Selection of the region of operation of an optical filter formed by two Sagnac interferometers in series through the use of retarding plates

This work propose an array using a plate λ/4 as a way to get a phase difference equal to zero between the interferometers. Experimental results show that adjusting the orientation angles of the axis of the plate inside the loop, is possible to get the phase shift. Although exist a decreasing in the maxim transmission peak, is possible to reduce the time and difficulty of adjusting and achieve by mean of the temperature the need conditions to the filter tuning.