Understanding polarity and connectivity is very crucial to ensure that your MTP/MPO fiber systems work properly. There are three different connections in MTP/MPO fiber systems that are called Method A, Method B, and Method C. However, before looking at each method in details, it is important to become familiar with the structure of MTP/MPO connector.
Each of MTP/MPO 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.
This picture describes the basic structure of MTP/MPO connectors.
Method B connection employs a key up MTP/MPO connector on one side and also a key up on the other. This causes signals from hole P1 on the first key up connector arrive at fiber hole P12 on the other key up connector. This drawing describes the Method B connection of MTP/MPO trunk cables.
Fiber Connection
| Key Up |
to |
Key Up |
| Position 1 |
to |
Position 12 |
| Position 2 |
to |
Position 11 |
| Position 3 |
to |
Position 10 |
| Position 4 |
to |
Position 9 |
| Position 5 |
to |
Position 8 |
| Position 6 |
to |
Position 7 |
| Position 7 |
to |
Position 6 |
| Position 8 |
to |
Position 5 |
| Position 9 |
to |
Position 4 |
| Position 10 |
to |
Position 3 |
| Position 11 |
to |
Position 2 |
| Position 12 |
to |
Position 1 |
![Click to enlarge](https://s.turbifycdn.com/aah/fiberopticcables/type-b-trunk-cables-12.gif" rel="lightbox[product])
