directional coupling

Directional Coupling is a term from Fibernet II. The high-speed fiber optic networks that have been in use for some time, with speeds of over 100 Mbit/s and an extension of approx. 200 km, follow the IEEE 802 standard, i.e. also the CSMA/ CD method.

The problem on fiber optic networks is collision detection. In CSMA/CD networks based on coaxial cable, a transmitting station's own signal is compared with the signal on the cable; if the two do not match, a collision has occurred. This procedure is not applicable to optical fibers.

One of the ways to detect collisions also on optical fibers is directional coupling. In this case, the signal of the transmitting station is optically masked so that the receiving system of the transmitting station does not find any input signal. If a signal is nevertheless present, it can only be a collision and the steps known from CSMA/CD and required are initiated.