The emergence of DWDM is one of the most recent and important phenomena in the development of fiber optic transmission technology. This tutorial will introduce the fundamentals of DWDM technology, such as the components, optical amplifiers used in DWDM system, etc.
Components and Operation
DWDM is a core technology in an optical transport network. The essential components of DWDM can be classified by their place in the system. On the transmit side, there are lasers with precise, and stable wavelengths. On the link, there is optical fiber that exhibits low loss and transmission performance in the relevant wavelength spectra, in addition to flat-gain optical amplifiers to boost the signal on longer spans. On the receive side, there are photodetectors and demultiplexers using thin film filters or diffractive elements. Besides these components, optical add/drop multiplexers and optical cross-connect components may be used.
The main job of optical fibers is to guide lightwaves with a minimum of attenuation (loss of signal). Multimode fiber and single-mode fiber are the general two categories of optical fiber in use today. Single-mode fiber has a much smaller core that allows only one mode of light at a time through the core. As a result, the fidelity of the signal is better retained over longer distances, and modal dispersion is greatly reduced. These factors attribute to a higher bandwidth capacity than multimode fibers are capable of. For its large information-carrying capacity and low intrinsic loss, single-mode fibers are preferred for longer distance and higher bandwidth applications, including DWDM.