Self-referencing optical sensors and methods are described herein that can be used to detect bio-chemical interactions (e.g., biological binding of antigen-antibody pairs) that occur in for example a microplate. In one embodiment, the self-referencing optical sensor includes a substrate, a lower (reference) waveguide grating structure, a buffer layer and an upper (sensing) waveguide grating structure. This self-referencing optical sensor enables an optical interrogation system to detect a bio-chemical interaction independent of the effect of temperature by measuring a reference signal associated with the lower (reference) waveguide grating structure and measuring a sensing signal associated with the upper (sensing) waveguide grating structure. These two signals are then subtracted from one another to determine a sensing measurement that represents whether or not the bio-chemical interaction occurred that is independent of the effect of temperature. This is all possible because the self-referencing optical sensor has a lower (reference) waveguide grating structure with a thickness that was sized to make a rate of change of a lower resonant wavelength/temperature variation (.DELTA..lamda..sup.L/.DELTA.T) substantially equal to a rate of change of an upper resonant wavelength/temperature variation (.DELTA..lamda..sup.U/.DELTA.T). Several other embodiments of self-referencing optical sensors which have a specific structures and/or a specific compositions are also described herein.