Polarization-division multiplexing

Polarization-division multiplexing (PDM) is a way of sending multiple things on the same connection at the same time. Think of it like a highway. Normally, only one car can go on the highway at a time. But with PDM, four cars could go at the same time. But instead of these cars being regular cars, they are signals that carry different kinds of information. These signals travel on two different lanes of the highway using something called "polarization". Each lane is called a "polarization". The cars on each polarization contain different kinds of information. So, instead of four whole cars on the highway, you can send four separate signals in the same place. It's like having four lanes of traffic in one place!