What are MTP / MPO Fiber Cables?

MTP/MPO — High-Density Fiber Optic Cabling 
The quantity of data transmitted worldwide is growing exponentially and the need for ever-greater bandwidths is unrelenting. Though the current data volumes demanded in backbone cabling can still be handled with 10 GbE, the forecast trends will require the introduction of the next technologies, 40 GbE and 100 GbE. As a result, data centers must respond to provide sufficient capacities and plan for upcoming requirements. To meet this demand, 40G QSFP+ transceivers, MTP/MPO cables and other related products are now in the market. MTP/MPO cables in the data centers play an important role in ultra-high density cabling.

Why are MTP/MPO Cables Used? 
The number of network connections in data centers is rising rapidly. Traditional fiber cables can make the data center crammed and difficult to manage. To solve this problem, data centers have to achieve ultra-high density in cabling to accommodate all of the cabling required. The MTP/MPO cables, which bring together 8, 12 or 24 fibers in a single interface have been proven to be a practical solution. Incorporating to meet the 40GBASE-SR4 and 100GBASE-SR10 standard, The MTP/MPO multi-fiber connector of MTP/MPO cables is about the same size as a SC connector but can accommodate 8, 12 or 24 fibers, thus offering savings in circuit card and rack space.

Details of MTP/MPO Cables 
MTP/MPO cables are composed of MTP/MPO connectors and fiber optic cables, other connectors such as LC may also be found in some kinds of MTP/MPO cables. The fiber cables used are generally OM3 and OM4, which are laser optimized multi-mode optical fibers. It is important to have an overall understanding of MTP/MPO connectors (known as multi-fiber push-on and also as multi-path push-on).
MPO connectors are available in a female version (without pins), or a male version (with pins) as shown in the following picture. The pins ensure the exact alignment of the fronts of the connectors, and also they ensure the end faces of the fibers are not offset.

Noses and guide grooves (key) on the top side are the two other clearly visible features, which ensures the adapter hold the connector with the correct ends aligned with each other. Based on the placement of the key, two types of MPO adapters are available. One is “key-up to key-down”. It means the key is up on one side and down on the other. The two connectors are connected turned 180° in relation to each other. The other one is “key-up to key-up”. It means both keys are up. The two connectors are connected while in the same position in relation to each other.   

Connection Rule

  • Always use one male connector and one female connector plus one MPO adapter when creating a MPO connection (see the following picture).

  • Never connect a female to a female or a male to a male. It should be connected with a male and a female as stated above. With a female-to-female connection, the fiber cores of the two connectors will not be at the exact same height because the guide pins are missing. That will lead to losses in performance. A male-to-male connection has even more disastrous results. There the guide pins hit against guide pins so no contact is established. This can also damage the connectors.
  • Never dismantle a MPO connector. The pins are difficult to detach from a MPO connector and the fibers might break in the process. In addition, the warranty becomes null and void if you open the connector housing.

MTP/MPO Cables 
MTP/MPO Cable has the advantages of shorter installation times, tested and guaranteed quality and greater reliability. It has several different kinds of types.

Trunk Cables: trunk cables serve as a permanent link connecting the MTP/MPO modules to each other. They are available with 12, 24, 48 and 72 fibers. Their ends are terminated with 12-fiber or 24-fiber MTP/MPO connectors according to customer's choice. These trunk cables like 12 fibers MPO trunk cable could help to create a simple, cost-effective 40G networking by installing a structured cabling system. MTP/MPO trunk cable requires greater care in planning but has a number of advantages, such as higher quality, minimal skew, shorter installation time, better protection, smaller volume of cable and lower total costs.

Harness Cables: harness cables provide a transition from multifiber cables to individual fibers or duplex connectors. For instance, 8 fibers 12 strands MTP/MPO harness cable has eight LC high fiber density connectors and a MPO connector, which is convenient for wiring and management system in 40G network with stable performance.

Y Cables: Y cables are generally used in the 2-to-1 version. A typical application is to join two 12-fiber trunk cables to a 24-fiber patch cord as part of a migration to 100 GbE. The rather rare version of 1 to 3 allows three eight-fiber MTP/MPO connectors to be joined to a 24-fiber permanent link, e.g. for migration to 40 GbE.

MTP/MPO Solutions for 40 Gigabit Ethernet Cabling 
OM3 and OM4 fiber optic cables put in a parallel optical connection, terminated with MTP/MPO connectors. These are the ingredients for 40 GbE technology in a structured cabling environment. Parallel optical channels with multifiber multimode optical fibers of the categories OM3 and OM4 are used for implementing 40 GbE. The small diameter of the optical fibers poses no problems in laying the lines, but the ports suddenly have to accommodate four or even ten times the number of connectors. This large number of connectors can no longer be covered with conventional individual connectors. So the 802.3ba standard incorporated the MPO connector for 40GBASE-SR4.

By Polarity

MTP®/MPO cable types by polarity refer to the difference between the optical transmitters and receivers at both ends of the fiber link. Due to the special design of MTP®/MPO connectors, polarity issues must be addressed in high-density MTP®/MPO cabling systems.

The TIA 568 standard defines three connection methods to ensure the correct polarity of the optical path, called Type A, Type B, and Type C. The cables of the three MTP®/MPO connector types have different structures.

MTP/MPO connectors and cables are the central components of a 40G parallel optical link. This connection decides whether the insertion loss exceeds the attenuation budget and whether the return loss is high enough. In the end, the desired bandwidth can only be reached if all components in a parallel optical link satisfy the highest requirements.