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March 4, 2020

As we all know, traditional Base-2 connection (LC cabling) can not meet the high speed and high density demand of the data center deployed with 40G or 100G. Under such circumstances, two new connection methods — Base-12 and the later Base-8 MTP/MPO connections have been adopted in many cases. Then, What are Base-12 and Base-8 MTP cabling? Which should we choose in our MTP cabling system? Get details from the following text.

Note: MTP® is a registered trademark of US Conec Ltd. . This is the term US Conec uses to describe their connectors. American Conec MTP products are fully compliant with MPO standards. Therefore, the MTP connector is a type of MPO connector.

A Base-8 MTP/MPO cabling is based on Type B male/pinned MTP trunk in the backbone. It makes use of fiber optical links based on increments of 8 fibers and 8-fiber MTP fiber optic connectors. For example, trunk cables of 8-fiber, 16-fiber and 24-fiber all belong to Base-8 MTP cabling system. In Base-8 MTP cabling, 12-fiber trunk cables don't exist. The following picture shows what the Base-8 cabling system is like:

Base-8 connectivity can be easily used for Base-2 cabling systems since the number eight is wholly divisible by the number two. For example, an 8-fiber MTP cable could be easily converted to 4 duplex LC cables. Of course, you can use other solutions like MTP-LC modules to realize the smooth conversion from Base-8 to Base-2 connectivity.

A Base-12 MTP/MPO cabling is based on Type A female/unpinned MTP trunk in the backbone. It makes use of fiber optical links based on increments of 12 fibers and 12-fiber MTP fiber optic connectors. Base-12 appears ahead of Base-8. Therefore, it still remains the mainstream in MTP cabling system. Here is what a Base-12 connectivity like:

Likewise, Base-12 connectivity can be easily used for Base-2 cabling systems since the number twelve is wholly divisible by the number two as well. Here is a picture showing the conversion from Base-12 to Base-2 system using MTP-LC breakout modules.

Base-12 connectivity has served the data center industry for nearly 20 years. The deployment of 12-fiber MTP connectors has grown exponentially throughout the process. However, as the transceivers used by switch, server, and storage manufacturers in their equipment have changed gradually from 10G Ethernet to 40G and 100G, and even up to 400G, the need for Base-8 connectivity is becoming increasingly apparent. The following table illustrates the cabling differences at different rates:

Solution | Reach | 40G | 100G | 400G |
---|---|---|---|---|

Duplex OM3/4 | 100-150 m | BiDi WDM (UNIV) | BiDi WDM | To Be Determined |

Parallel OM3/4 | 100-150 m | SR4/eSR4 4x10G | Gen1: SR10 10x10G; Gen2: SR4 4x25G |
Gen1: SR16 16x25G; Gen2: SR8 8x50G; Gen3: SR4 4x100G |

Duplex Single-mode | 2-10 km | LR4 (10 km); LRL4 (2 km) | LR4 (10 km); CWDM4 (2 km) | WDM(10 km); WDM (2 km) |

Parallel Single-mode | 300-1,000 m | PLR4 | PSM4 | PSM4 4x100G (100G via WDM, symbol rate, encoding) |

From the above, we can consider from the following two main aspects to decide whether to choose Base-12 or Base-8:

In high-density network cabling, Base-12 is more advantageous because it has more cores and higher density. However, it is obvious that Base-8 MTP cabling has better fiber utilization than Base-12 MTP cabling. Although the Base-12 MPO cabling is still the most common choice for most data center operators, there are still no standardized transceivers using all 12 fibers. Many popular transceivers (SR4 transceivers, for example), only use 8-fiber interface. Base-8 MTP links allow customers to directly connect fibers to those transceivers, without any fiber waste. If we use a 12-fibre connector into a transceiver which only requires eight fibers, it means that four fibers are being unused. You may consider using a conversion cable to convert the Base-12 cabling to Base-8 cabling (two Base-12 to three Base-8, for example) to make use of all fibers. However, it will cause additional insertion loss, reducing the cable performance.

In addition, when using MTP to LC duplex breakout harnesses to connect to switch line cards, the Base-8 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 Base-8 harness provides four LC duplex connections). If you use Base-12 MTP to LC duplex breakout harnesses, you will get 6 LC duplex connections. But these harness cables can't fully connect to line cards with 16 or 32 ports since 16 and 32 are not wholly divisible by 6.

Therefore, for the sake of fiber utilization, Base-8 MTP cabling is a better choice. Of course, if you don't mind the fiber wasting, Base-12 MTP cabling could also be selected.

Both Base-12 and Base-8 MTP cabling can be seamlessly converted to Base-2 cabling in relatively smaller networks like 10G connection. Under such circumstances, either of them is feasible. However, for bigger networks like 40G, 100G or even 400G connection, a Base-8 solution will gain more widespread market acceptance since a greater number of 40G and 100G circuits are deployed utilizing eight-fiber transceivers. So do 400G direct connections which use 400G QSFP-DD transceivers and MTP-16 trunk cable. In addition, the 8-fiber cabling could work with the 24-fiber cabling seamlessly since a single 24-fiber MPO could break out to three 8-fiber MPOs. Customers deploying 10G data rates today can still deploy the Base-8 system since upgrades to 40G or 100G will be much simpler and cost effective in the future. While, Base-12 connectivity is not optimal for 8-fiber transceiver systems.

**Q: Can We Use Base-8 and Base-12 Together Directly?**

A: It is never possible to directly mix the components of Base-8 and Base-12 connectivity, or plug a Base-8 trunk into a 12-fiber module. Because a Base-12 trunk cable normally has unpinned MTP connector on both ends, and requires the use of pinned 12-fiber breakout modules, while a Base-8 trunk cable is manufactured with pinned MTP connectors at both ends.

**Q: Is It Possible to Use Base-8 and Base-12 Cabling in the Same Data Center?**

A: It is possible to deploy both Base-8 and Base-12 connectivity within the same data center, just as long as the links are separate.

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