The A/B end is the two ends of the optical fiber transmission. No matter what the two ends are, they must be A and B to be paired for use (the product model is marked as the A end or the B end). To comply with these standards, three types of MTP optical fibers with different structures are currently in use, namely Type A, Type B, and Type C, for. Fiber optics relies on a bidirectional transmission where the transmitter port on one end connects to the receiver port on the other end. A link's transmit signal (Tx) must match its corresponding receiver (Rx) at the other end. There are also fiber-to-fiber versions that translate between different fiber types, wavelengths, or distances.