Getting an idea of polarity and connectivity is a must to ensure that your MPO/MTP cable assemblies work properly. There are three different connections for such MPO MTP cable assemblies that are called Type A, Type B, and Type C. So, before knowing each method in details, it is important to become familiar with the structure of MTP/MPO connector.

Each MPO/MTP connector has a key on one side of the connector body. When the key sits on top of the connector body, this is referred to as the key up position. Similarly when the key sits on the bottom of the connector body, this is referred to as the key down position. Furthermore, each connector has fiber holes that are numbered in sequence from left to right named as P1(position 1), P2, P3, etc. Additionally, There is a white dot in the connector body that designate P1 of the connector when it is plugged in.  Type A connection is the most straightforward one. It employs a key up MPO/MTP connector on one side and a key down on the other. This allows signals from fiber hole P1 on the key up connector arrive at fiber hole P1 on the key down connector.The attached drawing illustrates the detail of type A,B and C.