The maximum number is reached, although not all are represented here. A wavelength translator allows any optical traffic to be supported by the WDM system. What gets in the way of light transmission is attenuation and dispersion. However, special fiber means extra cost. A DCM is a length of fiber that distorts the light pulses in a manner that creates a better pulse shape at the other end of the link.
Direct modulation means that the laser is switched on and off.
The technology to do this is cheap but would not be effective for long distances. However, long distances can be achieved with this. History of Transmission 2. Transmission Signal Parameters 4. Types of Transmission Networks 5.