The ANSI/TIA 568-3.D, (Optical Fiber Cabling and Components Standard, October 2016) defines three pinning or types for multi-fiber array systems: Method A, B and C. While one method is not preferred over another, the standard recommends that you choose a method in advance and use it throughout your installation. To maintain the proper polarity, there are three connectivity methods—A, B, C—that mirror the cable types. Each polarity method handles the transition from transmit to receive in a different manner.
- Method A, straight-through, is the most commonly used approach. It is pin 1 to pin 1 and uses Method A (key-up to key-down) MPO connectors.
- Method B is a crossover method (pin 1 to pin 12) and uses method B (key-up to key-up) MPO connectors.
- Method C uses flipped pairs (pin 1 to pin 2) and method A (key-up to key-down) MPO connectors. It does not offer a migration pathway to 40-/100-GbE.