Polarity Validation for MTP/MPO Cables

Posted on Aug 9, 2022

Polarity specifies the direction in which the optical signal travels from one end of the fiber optic cable to the other. For MTP/MPO patch cords, polarity is especially important. When deploying MTP/MPO cables, polarity testing and validation are required to ensure proper data transmission. This article will take you through polarity validation's basis and importance.

What Is Polarity Validation?

Polarity validation refers to testing the polarity of patch cords to verify the correct fiber optic polarity and ensure that the optical signal can transmit data correctly.

In fiber optics, the polarity is directional, and the optical signal is transmitted from one end to the other through the fiber optic cable. The transmit signal (Tx) of the fiber optic link at one end of the cable must correspond to the receiver (Rx) at the other end. Polarity testing effectively ensures the correct polarity, i.e. signals are transmitted from the correct transmitter (TX) to the correct receiver (RX), thus guaranteeing correct data transmission and reception.

Three Polarity Methods for MTP/MPO Systems

TIA specifies three methods of polarity management for MTP/MPO cables, and each uses different types of MTP/MPO cables, so errors often occur during deployment. To avoid these errors, polarity testing or verification is required. The following are the three polarity methods specified by the industry standards for MTP/MPO patch cords.

Type A: On one end is a key-up connector and on the other end is a key-down connector. With type A, the fiber located at Position 1 on one end will reach Position 1 on the other end.

Polarity Type A

Type B: Key-up connectors are used on both ends. The fiber at Position 1 on one connector end arrives at Position 12 on the opposite end, as shown below.

Polarity Type B

Type C: Like Type A, Type C uses different connectors on two ends. Each adjacent pair of fibers is flipped. Therefore, the fiber in Position 1 reaches Position 2 at the opposite end, and the fiber in Position 2 reaches Position 1.

Polarity Type C

Why Is Polarity Validation Important?

Polarity testing and validation significantly affect the effectiveness of connections and subsequent cabling management.

When deploying MTP/MPO fiber cables, proper alignment and mating of MTP/MPO connectors are critical. Poor coupling can hinder signal transmission because the signal may travel in the wrong direction. Polarity testing guarantees correct data transmission.

Unnoticed polarity problems can also increase capital expenditures and technicians' workload. If the polarity problem is not corrected by polarity testing prior to turn-up, technicians will need to work out which cable connections have polarity problems and replace expensive MTP/MPO jumpers, which is frustrating and laborious. As a result, it is best to perform polarity testing in advance to ensure proper connections.

Fiber Polarity Testing for MTP/MPO Fiber Cables

The polarity of MTP / MPO fiber optics needs to be verified with a professional polarity tester. The following video describes the process of MTP/MPO cable polarity testing in detail.

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