An optical interrogation system is described herein that can interrogate a label-independent-detection (LID) biosensor and monitor a biological event on top of the biosensor without suffering from problematical parasitic reflections and/or problematical pixelation effects. In one embodiment, the optical interrogation system is capable of interrogating a biosensor and using a low pass filter algorithm to digitally remove problematic parasitic reflections contained in the spectrum of an optical resonance which makes it easier to determine whether or not a biological event occurred on the biosensor. In another embodiment, the optical interrogation system is capable of interrogating a biosensor and using an oversampling/smoothing algorithm to reduce oscillations in the estimated location of an optical resonance caused by the problematical pixelation effect which makes it easier to determine whether or not a biological event occurred on the biosensor.