Bandwidth is the range of frequencies available for signal transmission. It is measured in hertz. A wider bandwidth means more data can flow. A narrow bandwidth is like a narrow pipe. A wide bandwidth is like a highway with many lanes. The term is also used to describe data rate, though the two are not the same.

In radio, bandwidth is the difference between the highest and lowest frequencies in a channel. A channel from 100 MHz to 110 MHz has 10 MHz of bandwidth. In fiber, bandwidth refers to the range of wavelengths or the data rate the fiber can carry. In networking, bandwidth often means the maximum throughput of a link.

Factors affecting bandwidth

• Spectrum allocation: how much frequency is available
• Modulation: how many bits per symbol
• Signal-to-noise ratio: how clean the signal is
• Medium: fiber has more than copper

Bandwidth is finite. Spectrum is crowded. Fiber has enormous capacity but takes time and money to install. Engineers use compression, modulation, and multiplexing to squeeze more data into the same bandwidth. The demand for bandwidth keeps growing. The supply does not grow as fast.