Photonic interferometer based sensing

A method comprising;

• detecting and/or quantifying an analyte of interest in a sample using a sensing system, wherein
• the sensing system comprises a photonic integrated circuit comprising an integrated interferometer configured for spectroscopic operation that characterizes the analyte of interest in the sample by using spectral features of a spectral transfer function of the integrated interferometer,
• the integrated interferometer comprising at least a sensing arm and a reference arm, both the sensing arm and the reference arm having an exposable segment configured such that light passing through the exposable segment interacts with the sample, whereby the exposable segment of the reference arm has an optical path length which is smaller than twice the optical path length of the exposable segment of the sensing arm, wherein the exposable section of the sensing arm is configured to be selective to the analyte of interest, whereas the exposable section of the reference arm is configured to be not selective to the analyte of interest,
• wherein one or more of the reference arm or the sensing arm comprises a covered segment configured such that light passing through the one or more covered segments does not interact with the sample when the interferometer is in use,
• wherein an overall optical path length difference between the reference and the sensing arm is due in part to different lengths of the respective one or more covered segments of the sensing arm and the reference arm, and the overall optical path length difference is such that the spectral transfer function of the integrated interferometer has a period P not smaller than 0.5 nm and the sensing system has a spectral resolution smaller than or equal to P/2.