WedescribeandexperimentallydemonstrateameasuringtechniqueforMach–Zehnderinterferometer（MZI）basedintegratedphotonicbiochemicalsensors.OurtechniqueisbasedonthedirectmeasurementofphasechangesbetweenthearmsoftheMZI,achievedbysignalmodulationononeofthearmsoftheinterferometertogetherwithpseudoheterodynedetection,anditallowsustoavoidtheuseofcostlyequipmentsuchastunablelightsourcesorspectrumanalyzers.Theobtainedoutputsignalisintrinsicallyindependentofwavelength,powervariations,andglobalthermalvariations,makingitextremelyrobustandadequateforuseinrealconditions.Usingasilicon-on-insulatorMZI,wedemonstratethereal-timemonitoringofrefractiveindexvariationsandachieveadetectionlimitof4.1×10-6refractiveindexunits（RIU）.
