Multiplexing Technology (Mux): Principles and Implementation of Channel Multiplexing

# 1. Introduction

## 1.1 What is Multiplexing Technology (Mux)?

Multiplexing technology, commonly abbreviated as Mux, is a technique used to transmit multiple signals simultaneously within limited communication resources. In the realm of communication, channel multiplexing is a critical technology that enables the overlaying of multiple signals onto a single physical channel for transmission by employing appropriate multiplexing methods, thus enhancing channel utilization.

## 1.2 Why is Multiplexing Technology Needed?

With the rapid development of information technology, there is an ever-increasing demand for communication bandwidth. However, communication resources are not unlimited. If each signal were to be transmitted using a dedicated channel, it would lead to a waste of resources and inefficiency. Therefore, there is a need for an effective technology to multiplex multiple signals reasonably onto the same channel to improve resource utilization efficiency. Multiplexing technology emerged as the need arose, utilizing channel multiplexing to combine multiple signals in a reasonable manner, fully utilizing limited resources to meet the growing demand.

There are various ways to implement multiplexing technology, such as Time Division Multiplexing (TDM), Frequency Division Multiplexing (FDM), and Wavelength Division Multiplexing (WDM), each with its own characteristics and suitable scenarios. In the following chapters, we will delve into the principles and methods of channel multiplexing, as well as case studies of multiplexing technology applications across various domains.

# 2. Principles of Channel Multiplexing

Channel multiplexing is a technology that transmits multiple independent signal sources through the same physical link. Its fundamental principle involves separating multiple signals using different multiplexing techniques in terms of time, frequency, or wavelength, ***mon channel multiplexing technologies include Time Division Multiplexing (TDM), Frequency Division Multiplexing (FDM), and Wavelength Division Multiplexing (WDM). We will now explore the principles of these various channel multiplexing methods.

### 2.1 Time Division Multiplexing (TDM) Principle

Time Division Multiplexing is a technique that multiplexes multiple signals by time slots. In TDM, time is divided into several fixed time slots, each of which is used to transmit the data of one signal. For instance, if there are two signal sources A and B, and the TDM time slot is set to 1 second, then during the first time slot, only the data of signal A is transmitted; during the second time slot, only the data of signal B is transmitted; and this process is then repeated cyclically.

The advantage of TDM is that it can fully utilize the bandwidth of the signal sources, as each signal occupies the entire time slot during transmission. However, a drawback is that when there are many signal sources, the length of the time slots becomes very short, which can decrease transmission efficiency.

### 2.2 Frequency Division Multiplexing (FDM) Principle

Frequency Division Multiplexing is a technique that multiplexes multiple signals based on different frequencies. In FDM, the available frequency band is divided into several independent sub-bands, each of which is used to transmit the data of one signal. For example, if there are two signal sources A and B, FDM divides the frequency band into two sub-bands, one for transmitting the data of signal A and the other for transmitting the data of signal B.

The advantage of FDM is that it allows multiple signals to be transmitted simultaneously, with each signal occupying a different frequency, thus not interfering with one another. The downside is that it requires narrow signal bandwidths, otherwise, frequency band overlap could cause interference between signals.

### 2.3 Wavelength Division Multiplexing (WDM) Principle

Wavelength Division Multiplexing is a technique that multiplexes multiple signals based on different wavelengths. In WDM, the different wavelength light signals are separated using the properties of light and transmitted through optical fibers. For instance, if there are two signal sources A and B, WDM sets the wavelength of light signal A to λ1 and the wavelength of light signal B to λ2, then combine