Understanding MTP Components & Its Polarity in 40/100GbE Transmission
To accommodate the increasing demands for high-speed data transmission and great data capacity, data centers are moving to 40G and 100G transmission networks now. It’s known that 40/100G Ethernet implementations over multi-mode fibers (MMFs) use multiple parallel 10G connections that are aggregated. 40G uses four 10G fibers to send and four 10G fibers to receive, while 100G uses ten 10G fibers in each direction. To ensure that fiber systems work smoothly, each fiber must have a transmitter at one end, and a receiver at the other.
For multi-fiber arrays using MPO/MTP connectors, the TIA 568 standard provides three methods for configuring systems to ensure that proper connections are made, Methods A, B & C. Each of these methods handle the transition from a transmit position to a receive position in a slightly different manner. This article mainly discusses MPO/MTP polarity and its components in 40/100GbE transmission, and the rest passages will only mention MTP instead of MPO/MTP for simpleness.
MTP Components
MTP connector: Each MTP connector has a key on one side of the connector body. When the key sits on the bottom, this is called key down. And when the key sits on top, this is referred to as the key up position. In this orientation, each of the fiber holes in the connector is numbered in sequence from left to right. Here refers to these connector holes as positions, or P1, P2, etc.. Each connector is additionally marked with a white dot on the connector body to designate the position 1 side of the connector when it is plugged in.
MTP Adapter: MTP adapter is used to connect two MTP connectors. This adapter on a cassette is simply a holder with keying designed to hold the two facing ends of the MTPs in correct alignment. The following image shows how the two MTPs are held with the adapter.
MTP Cable: MTP trunk cables serve as a permanent link that connects MTP modules to each other. Available with 12, 24, 48 and 72 fibers, these cables are used to facilitate rapid deployment of high density backbone cabling in data centers and other high fiber environments reducing network installation or reconfiguration. A 72-fiber MTP trunk cable can be terminated with 6 MTP connectors which are manufactured specifically for multi-fiber loose tube or ribbon cable.
MTP harness cables are often terminated with a male/female connector on the MTP side and several duplex LC/SC connectors on the other side, providing a transition from MMFs to individual fibers or duplex connectors. This kind of cable assembly provides a reliable, cost-effective cabling system for migrating from legacy 10G to higher speed 40G/100GbE. For instance, 12-fiber MTP to 4 duplex LC can be used to connect four 10 gig SFP (SFP-10G-SR) with one 40G QSFP+ module (40G-QSFP-SR4).
MTP Cassette Modules: These modules permit rapid deployment of high density data center infrastructure as well as improved troubleshooting and reconfiguration during moves, adds and changes. They enable users to take the fibers brought by a trunk cable and distribute them to a duplex cable. As already assembled units, the MTP cassette modules are fitted with 12 or 24 fibers and have LC, or SC adapters on the front side and MTP at the rear, this is to say, inside a standard LGX cassette module, there is a hydra cable.
MTP Polarity Methods
Method A, Method B and Method C are the defined methods by TIA 568 standard for proper polarity. To understand these methods, MTP truck cables are used as the object.
Method A: For this method, the transmit‐receive flip must happen in the patch cords, and the trunk cable is a straight through transmission, with the key up on one end, and the key down on the opposite end(image below).
Method B: This method uses key up connector on both ends of the cable. This type of array mating results in an inversion, which means the fiber positions are reversed at each end. The fiber at P1 at one end is mated with fiber at P12 at the opposing end.
Method C: This method one key up connector and one key down connector. Each adjacent pair of fibers at one end are flipped at the other end. For example, the fiber at position 1 on one end is shifted to position 2 at the other end of the cable. The fiber at position 2 at one end is shifted to position 1 at the opposite end etc.
40/100G Transmission Connectivity
For 40G transmission using 12-fiber MTP connectors, it transmits 40G using four parallel 10G lanes in each direction. More specifically, there are eight lanes within twelve total positions being employed for transmitting and receiving signals. The four leftmost positions are used to transmit, and the four rightmost positions are used to receive, leaving the four in the center are unused.
For 100G transmission, there are multiple configurations (shown above). However, increasingly it appears that the single port 24-fiber connector is the preferred approach once connector loss is improved.
Conclusion
When it comes to the high networking capacity, it’s no doubt that MTP cable comes as the suitable solution. Select the right polarity method, and then high density and reliability can be achieved. As a professional fiber patch cord manufacturer, Fiberstore supplies various MTP components, including MTP cables, adpaters, connectors, cassettes. You can try here.
