Although optical fiber communication is the best for transmitting data at a high rate, we are trying to push the data rate even higher. While the fiber channel may be capable of transmitting terabitper- second data rates, no existing single communication system can make complete use of this speed. Adding more and more fibers to the system as a method of increasing speed is uneconomical as we know the global network is made of a large submarine cable networks that is expensive to modify. An alternative solution to this is Wavelength Division Multiplexing (WDM) where each modulated signal is transmitted at an individual frequency, allowing full duplex data transmission. In WDM systems the available fiber bandwidth is divided into separate channels with each channel carrying one signal, thus increasing the overall data rate without increasing the number of fibers. The data rate of each channel can be limited, but with many channels the total data rate is considerably higher. At the receiver end of the link, a de-multiplexer separates the wavelengths and routes them into different fibers, which all terminate at separate receivers. The spacing between the individual wavelengths transmitted through the same fiber serve as the basis for defining Dense WDM and Coarse WDM. For cost-effective solutions to their transport needs, Coarse WDM is becoming more widely accepted as important transport architecture.