Device comprising: - at least one optical interferometric sensor, as a first Mach-Zehnder interferometric sensor with a large FSR from 10s of nanometers to many 100s of nanometers, wherein a plasmonic waveguide is incorporated as a transducer element planar integrated on Si 3 N 4 photonic waveguides said Si 3 N 4 photonic waveguides being Photonic waveguides with a high index silicon nitride strip (303, 603), which is sandwiched between a low index oxide substrate, and a low index oxide superstrate, - Optical coupling structures (102, 109) at both ends of the Mach-Zehnder interferometric sensor acting as the optical I/Os; - an Optical splitter and an optical combiner for optical splitting at the first junction of said first Mach-Zehnder interferometric sensor and optical combining at the second junction of said Mach-Zehnder interferometric sensor, particularly a Y-junction, directional coupler or multi-mode interference coupler; wherein the plasmonic waveguide developed in the upper branch of said first Mach-Zehnder interferometric sensor confines light propagation through coupling to Surface Plasmon Polaritons at the metal-analyte interface, characterized in that it comprises an additional optical interferometric element, as an additional Mach-Zehnder interferometer being arranged in a reference arm of said first Mach-Zehnder interferometric sensor, both said Mach-Zehnder interferometers and comprising thermo-optic phase shifters (104, 106) for optimally biasing said interferometers; further comprising an overall chip - said additional Mach-Zehnder interferometer with its phase shifter having the function of a variable optical attenuator, deploying an optical splitter and an optical combiner for optical splitting at the first junction of said additional Mach-Zehnder interferometer, and optical combining at the second junction of said additional Mach-Zehnder interferometer, wherein the Thermo-optic phase shifters (104, 106) tune the phase of the optical signal in the reference arm (104, 106) of each said Mach-Zehnder interferometers (MZI1, MZI2 - VOA); wherein said Thermo-optic phase shifters are formed by depositing two metallic stripes parallel to each other on top of a section of the photonic waveguide and along the direction of propagation of light. - at least one optical interferometric sensor, as a first Mach-Zehnder interferometric sensor with a large FSR from 10s of nanometers to many 100s of nanometers, wherein a plasmonic waveguide is incorporated as a transducer element planar integrated on Si 3 N 4 photonic waveguides said Si 3 N 4 photonic waveguides being Photonic waveguides with a high index silicon nitride strip (303, 603), which is sandwiched between a low index oxide substrate, and a low index oxide superstrate, - Optical coupling structures (102, 109) at both ends of the Mach-Zehnder interferometric sensor acting as the optical I/Os; - an Optical splitter and an optical combiner for optical splitting at the first junction of said first Mach-Zehnder interferometric sensor and optical combining at the second junction of said Mach-Zehnder interferometric sensor, particularly a Y-junction, directional coupler or multi-mode interference coupler; wherein the plasmonic waveguide developed in the upper branch of said first Mach-Zehnder interferometric sensor confines light propagation through coupling to Surface Plasmon Polaritons at the metal-analyte interface, characterized in that it comprises an additional optical interferometric element, as an additional Mach-Zehnder interferometer being arranged in a reference arm of said first Mach-Zehnder interferometric sensor, both said Mach-Zehnder interferometers and comprising thermo-optic phase shifters (104, 106) for optimally biasing said interferometers; further comprising an overall chip - said additional Mach-Zehnder interferometer with its phase shifter having the function of a variable optical attenuator, deploying an optical splitter and an optical combiner for optical splitting at the first junction of said additional Mach-Zehnder interferometer, and optical combining at the second junction of said additional Mach-Zehnder interferometer, wherein the Thermo-optic phase shifters (104, 106) tune the phase of the optical signal in the reference arm (104, 106) of each said Mach-Zehnder interferometers (MZI1, MZI2 - VOA); wherein said Thermo-optic phase shifters are formed by depositing two metallic stripes parallel to each other on top of a section of the photonic waveguide and along the direction of propagation of light.