Since fiber optic data transmissions in networking use square waves, it is a digital signal. However, you can also transmit a analog signal over fiber optic, such as a video. It is not the medium that determines the type of signal, but the devices on each end. Fiber is preferred. There are many differences between analog and digital, but one of the primary distinctions that will easily answer your question is that analog signals make use of sine waves while digital signals make use of square waves. digital signal (1s and 0s). Analog signals are continuously variable signals where the information in the signal is contained in the amplitude of the signal over time.