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.

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.

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.

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.