Constantly increasing traffic demands the improving of spectral efficiency in core networks. In the same time, increasing of spectral efficiency can lead to an overall network power consumption due to necessity of additional signal regeneration. The 10 Gbps NRZ-OOK signal may be considered as one of the possible solutions in virtue of its relatively simple realization and high information transmission speed. Hence, this paper aims at spectral efficiency influence of 10Gbps NRZ-OOK signal on system power consumption and, as a result, on energy efficiency while guaranteeing the certain signal quality at the receiving node of an end-to-end connection.