It is important to ensure that the optical transmitter at one end is connected to the optical receiver at the other in any installation. This matching of the transmit signal to the receiving equipment at both ends of the fiber optic link is referred to as polarity. For traditional cabling systems using single fiber connectors, such as SC or LC, Keeping the polarity simple is to ensure that one connector has one side, one pair of matching B side, and the other connector on any incoming line or permanent link. But for the high-density MTP/MPO array connectivity systems, it has their own requirements for maintaining proper polarity. Now Sinda will illustrate the methods for maintaining polarity in pre-terminated MTP systems.
MTP/MPO Array Connector Structure
Array connectors terminate multiple fibers in a single high-density interface. There are 4, 6, 8, and 12-fiber array connectors. And the most common are 12-fiber array connectors. As shown in the following picture, array connectors are pin and socket connectors, there are a male side and a female side. As well as, each MTP connector has a key on one side of the connector body. When the key sits on top, this is referred to as the key up position. In this orientation, each of fiber holes in the connector is numbered in sequence from left to right. We will refer to these connector holes as positions, or P1, P2, etc. In addition, each connector adds a white dot to the connector body so that the connector’s location 1 is specified when the connector is inserted.
Three Polarity Methods for MTP/MPO Systems
Three different ways for maintaining polarity in pre-terminated MTP systems are defined in TIA/EIA-568-B.1-7. These three ways define installation and polarity management practices and provide guidance in the deployment of these types of fiber array links. Once you choose one way, These practices must be in place to ensure that the correct signals are delivered throughout the installation.
Method A employs “key up to key down” adapters to connect the array connectors. As shown below, this method maintains registration of Fiber 1 throughout the optical circuit. The optical fiber 1 in the proximal box matches the optical fiber 1 in the relay component that is matched with the fiber 1 in the relay box. Optical fiber circuits are accomplished by using a flipped jumper at the beginning or end of the permanent link to ensure that the transceiver is in the right direction.
Method A provides the simplest deployment and works for single-mode and multimode channels, as well as can easily support network extensions.
Method B uses “key up to key up” adapter. An optical fiber circuit is accomplished by using a direct patch at the beginning and end of the link, and all array connectors match the key up key”. MThis type of array mating results in an inversion, meaning that Fiber 1 is mated with Fiber 12, Fiber 2 is mated with Fiber 11, etc., to ensure that the appropriate configuration of transceiver operation, a box must be inserted into the internal fiber optical fiber link with 1 at the end of 12.
Method C uses “key up to key down” adapters. The fiber circuit is completed by utilizing straight patch cords at the beginning and end of the link, and the same cassettes as in Method A. The difference between this method and Method A is that the flip does not happen in the end patch cords but in the array cable itself.
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