In modern society, mobile phones have become an indispensable communication tool in our daily lives. When we dial a phone number and talk to relatives and friends far away, there is actually a series of complex and sophisticated working principles hidden behind it. Do you know how signals are transmitted when you are talking to relatives and friends?

The first step in a mobile phone call is the transmission of the signal. When the call is connected, the mobile phone will continue to send signals to the nearby base station, telling the base station to transmit the signal. The base station will transmit the signal to the nearest data center, and then pass the signal through the aggregation layer, backbone network, and core network. After being transmitted, it passes through the core network, backbone network, aggregation layer, and base station, and then the signal is delivered to the target mobile phone. As shown in the figure below, in the process of signal transmission, DWDM optical transmission equipment needs to be used.