The key difference between FDM TDM and WDM is that FDM divides the bandwidth into smaller frequency ranges and each user simultaneously transmits data via a common channel in their frequency range. TDM allocates a fixed time slot to each user to send signals through a common channel, while WDM combines several light beams from several channels and combines them into a single light beam, then passes through a strand of fiber optics similar to FDM.
Data transmission is the process of sending data as signals from source to destination. Multiplexing is a data transmission technique. It consists of taking several signals and combining them into a composite signal so that it is transmitted over a communication channel. FDM, TDM and WDM are three multiplexing techniques.
What is FDM ??
Bandwidth is the total capacity of a channel to transmit data. In FDM, the full bandwidth is divided among users. Therefore, each user gets their own bandwidth or range of frequencies. In other words, all users can use the channel at the same time, but they have their own bandwidths or frequency ranges for data transmission.
On the sending side, all signals are combined into a single signal using a multiplexer. Then the signal crosses the channel. At the reception, there is a demultiplexer. It separates the composite signal to separate the signals. A drawback of this multiplexing technique is that, since all the signals are transmitted simultaneously, there is a possibility of crosstalk. In short, FDM divides the bandwidth and provides frequencies to users. It does not divide time between users.
What is TDM ??
In TDM, users can get full channel bandwidth to send signals but for a fixed time slot. It scales the time between users. Suppose that there are three users: u1, u2 and u3 and that the fixed time range is t0. First, u1 will get the full frequency bandwidth for t0 time. When u1 transmits data, other users cannot transmit data. Once this time has elapsed, u2 can transmit data for a time t0. When u2 transmits data, other users cannot transmit data. Then u3 transmits the data for t0 time.
In short, TDM divides time and not bandwidth between users. They can only transmit signals in the available time slot. Since only one signal is transmitted at a time, crosstalk in TDM is minimal.
What is WDM ??
Fiber-optic communication uses WDM. The concept of WDM relates to physics. When a beam of white light passes through a prism, it splits into individual colored light beams through the prism. Each beam of light has different wavelengths. This scenario also works vice versa. The individual color beams combine to generate a beam of white light.
The WDM combines several light beams from channels using a multiplexer and sends them in the form of a single light beam through a strand of optical fiber. On reception, the demultiplexer separates the single light into several light beams and sends them to their own channels. Overall, WDM is similar to FDM, but transmission takes place via fiber-optic channels. Therefore, multiplexing and demultiplexing involve optical signals.
What is the difference between FDM TDM and WDM?
| FDM is a transmission technique in which several data signals are combined for simultaneous transmission via a shared communication medium. | TDM is a transmission technique that allows several users to send signals on a common channel by allocating a fixed time slot to each user. | WDM is a transmission technique that modulates numerous data streams, optical carrier signals of variable wavelengths in a single light beam passing through a single optical fiber. |
| Functionality | ||
| The FDM divides the bandwidth into smaller frequency ranges. Antransmitsser transmits data simultaneously via a common channel in their frequency range. | TDM allocates a fixed time slot to each user to send signals via a common channel. The user obtains all the bandwidth in this time slot. | The WDM combines several light beams from several channels and combines them into a single light beam and sends them through a strand of optical fiber similar to FDM. |
| Stands for | ||
| FDM stands for Multiplexing Division by Frequency. | TDM stands for time-division multiplexing. | WDM stands for multiplexing length. |
| Type of signals | ||
| FDM uses analog signals. | TDM uses digital and analog signals. | WDM uses optical signals. |
Summary – FDM TDM vs WDM
The difference between FDM TDM and WDM is that FDM divides the bandwidth into smaller frequency ranges and that each user simultaneously transmits data via a common channel in their frequency range. combines several light beams from several channels and combines them into a single beam and sends them through a strand of optical fiber similar to FDM.
Reference:
1.Agarwal, Tarun et al. “What are the different types of multiplexing in a communication system?”. Buy Electronics and Electrical Projects in India, Apr 12, 2016. Available here
3. Frequency division multiplexing (FDM) and time-division multiplexing (TDM) / Multiplexing by FDM and TDM, simplified engineering, February 8, 2018. Available here
