Mathematical models of wavelength division multiplexing devices
With the Intemet booming in recent years, the demand for high-speed transmission over communications networks is increasing at a tremendous rate. There has been a lot of effort trying to explore technologies to enhance the capacity and the utility of transmission media. Since it is well-known that the transmission capacity of optical fiber is enormous and that optical fibers are getting cheaper and cheaper, people have been trying to find more effective ways to utilize the available bandwidth. Wavelength division multiplexing (WDM) is one such technology. It is used to transmit multiple wavelengths of light in a single optical fiber (Figure 1.1 ). WDM takes advantage of the 25,000 GHz capacity in the passband of light of optical fibers, reaching a capacity 1,000 times greater than the traditional multiplexing technology, time division multiplexing (TDM), which can only carry around 2.5 gigabit per second in a single fiber. It can be expected that as optical technologies become more and more mature, the price of optical devices will drop and communications networks in the fiiture will be dominated by optical networks.