Input port: An input port is a port that inputs signals or energy into the coupler. It is usually connected to a source device or signal source to transmit signals or energy to the coupler.
Output port: An output port is a port that outputs signals or energy from the coupler. It is usually connected to a load device or receiver to receive the signal or energy from the coupler.
Coupling port: A coupling port is a port for connecting two or more couplers. It allows signals to be transmitted between different couplers to realize signal distribution, combination or forwarding.
The purpose of the three ports of the coupler can be determined according to the specific application scenarios and design requirements. For example, in a wireless communication system, an input port is usually connected to an antenna, an output port is connected to a receiver or a transmitter, and a coupling port is used to connect different couplers to realize signal distribution or combination. In the optical fiber communication system, the input port is connected to the optical fiber transmitter, the output port is connected to the optical fiber receiver, and the coupling port is used to connect different optical fiber couplers to realize the transmission and distribution of optical signals.