen1: SR16 16x25G Gen2: SR8 8x50G Gen3: SR4 4x100G 
Duplex Singlemode  210 km  LR4 (10 km) LRL4 (2 km)  LR4 (10 km) CWDM4 (2 km)  WDM(10 km) WDM (2 km) 
Parallel Singlemode  3001,000 m  PLR4  PSM4  PSM4 4x100G (100G via WDM, symbol rate, encoding) 
As the table shows, on the road to 400G, there will be some shortlived solutions, such as the first and second generations of OM3/OM4 parallel transmission, which are being proposed as Base32 and Base16 solutions. However, from Corning’s discussions with prominent transceiver, switch, server and storage vendors, it is not expected that these solutions will be widely deployed, due to manufacturing cost and connector complexity reasons (for example, do you really want to introduce a 32fibre connector into your network?). It is expected that for 400G utilizing parallel transmission over OM3/OM4 fibre, the third generation solution, a Base8 solution, will be what gains widespread market acceptance.
Since the number eight is wholly divisible by the number two, Base8 backbone connectivity can be easily used for twofibre transceiver systems, just as Base12 connectivity can be. However, Base8 connectivity provides the most flexibility for what are expected to be the most common 40G, 100G and 400G transceiver types, as Base12 connectivity is not optimal for eightfibre transceiver systems. Simply stated, Base8 connectivity provides the most future proof solution out to 400G transmission requirements.
Can Base8 and Base12 be Used Together?
Well, yes and no. It depends on how you define the words “used together.” If you mean directly mixing the components, and plugging a Base8 trunk into a 12fibre module, then the answer is a definitive “No.” The components are not designed to be plugged directly into each other, and as such, Base12 and Base8 MTP systems are designed with visual differences, so that mixing Base8 and Base12 components in a single link can be avoided. A key reason for the visual differences is that Base12 trunk cables generally have unpinned MTP connectors on both ends, and require the use of pinned breakout modules. However, the emerging Base8 trunk cables are manufactured with pinned connectors on both ends. So plugging a Base8 trunk cable into a Base12 breakout module definitely won’t work, as that would mean trying to mate two pinned connectors together. The reason for this change in the trunk cable pinning scheme is that this provides the advantage of ensuring that wherever it is used in the network, a Base8 MTP patch cord can always have unpinned connectors on both ends. This simplifies the network deployment and eliminates the need to stock multiple pinning configurations of MTP patch cords.
However, if by “used together” you mean having both Base8 and Base12 connectivity in the same data centre, then the answer is “Yes,” although this “Yes” comes with a caveat. The caveat is that the Base8 and Base12 links have to be maintained independently, because as previously stated the Base8 and Base12 components themselves are not interchangeable, and Base8 and Base12 components cannot be plugged into each other within the same link. So some care is required when managing the data centre physical layer infrastructure, to ensure that Base8 and Base12 components are not mixed within the same link.
Base8 versus Base12: How to Choose?
Since the number 12 is obviously larger than the number eight, Base12 connectivity does provide the benefit of higher connector fibre density compared to Base8, and thus a larger number of fibres can be installed more quickly when using Base12 connectivity. However, as a greater number of 40G and 100G circuits are deployed which utilize eightfibre transceivers, the benefits of matching the fibre count in the MTP backbone connectivity with the fibre count of the transceiver tends to outweigh the density benefit of Base12 connectivity. In addition, when using MTP to LC duplex breakout harnesses to connect to switch line cards, the Base8 harnesses easily route to all common port count line cards, as all common line cards contain a number of ports wholly divisible by the number four (since a Base8 harness provides four LC duplex connections). In the case of Base12 harnesses which provide six LC duplex connections, these harnesses do not as easily route to lines cards with 16 or 32 ports, since the numbers 16 and 32 are not wholly divisible by the number six. The following table describes the relative benefits when comparing Base8 versus Base12 connectivity for a data centre deployment.
Benefits of Base8  Benefits of Base12 


Although the fibre per connector density cannot be overlooked, for most people the decision will come down to how quickly they are migrating to 40G and 100G network speeds. Anyone with a nearterm migration plan to adopt 40G or 100G in their data centre will find great benefit in adopting Base8 connectivity today.
The Bottom Line
Both Base8 and Base12 connectivity will continue to be used in the data centre for many years to come. Both have their benefits, and both will have their place in the data centre, with the usage of 40 and 100G transmission being a key deciding factor. If you are using Base12 connectivity in your data centre today and you are happy with it, then it is perfectly fine to continue using Base12. Base8 connectivity is just an additional option in the network designer’s tool kit to ensure that data centres have the most cost effective, future proof network available, with a migration path that easily scales out to 400G transmission.
Clive Hogg is Technical Sales Manager, Enterprise Networks at Corning Optical Communications