abstract
- An optical back propagation (OBP) technique is investigated to compensate for nonlinear impairments in fiber optic communication systems with reconfigurable optical add-drop multiplexers (ROADMs). An OBP module consisting of an optical phase conjugator (OPC), amplifiers and dispersion-decreasing fibers (DDFs) fully compensates for the nonlinear impairments of a transmission fiber. The OBP module can be placed after each transmission fiber (inline OBP case) or at each network node (node OBP case). For a wavelength division multiplexing (WDM) system with 2400 km transmission distance and 32-quadrature amplitude modulation (QAM) format, inline OBP and node OBP bring Q-factor improvements of 4.9 dB and 5.6 dB as compared with linear compensation, respectively. In contrast, receiver-side digital back propagation (DBP) only provides 1.3 dB Q-factor gain, due to its incapability of mitigating inter-channel nonlinear effects in fiber optic networks.