The DNN-based DBP scheme for nonlinear compensation and longitudinal monitoring of optical fiber links

In this paper, a double-effect DNN-based Digital Back-Propagation (DBP) scheme is proposed and studied to achieve the Integrated Communication and Sensing (ICS) ability, which can not only realize nonlinear damage mitigation but also monitor the optical power and dispersion profile over multi-span links. The link status information can be extracted by the characteristics of the learned optical fiber parameters without any other measuring instruments. The efficiency and feasibility of this method have been investigated in different fiber link conditions, including various launch power, transmission distance, and the location and the amount of the abnormal losses. A good monitoring performance can be obtained while the launch optical power is 2 dBm which does not affect the normal operation of the optical communication system and the step size of DBP is 20 km which can provide a better distance resolution. This scheme successfully detects the location of single or multiple optical attenuators in long-distance multi-span fiber links, including different abnormal losses of 2 dB, 4 dB, and 6 dB in 360 km and serval combinations of abnormal losses of (1 dB, 5 dB), (3 dB, 3 dB), (5 dB, 1 dB) in 360 km and 760 km. Meanwhile, the transfer relationship of the estimated coefficient values with different step sizes is further investigated to reduce the complexity of the fiber nonlinear damage compensation. These results provide an attractive approach for precisely sensing the optical fiber link status information and making correct strategies timely to ensure optical communication system operations.