Multiplexing combines multiple signals into one transmission channel. It lets many users or data streams share the same medium. Without it, every call would need its own wire. With it, thousands of calls travel over one fiber. Multiplexing is how telecom networks achieve scale.

There are several types. Frequency division multiplexing divides the channel into frequency bands. Time division multiplexing divides it into time slots. Wavelength division multiplexing divides fiber into light wavelengths. Code division multiplexing assigns unique codes. Each type suits different media and requirements.

Multiplexing types

• FDM: frequency bands
• TDM: time slots
• WDM: light wavelengths
• CDM: unique codes
• OFDM: orthogonal subcarriers

Multiplexing is essential. It reduces cost, increases capacity, and improves efficiency. A single fiber can carry terabits per second using WDM. A single cellular channel can serve many users using OFDMA. The more efficient the multiplexing, the more value from the spectrum. It is the hidden engine of telecom.