ABSTRACT
Optical signals propagating in fiber-optic transmission systems are affected by several effects, namely amplified spontaneous emission from optical amplifiers, chromatic dispersion, polarization-mode dispersion, and nonlinear phenomena. Considering the impairments imposed by these effects, the use of signal regenerators becomes necessary in order to extend the maximum transmission distance of the systems. The signal regeneration is conventionally performed by optical-electrical-optical regenerators that involve signal conversion between the optical and electrical domains and noise removal on the electrical signal. A noninverting mode can also be achieved by offsetting the center frequency of output bandpass filter (BPF) away from the original clock wavelength, in order to transmit only cross-phase modulation (XPM) generated frequencies. All the three major nonlinear effects, SPM, XPM, and four-wave mixing (FWM), can be used to realize 2R regeneration. Among them, SPM is most often used.
