It is a long-established protocol within the fibre communications industry to have a Transmitter TX and a receiver RX to transmit and receive data. Its why we have a duplex patch cord. The majority of legacy installations will have duplex fibre connections for TX & RX. Having dedicated lines for TX & RX is costly. Need higher fibre count cables bigger diameters, occupies more space on installations and comms rooms real-estate, limits capacity. The possible solution sends both TX & RX down the same Fibre this would double capacity on legacy systems and possibly be a more cost-effective solution on new installations. This is better known as Single Fibre Solution, which is Bi-Directional BiDi.
