Wavelength translation and regeneration find applications in link extensions to overcome loss and dispersion limitations in network upgrades. For example, a 1310- nm legacy network can be converted to a DWDM network that would improve link capacity and network management without resorting to the expense of electrical multiplexing and the transmission of higher bit-rate signals. Link capacity is increased by converting many 1310-nm signals in different fibers to a corresponding number of 1550-nm DWDM channels, each operating at the original signal bitrate, that could be multiplexed optically into a single fiber and managed using current technologies such as reconfigurable add/drop multiplexers (ROADM).
An example of the type of practical problems that can be addressed with wavelength translation is shown in Figure 2. In this case, the number of bits transmitted between the networks is the same. The lower bit-rate signals are multiplexed optically and then transmitted using optoelectronics designed to handle the original bitrates. Alternatively, these lower-bit-rate signals can be multiplexed electrically to a higher rate so that higher bit-rate optoelectronics must be used. With the signals translated to 1550 nm using a proper optical source (e.g., a narrow-linewidth laser), the stage is set for the use of optical amplification, dispersion compensation, and other signal-massaging techniques required to transmit over longer distances.