An optical protection switch and a method for optical protection switching are provided. The optical protection switch includes a loop mirror-based optical switch with two circulators and a direction-dependent phase shifter in the loop mirror. The direction-dependent phase shifter introduces phase shifts in counter-propagating optical signals in the loop mirror such that either one of a first optical signal and a second optical signal are switched as an output optical signal. The direction-dependent phase shifter is controlled by a controller which initiates switching from the first optical signal to the second optical signal if a drop in power level is detected in the first optical signal and a corresponding drop in power level is not detected in the second optical signal and vice versa.