Some Thoughts Required Before MTP Cabling

To meet system bandwidth needs and provide higher density cable connectivity, building backbones and data center backbones are migrating to 40G and 100G Ethernet network. Making the migration path smooth has become a hotspot. Network designers are turning to MTP components which can provide cost-effective solutions for cabling systems of data centers. We know that MTP components are designed with complex structures, so before you start your 40G Ethernet network deployment, there are a few aspects of MTP cabling that require some thoughts.


First and foremost is the polarity. With the LC connector typically used for 1G and 10G fiber cables, this isn’t a big deal. You can flip the two fiber strands on the LC connector easily to invert the polarity if needed. However, the MTP connector is fixed, you can’t change the ordering of the strands in the connector. Take 12-fiber MTP trunk cable for example, it is made up of 12x individual strands of fiber and one 12-fiber MTP connector on each end. Typically in 40G Ethernet network deployment, the 12-fiber MTP cable transmits optic signals on first 4x strands, and receives optic signals on the last 4x strands. The 4x “transmit” strands in MTP connector on one end need to end up at the “receive” strands in MTP connector on the other end. In other words, 8 of the 12 fibers are used to provide 40G parallel transmission and the polarity of the cable has to be inverted between the two devices. In addition, there are three polarity methods for MTP cabling. Each of them has different features. It is recommended that a method be selected in advance according to the specific requirements of the cabling situation and maintained consistently throughout an installation.

Gender of MTP Connector

Another issue with MTP components to take into consideration is the gender of the connector going into the adapter matter. There are male connector and female connector. And the former one has pins while the latter one has no pins. One cable going into a MTP adapter needs to have a male connector and the other cable must have a female connector. This is not initially obvious to those who have little knowledge about MTP components. If you only have MTP cables with female connectors, they can be snapped into the adapter just fine, but will not work. The figure below shows the difference between the structure of male and female MTP connector.

male and female MTP connector in MTP cabling

Key Position of MTP Adapter

MTP adapter, or MTP coupler, is simple plastic rectangle that holds two MTP connectors together. The other important factor to note about MTP adapter is that they can be either key-up to key-up, or key-up to key-down, and this corresponds to the key position of MTP connector. When the key sits on top, this is referred to as the key up position. On the contrary, when the key sits on bottom, we call it key down position. On a key-up to key-up adapter, the keys are pointed the same direction on both of the connectors. While on a key-up to key-down adapter, the keys are on opposite sides. This can effect the polarity of the fiber link. To have a better understanding of this, here is a figure for you.

key position of MTP adapter in MTP cabling


Being able to provide an easy migration path for higher data rates that will require parallel optics such as 40/100G Ethernet network, MTP cabling is commonly used by network designers to satisfy the increasing demands for higher transmission speed and cabling density. However, before the installation, three major problems—polarity, gender of MTP connector and key position of MTP adapter have to be solved to ensure the smooth data transmission over the optical links.

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MTP Cabling: 12-Fiber or 24-Fiber?

With the rapid development of network technology, migration to ever higher speed data transmission networks becomes the trend. As 10G Ethernet is commonly used in larger enterprises, migration from 10G to 40G to 100G is underway to meet the demands for higher bandwidth. Has your network cabling been optimized for this inevitable growth? It is essential to create a simple, cost-effective migration to support the needs of 40G/100G Ethernet network. MTP cabling is a good solution for both 40G and 100G network migration. This article will focus on the difference between 12-fiber and 24-fiber MTP cabling from three aspects—migration, cost and density.


Trunks, harnesses, patch cords, modules and adapter plates are the necessary components used in the network. The following diagrams show the 12- and 24-fiber system configurations from 1G to 100G networks.

Figure 1. shows 12-Fiber MTP cabling for 40G. In this type of cabling system, one 12-fiber MTP trunk cable, two 12-fiber MTP-LC modules and two LC duplex patch cords are needed.

12-fiber MTP cabling for 10G

Figure 1.—1/10G Channel 12-Fiber Legacy Configuration

Figure 2. shows two options for 12-Fiber MTP cabling for 40G. In this type of cabling system, a second MTP trunk cable and another set of array harnesses will be needed to achieve 100% fiber utilization.

12-fiber MTP cabling for 40G

Figure 2.—40G Channel 12-Fiber Legacy Configurations

Figure 3. shows 12-fiber MTP cabling for 100G. In this type of cabling system, for 100G, some additional components will be required for any 12-fiber legacy configuration, like MTP adapter plate and MTP harness cable.

12-fiber MTP cabling for 100G

Figure 3.—100G Channel 12-Fiber Legacy Configuration

With the use of 24-fiber MTP trunk cable, a single cable can support a 1G-100G channel and will simplify network upgrades immensely. 1G and 10G networks will link the MTP trunk cables to active equipment with MTP-LC modules and LC duplex patch cords. When equipment is upgraded, modules and patch cords are exchanged for the appropriate new MTP components, with no need to install new trunks. In addition, limiting changes reduce the inherent risks to network security and integrity whenever MAC work is completed. The following three figures separately show 24-fiber MTP cabling for 10G, 24-fiber MTP cabling for 40G and 24-fiber MTP cabling for 100G.

24-fiber MTP cabling for 10G

1/10G Channel 24-Fiber Configuration

24-fiber MTP cabling for 40G

40G Channel 24-Fiber Configurations

24-fiber MTP cabling for 100G

100G Channel 24-Fiber Configuration


12-fiber configuration may allow you to continue to use existing MTP trunk cables when upgrading your equipment (if you already have 12-fiber MTP/MPO trunk cables), but it will be likely to require additional MTP trunk cables, more connectivity components, and other network modifications. In the long run, it is much more expensive to retain these MTP trunk cables than to upgrade to 24-fiber up front.


High speed data transmission needs high density cabling in data center. Many data center managers prefer network components which can realize both high density connectivity and smaller occupation space in the enclosure which can leave more rack space for active equipment and reduce the total amount of floor space required. 24-fiber cabling has the obvious advantage. If the active equipment is configured for 24-fiber channel/lane assignments, enclosures can have twice as many connections with the same number of ports compared to 12-fiber (or the same number of connections using only half the ports).

The flip side of density is congestion. The more connectivity you are able to run in the same footprint, the more crowded it can become at the rack or cabinet. Here again, 24-fiber MTP trunk cable offers a huge benefit. Anywhere there is fiber, from within the enclosures to cable runs that connect different areas of the network, you will have just half the number of cables versus 12-fiber. Runs carry a lighter load, fibers are easier to manage, and improved airflow saves cooling costs.


Fewer connectivity components to be replaced or added simplifies migration and saves costs for both components and installation. Higher-density connectivity leaves more rack space for active equipment. And fewer MTP trunk cables reduce cable congestion throughout the data center. In a word, the 24-fiber MTP cabling will future-proof your network, lower your cost and maximize your return on investment.