The present disclosure concerns a method and apparatus for measuring a sensor (10) comprising multiple optical resonators (11, 12) optically connected to a single optical output interface (16). The optical resonators (11, 12) are interrogated with a light input signal (Si). A light output signal (So) is measured from the optic al output interface (16) to determine a combined spectral response (Sa) covering a wavelength range (W) including a plurality of resonance peaks (λ1,i, λ2,j) for each of the optical resonators (11, 12). A Fourier transform spectrum (FT) of the combined spectral response (Sa) is calculated and a harmonic series of periodic peaks (n·f1) is identified in the Fourier transform spectrum (FT). The harmonic series of periodic peaks is filtered to obtain a filtered Fourier transform spectrum (FT1) and a sensor signal is calculated (X1) based on the filtered Fourier transform spectrum (FT1).