This is a simulation that you can download and run on your Windows computer. Below is a screen shot demonstrating pulse modulation. If you decide to download and install the simulation program, you will be able to run this simulation on your computer and change the settings shown below.
The blue wave that you will see is called the "carrier wave". This is the wave that you can send over the radio or through a fiber optics line. The three pulses shown below represent digital bits that we are attempting to transmit via the carrier wave.