In this paper, the design, fabrication and characterization of a sensor is presented, optimized for sensing changes of the absorption coefficient of a monomolecular transduction layer, while at the same time being insensitive to environmental absorption changes. A functional analysis of the device is given, relating the effect of technological uncertainties to systematic errors in the determination of the measurand. A physical implementation of the functional design based on dual mode interrogation, using a polarization converter and polarization splitter, is presented and fabricated. From a tolerance analysis, using the values of the applied SiON technology, it was derived that, over a range of 1 decade, this implementation allows for an inaccuracy of an uncalibrated sensor <10%. The performance characteristics of the individual subfunctions are given. Propagation losses are 1.6 dB cm^-1 for both TE and TM polarized light. The relative wavelength shift of the resonance wavelength of the fabricated (grating assisted) polarization converters to its intended value is only 0.002. Experimentally, a 30 times decrease in the sensitivity to the output signal for changes in the absorption of the outer medium, compared to a monomodal sensor, has been observed.