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
- Method B is a crossover method (pin 1 to pin 12) and uses method B (key-up to key-up) MPO connectors.
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.