Relay transmission apparatus

摘要

A relay transmission apparatus in which the effectiveness of a protecting function is improved by suppressing variation of an OSNR value of a signal regardless of the distance that the signal is transmitted. The relay transmission apparatus is comprised of a first regenerative relay unit, a second regenerative relay unit, and a protection process unit for extracting a signal component from each of the first and second regenerative relay units and selectively outputting either of the extracted signal components as a drop signal.