Wavelength division multiplexing (WDM) allows two or more wavelengths OF light to BE TRANSMITTED over DIFFERENT optical channels simultaneously in the same fiber. WDM (Wavelength Division Multiplexing) is two or more different wavelengths of optical carrier signals (carrying a variety of information), at the transmitter through Multiplexer (Multiplexer) together, and coupled to the same fiber for transmission, At the receiving end, the optical signals of various wavelengths are separated by Demultiplexer, and then further processed by the optical receiver to restore the original signal.
To put it simply, you can look at the figure below. In the traditional transmission mode, one fiber can only transmit the optical carrier signal carrying one kind of information, and if it is to be different services, countless different and independent fibers are needed for transmission. However, if the amount of business information is large, a large number of optical fibers need to be laid for transmission, which is a great challenge for wiring space and cost. The application of a WDM system can quickly solve the above problems. WDM system can carry a variety of formats of "business" signals, such as ATM, IP, etc., through the multiplexing, demultiplexing technology will be a variety of business signals through a fiber can be transmitted, greatly reducing the amount of fiber consumption, network expansion and development of the ideal expansion means. In the introduction of new broadband services, such as CATV, HDTV, B-ISDN, etc., only one additional wavelength is needed.
The basic structure of a general WDM system
The basic structure of WDM system is mainly divided into two ways: dual-fiber unidirectional transmission and single-fiber bidirectional transmission. Dual-fiber one-way means that all optical paths are transmitted in the same direction on a fiber at the same time, and different wavelengths carry different optical signals. At the transmitter, the composite is transmitted through a fiber, and at the receiver, the demultiplexing is performed to complete the transmission of multi-channel optical signals, and the reverse direction is transmitted through another fiber. The transmission in both directions is completed by two fibers, respectively. Single-fiber bidirectional means that the light path is transmitted in two different directions at the same time on a major fiber, and the wavelengths used are separated from each other to achieve full-duplex communication between each other.
The general WDM system is mainly composed of five parts: network management system, optical transmitter, optical relay amplification, optical receiver and optical monitoring channel.
In the simple WDM system, there are mainly transceivers, WDM wavelength division multiplexers, jumpers, and dark fiber components.
In the whole WDM system, optical wavelength division multiplexer and demultiplexer are the key components of WDM technology, and their performance has a decisive effect on the transmission quality of the system.
