Time division multiplexing is the process in which multiple signals are combining onto one pipe. TDM uses time slots to carry signals. The signals are clocked at a fixed rate so that the bits are interleaving via a serial link. TDM follows two processes which are conversion and multiplexing. During the conversion process, signals are being converted from analog to digital. Once the signals are converted, multiplexing takes place. In this process the data bits are fitted into time slots or channels. The range of the time slots will vary based on the type of transmission medium used. Copper lines can multiplex up to 2 64kps channels on one line. If the data is being multiplexed on a fiber line, it can go as high as 129,024 channels on one fiber line. There are two form of TDM. They are Synchronous TDM and Asynchronous TDM. In Synchronous TDM, the slot allotted to a device is fixed. In Asynchronous TDM, if the device does not have any data to transmit, it will not be give a time slot. TDM does work well with applications that require periodic transmission of data. For networks, TDM can be used for switched Ethernet to prevent loss of data packets and queuing latency. Some of the advantages of TDM are that it consumes less bandwidth and one channel can be used by multiple users. One disadvantage of TDM is that if a client does not use a time slot, it can cause resources to be wasted.

Wave division multiplexing is the newest form of multiplexing technology. This process involves multiplexing various colors of light onto fiber strands which will greatly increase the amount of bandwidth available for systems that use fiber optics. Each beam of light can carry signals from different multiplexers which in turn can transport 169,344 DS-0s of traffic on one strand of fiber. WDM is used among telecommunication companies since this allows them to expand their network without the need to add more fiber. The advantages of WDM are that it is scalable, meaning that would be no need to switch over to new technology since newer channels can be added. This would also be cost effective for clients that already use WDM systems since they only would need to lease part of a fiber to share the connection with others. WDM also does not need to rely on the protocol in order to transmit data. The major disadvantage of WDM is that it is expensive and complex. WDM is also vulnerable to variations in the amplitude as well as reflections. This would cause the requirements for the fiber cable connectors to be strict.

Both TDM and WDM utilize the same concept in regards to multiplexing. They both convert analog signals over to digital and transmit the data over channels or lambdas. There are some differences between the two types. WDM has the ability to transmit data over multiple channels on just one fiber strand. However, WDM is expensive as well as being very complex. TDM consumes less bandwidth and allows different users to be able to utilize the same channel. Though TDM is cost effective, it would not be able to conserve bandwidth if a time slot that is allotted to a device is not transmitting data. Both TDM and WDM play a large role in the telecommunications network and will also provide scalability in the future.

Works Cited:

Bischoff, Dominik. "Wavelength multiplexing: WDM and DWDM systems."

http://www.ittc.ku.edu/research/thesis/documents/hariprasad_sampathkumar.pdf

Sampathkumar, Hariprasad. "Using Time Division Multiplexing to support Real-time Networking on Ethernet."

http://www.n.ethz.ch/~dominikb/Texte/WDMFibreoptics.pdf