In some instances it is beneficial to utilize an apparatus comprising a compensating interferometer that modulates the phase of an input light signal to produce an output signal that is a superposition of an input signal and a phase shifted version of the input signal. One such instance is when a compensating interferometer is used to manipulate the output of a sensor array as described in U.S. Pat. No. 5,987,197. However, known compensating interferometers lack functionality that can be advantageous in processing optical signals.