Optical protection switch employing an interference filter

摘要

A protection facility is provided for use in an optical communications node that communicates with another optical communications node via first and second bidirectional communications paths respectively serving as a service path and protection path, in which a filter filters signals respectively received over the service and protection paths and generates a main signal and a complementary signal for each of the paths. A control unit then generates a Loss of Signal (LOS_A) indication for the service path if a SUM signal or DIFF signal respectively derived as a function of a sum of the main and complementary signals generated for the service path and difference between the main and complementary signals generated for the service path is less than a respective threshold value. A switch then invokes protection switching responsive to the presence of the LOS_A indication.